Responses to Coastal Erosio in Alaska in a Changing Climate

Transcription

1 Responses to Coastal Erosio in Alaska in a Changing Climate A Guide for Coastal Residents, Business and Resource Managers, Engineers, and Builders Orson P. Smith Mikal K. Hendee

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3 Responses to Coastal Erosio in Alaska in a Changing Climate A Guide for Coastal Residents, Business and Resource Managers, Engineers, and Builders Orson P. Smith Mikal K. Hendee Alaska Sea Grant College Program University of Alaska Fairbanks SG-ED-75

4 NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Elmer E. Rasmuson Library Cataloging in Publication Data: Smith, Orson P. Responses to coastal erosion in Alaska in a changing climate : a guide for coastal residents, business and resource managers, engineers, and builders / Orson P. Smith ; Mikal K. Hendee. Fairbanks, Alaska : Alaska Sea Grant College Program, University of Alaska Fairbanks, p.: ill., maps ; cm. - (Alaska Sea Grant College Program, University of Alaska Fairbanks ; SG-ED-75) Includes bibliographical references and index. 1. Coast changes Alaska Guidebooks. 2. Shore protection Alaska Guidebooks. 3. Beach erosion Alaska Guidebooks. 4. Coastal engineering Alaska Guidebooks. I. Title. II. Hendee, Mikal K. III. Series: Alaska Sea Grant College Program, University of Alaska Fairbanks; SG-ED-75. TC330.S ISBN doi: /rceacc.2011 Alaska Sea Grant College Program, University of Alaska Fairbanks. All rights reserved. Credits This book, SG-ED-75, is published by the Alaska Sea Grant College Program, supported by the U.S. Department of Commerce, NOAA National Sea Grant Office, grant NA10OAR , projects A/75-02 and A/161-02; and by the University of Alaska Fairbanks with state funds. Sea Grant is a unique partnership with public and private sectors combining research, education, and technology transfer for the public. This national network of universities meets changing environmental and economic needs of people in our coastal, ocean, and Great Lakes regions. The University of Alaska is an affirmative action/equal opportunity employer and educational institution. For information on undergraduate and graduate opportunities in marine biology, fisheries, oceanography, and other marine fields at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences, visit NOAA and the publisher do not necessarily endorse all opinions and products mentioned in this book. Book design, layout, and cover design by Dave Partee; project management and editing by Sue Keller; and project coordination by Kurt Byers, all of Alaska Sea Grant. Cover photo: U.S. Geological Survey researcher Benjamin Jones measures erosion on Alaska s arctic coast. Note the collapsed block of ice-rich permafrost on left. Courtesy Christopher Arp, USGS. U.S. DEPARTMENT OF COMMERCE Alaska Sea Grant College Program University of Alaska Fairbanks P.O. Box Fairbanks, Alaska Toll free (888) (907) Fax (907)

5 Table of Contents Preface... iv Introduction... 1 Chapter 1. Shoreline Processes... 5 Chapter 2. Alaska Coastal Settings Chapter 3. Coastal Erosion Response Options Chapter 4. Revetments and Seawalls Chapter 5. Beach Nourishment and Beach Groins Chapter 6. Permitting Requirements Concluding Remarks References Cited Glossary Index

6 iv Preface... it is well that men of science should not always expound their work to the few behind a veil of technical language, but should from time to time explain to a larger public the reasoning which lies behind their mathematical notation.... Sir George Howard Darwin, son of biologist Sir Charles Darwin, from The Tides and Kindred Phenomena in the Solar System (1898) A nationwide program sponsored by the U.S. Army Corps of Engineers during the 1970s tested and reported on low-cost measures to control coastal erosion. Several trials of selected shore protection works were built in Alaska as a part of the Low Cost Shore Protection program. Stocks of resulting brochures and booklets were depleted within a few years. They were aimed at landowners and others with interest in preventing loss of valuable personal and community property to coastal erosion. This 2011 book reaches toward the same group with updated and more comprehensive advice on options now available. Responses to coastal erosion explored in the pages that follow include choices for land development that avoid active erosion and thus reduce the risk of later losses. Also included are choices for communities to prevent losses to contiguous coastal property and entire reaches of coastline. This publication is aimed primarily at property owners and community leaders. Engineers and builders who will design and construct erosion control projects are referred throughout to pertinent technical literature. Acknowledgments The thorough and thoughtful comments and suggestions of our reviewers made this book better. The review efforts of the following people are gratefully acknowledged: Ken Eisses (U.S. Army Corps of Engineers), David Kriebel (U.S. Naval Academy), Harvey Smith (Alaska Department of Transportation and Public Facilities), Gabriel Wolken (Alaska Division of Geological and Geophysical Surveys), Roselynn Ressa (Alaska Department of Natural Resources), and Gary Williams (Kenai Peninsula Borough). We also appreciate the sponsorship and patient encouragement of the Alaska Sea Grant College Program.

7 Responses to Coastal Erosion in Alaska in a Changing Climate 1 Introduction... A great opportunity now exists for Alaska and its people to design for and live with natural processes rather than confront them head on. Owen Mason in Living with the Coast of Alaska (1997) Alaska Coastal Development Trends Native Alaskans lived along the shoreline for thousands of years before Alaska s transition to a society with modern economic pressures. Many Alaska coastal communities trace their origins to ancient Native settlements where people seasonally gathered for a subsistence advantage unique to the location. Today, marine industries, tourism, personal recreation, and a natural desire of Alaskans to live by the sea drive coastal developments all around the vast and complex shores of the state. Alaska s population is growing, and growth is bringing pressure of visitation and development on beaches and bluffs from Ketchikan to Barrow and on to the arctic Canadian border. A significant fraction of older coastal communities in Alaska grew from seasonal subsistence camps that existed in generations past for bountiful hunting and fishing by small groups. The twentieth century brought a modern standard of living to these beach sites with housing, utilities, schools, community buildings, airports, harbors, community roads, and other construction. Populations once very small have multiplied and community infrastructure has spread in response. Locations were not chosen to accommodate substantial community growth or to avoid eventual problems with shoreline retreat. Homes and public works are now threatened by erosion in Shishmaref, Kivalina, Barrow, Wainwright, Point Hope, Dillingham, and many other honored Alaska hometowns. These most intensely troubled coastal communities have histories of well-meaning, but sadly failed, erosion control projects. Threats of erosion have become so severe in some cases that complete village relocations are now planned, at staggering expense. The largest coastal resident concentrations and most rapid population growth are in southcentral Alaska, surrounding the commercial and transportation hub at Anchorage. Statistics published by the Alaska Department of Labor and Workforce Development reveal that the

8 2 Introduction Anchorage and Matanuska-Susitna region now holds over 50 percent of the state s population. The adjacent region, composed of the Kenai Peninsula and Kodiak Island boroughs and the Valdez-Cordova census area, houses another 12 percent. Twenty-year projections predict this concentration of population will be maintained with over a half million people living on or within easy reach of Cook Inlet and the northern Gulf of Alaska shorelines. This same coast is sought by tourists arriving on cruise ships in coastal towns and by air at Anchorage. The economically important visitors see shoreline vistas from trains, buses, rental cars, motor homes, charter planes, air taxis, excursion boats, bike trails, and hiking paths. Coastal towns hold festivals and strive by a variety of means to draw ever-greater numbers of tourists to contribute to their local economies. Similar pressures from tourism exist in southeastern Alaska, where another 12 percent of Alaskans live and work. This region also has coastal development related to commercial fishing, timber, and other resource export industries. Southwestern Alaska, with about 6 percent of the population, enjoys some tourism, but its coast is most significantly affected by the commercial fishing industry. While Alaska s northern region holds only 4 percent of the state s population, it includes the erosion-affected Native Alaska coastal communities mentioned above and valuable oil and gas developments along the Beaufort and Chukchi sea coasts. All coastal regions of Alaska are accumulating issues, concerns, and controversies regarding impacts of shoreline development and threats of erosion. Lessons from Outside Economic and recreational opportunities of coastal living appeal to people everywhere. According to Don Hinrichsen (Coastal Waters of the World: Trends, Threats, and Strategies, 1998), over half of the world s population now lives and works within 120 miles (200 kilometers) of the seashore. Almost 75 percent of Americans may live near the coast by Populations in urbanized coastal zones, such as from Washington, D.C., to Boston, already exceed 2,500 people per square kilometer. Clashes with nature in such concentrations of people are inevitable. The seashore is particularly vulnerable to disruption of its natural cycles by construction of homes, shops, and other works for human residency. The tenuous equilibrium of most natural shorelines cannot abide the impacts of humans without change. Once disrupted, nature

9 Responses to Coastal Erosion in Alaska in a Changing Climate 3 forces a new equilibrium that shows no mercy to private, commercial, or public investments. Tracts of undeveloped coastal property available for home building are rare in the municipality of Anchorage and are disappearing fast in the adjacent Matanuska-Susitna and Kenai Peninsula boroughs. These most populous of Alaska s regional governments are facing pressures familiar to their counterparts on the Atlantic and Gulf of Mexico coasts of the Lower 48. People want to see the ocean from their living rooms and are building homes close enough to the shore to be threatened by erosion. A will to constrain this trend grows as one coastal home after another reaches the edge of the bluffs lining Cook Inlet. Objectives of This Book This book is written to guide present and prospective coastal property owners and local government officials toward good advice on erosion response options. Defense of home and property is viewed by many as a hallowed right, especially by independent-minded Alaskans. Unfortunately, property owners seldom have sufficient personal knowledge of coastal processes and specialized engineering considerations to make an informed choice among alternative actions in the face of attack by the sea. Furthermore, most property owners have limited financial means to construct shore protection. To realize that the ocean threatens their beloved place on the coast and then to see their hard-earned savings go to build inefficient, ineffective, or worse, even harmful works is a nightmare scenario for coastal residents. The language of coastal scientists and engineers is introduced in the pages that follow, and a glossary of coastal processes and engineering terms is included. Pros and cons of various erosion responses to shore protection designs are summarized, including possible long-term effects. Guidance to those contemplating purchase of coastal property is also offered in the context of recognizing hazards and assessing risk before serious commitment. Coastal managers in public service will gain useful insight from this publication. Local and regional governments must spread their resources and often place heavy burdens of responsibility on those who review permit applications to build on the coast. The guidelines offered here will help with evaluation of proposed coastal developments from a public interest perspective.

10 4 Introduction The Coastal Zone Management Act, first passed in 1972 and since amended, was administered by the Alaska Department of Natural Resources. The Alaska Coastal Management Program provided communities with a framework to plan wise development (see dnr.state.ak.us/acmp/). Representatives, who were elected by Alaskans, in 2011 voted to discontinue the Alaska Coastal Zone Management Program. Advice presented in this book is consistent with the Coastal Zone Management Act and is meant to be useful in public stewardship of Alaska s coastal resources. A good engineering report will address a variety of alternatives. Coastal engineering is a risky business and promises of certain success with a single alternative deserve suspicion. Engineers in general practice should consult with an experienced coastal specialist. 1 Nonresident coastal experts may place too much weight on successes and failures that took place elsewhere, and should be given time and resources to thoroughly investigate local conditions. Those who hire engineers must ask for appropriate analyses and be able to interpret presented findings. Engineers and others reading this book can review basics of coastal processes and the pros and cons of erosion response alternatives, before they refer to technical guidance that is cited. 1 The Academy of Coastal, Ocean, Port, and Navigation Engineers (ACOPNE), created in 2010 under the auspices of the American Society of Civil Engineers, specifies academic and practical credentials of those awarded a Diploma of Coast Engineering by the Academy. See acopne/.

11 CHAPTER1 Shoreline Processes In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth. Rachel Carlson, oceanographer Wind and Waves Coastal erosion is almost always caused by the turbulence of waves breaking in shallow water by the shore. This is true for Alaska shores, and coasts around the world. Beach sediment grains are put in motion within the surf zone and moved offshore, onshore, or along the shore (longshore) left or right down the coast. Water levels affect the location of the surf zone. Extreme high water conditions, caused by tides, storm surge, or combinations of the two, inundate coastal land normally above the reach of wave-induced sediment transport. Coastal currents, including tidal and wind-driven currents, affect wave behavior, and waves are the dominant force for coastal change. Waves are generated by wind blowing across the sea surface, often far out to sea. Factors that control wave characteristics include average wind speed, the duration of wind at a given speed, and fetch, or the open-water distance over which the wind blows. Faster winds generate higher waves. The process takes some time; therefore hours may go by before waves reach a maximum height in steady wind conditions. Bays, fjords, and sounds have limited fetches that constrain wave growth. Since waves usually follow the direction of the generating wind, wind direction with respect to the coast is an important factor regarding 5

12 6 Chapter 1 Shoreline Processes coastal erosion. Winds blowing away from the coast generate waves, but those waves travel away from the coast and cause no harm to the coast they leave behind. Waves moving toward shore may be constrained by the fetch in that direction, perhaps due to the shelter of a cape or headland. A wind rose is a diagram that summarizes wind speed and direction trends at a given site. Wind roses are useful to identify critical wind sectors (Figure 1-1). While one wind direction may prevail, another may bring the most damaging storm winds. Many coastal locations have a seasonal change in a prevailing direction, which will appear as two different, possibly opposing, dominant bars on a wind rose. Prevailing winds in Seward, Alaska, are from the south in summer and from the north in winter. Waves are characterized by their height and length (Figure 1-2) and by their period. Wave period is the time for one wave to travel past a fixed point. An easy way to observe average wave period is to time the passage of eleven wave crests or troughs (10 wavelengths) and divide % % 10% % Figure 1-1. Wind rose for Nikiski, Alaska, showing two sectors of prevailing wind direction: from the northeast and from the southwest along the axis of Cook Inlet. The radial scale indicates the fraction of winds from a sector during the period of record. Each alternating color in a radial band represents a 10-knot increment of speed. The length of a single color is on a scale of percent occurrence. Wind records are available from the NOAA National Climatic Data Center at

13 Responses to Coastal Erosion in Alaska in a Changing Climate 7 Crest SWL L H Trough d Figure 1-2. Sketch of wave parameters including wavelength (L), wave height (H), and water depth (d) of the Still Water Level (SWL). The horizontal arrow shows the direction of wave propagation past a hypothetical piling (brown vertical bar). The time for two successive crests to pass is the wave period. the result by ten. Waves of shorter wavelength have periods of a few seconds. Longer waves or swells have periods of ten seconds or more. Waves generated in deep water have characteristics that change as they reach shallow water. Waves approaching the shore become slower and their wavelengths decrease as depths diminish to less than half the deepwater wavelength. Transformation of wave characteristics from deep to shallow water is called shoaling. A depth is eventually reached that is too shallow for the waveform to remain stable and the crest cascades forward either as foam (spilling breaker, Figure 1-3) or as a tube (plunging breaker). The form of the breaking wave is affected by the wave height and period and by the slope of the beach. Waves after breaking still have energy and push up the slope of a beach or structure to a height known as runup. Wave runup is a vertical distance above the Still Water Level that defines the highest and maximum shoreward contact of a wave. Specialists predict wave generation and transformation using equations or, more precisely, numerical models. Figure 1-4 illustrates numerically simulated wave refraction. Refraction occurs when waves approach the shore at an angle, and differential slowing along a wave crest causes the wave to bend in to be more parallel to the shoreline. Wave-induced longshore sediment transport occurs in the direction at

14 8 Chapter 1 Shoreline Processes Figure 1-3. Spilling breakers near Kivalina, Alaska, July Orson Smith photo. Seawall Rigtenders dock Figure 1-4. Numerical model results showing wave refraction at Nikiski, Alaska. Red lines and shades of blue show contours of decreasing depth shoreward. Small black arrows (wave rays) indicate directions wave crests are traveling from deeper water at left to shallow water at right, showing how refraction bends waves to travel almost straight in to shore. Large white arrows are superimposed to highlight trends.

15 Responses to Coastal Erosion in Alaska in a Changing Climate 9 which refracted waves approach the shore, since a bit of longshore wave direction remains at the point of breaking. Wave energy spreads into the shadow zone behind an impermeable barrier by a process called diffraction. Diffraction allows some wave energy to wrap around into the lee or shadow zone behind a barrier (Figure 1-5). Vertical walls reflect wave energy back toward the sea. Reflected waves interact with incoming waves causing a choppy sea surface, increased wave height, and extreme turbulence immediately seaward of the wall. Boat and ship wakes closely resemble wind-generated waves, but are created in discrete groups. The energy in these wave groups is dispersed as the waves travel outward in a direction oblique to the vessel course (Figure 1-6). Shorelines along busy waterways with many vessels constantly passing each other can experience significant wave energy at the shore from boat wakes. Once generated, boat and ship wakes are transformed by refraction, shoaling, and diffraction similar to windgenerated waves. For more information on wave generation, transformations, and breaking, see the Coastal Engineering Manual at army.mil/, Part II, Chapters 1-5. Useful printed references on ocean Figure 1-5. Waves coming in from the bottom of the photo diffract in a circular pattern behind a spit at an inlet between two Chukchi Sea barrier islands. Orson Smith photo.

16 10 Chapter 1 Shoreline Processes Figure 1-6. Sketch of vessel-generated waves (solid lines) traveling along and outward from the vessel s course (dashed line). waves are also available at libraries and through publishers of academic textbooks. Tides Regular water level changes due to tides are familiar to those who frequent the coast. Tides are caused by the gravity of the moon and sun tugging at the seawater that covers over 71 percent of the earth s surface. The moon s gravity is the strongest tide-generating force, and a bulge of ocean water follows the moon in its orbit about the earth (Figure 1-7). When continents (29 percent of the earth s surface) are in the way, the effect of the bulge of water is similar to shoaling and refraction of wind-generated waves. Earth N Bulge of water slung away from moon Equator Earth s axis + CG Bulge of water pulled toward moon Moon S Moon s orbit about earth Figure 1-7. A hypothetical water-covered earth has bulges pulled toward the moon and slung away from the earth-moon center of gravity (CG), which results in two high tides each day as the solid earth in effect spins beneath the water bulges.

17 Responses to Coastal Erosion in Alaska in a Changing Climate 11 The moon does not orbit the earth in the plane of the equator, which results in two unequal high tides and two unequal low tides each day in many places along the coasts of the continents (Figure 1-7). The Gulf of Alaska coast along southeast and southcentral Alaska and the southern Bering Sea coast have relatively high tide ranges with two high tides each day, one significantly higher than the other. Likewise, this region experiences two low tides each day, one significantly lower than the other. The northern Bering, Chukchi, and Beaufort seas have relatively small tide ranges. Tide ranges in long estuaries like Cook Inlet grow as tidal energy is squeezed by constricting landforms and reducing depths. The long-term average of the lowest of daily low tide level, called Mean Lower Low Water (MLLW), is the reference elevation or datum from which depths are noted on maps and nautical charts. The long-term average of all high tides (maximum daily water levels), called Mean High Water (MHW), is the datum above which ground elevations on topographic maps are measured. Other datums not based on tides are also used for topography, such as NGVD1929 and NAVD1988. Mean Higher High Water (MHHW), the long-term average of the highest of daily high tides, is frequently used by engineers to represent high tide water levels. The difference between MHHW and MLLW is the diurnal tide range at a given coastal site. Other commonly used tidal parameters include Mean Low Water (MLW), the average of low tide levels; Mean Tide Level (MTL), the average of MHW and MLW; and Mean Sea Level (MSL), the average of hourly tide elevations. Both his- Table 1-1. Water level statistics relative to Mean Lower Low Water for Nome, Alaska. NOAA ( Datum Value Description Maximum 12.2 ft Highest Water Level Max Date 6 October 1992 Date of Highest Water Level MHHW 1.5 ft Mean Higher High Water MHW 1.4 ft Mean High Water MTL 0.8 ft Mean Tide Level MSL 0.8 ft Mean Sea Level MLW 0.3 ft Mean Low Water MLLW 0.0 ft Mean Lower Low Water Minimum 2.2 ft Lowest Water Level Min Date 7 January 2001 Date of Lowest Water Level

18 12 Chapter 1 Shoreline Processes NOAA/NOS/CO-OPS Verified Water Level vs. Predicted Plot Nome, Norton Sound, AK from 2005/09/ /09/ Height (Feet relative to MLLW) /13 00:00 09/13 08:00 09/13 16:00 09/14 00:00 Date/Time (GMT) 09/14 08:00 09/14 16:00 09/15 00:00 Predicted WL (Obs - Pred) Observed WL Figure 1-8. Tide information shows the differences between predicted tide and measured water levels over a two-day period at Nome, Alaska, during a damaging storm surge. NOAA co-ops.nos.noaa.gov/. torical and predicted tides are available from the National Oceanic and Atmospheric Administration (NOAA) and predictions are published by others in printed and electronic forms (see Table 1-1 and Figure 1-8). Tides do not significantly respond to weather patterns; thus waves and wind-induced water level changes are superimposed on the tides. For more information on tides, tidal datums, and tide predictions, see the NOAA Tides and Currents website at gov/. For more information about datums and earth geometry, see the National Geodetic Survey website at For more information on nautical charts of Alaska waters, see the NOAA chart websites at and noaa.gov/. For more information on topographic maps of Alaska coasts, see the U.S. Geological Survey (USGS) website at gov/. Storm Surge Strong winds drag water by surface friction to pile up against the shore, causing a water level increase during a storm s passage. This windinduced water level increase, called storm surge, subsides once the storm has passed and wind forces are relaxed. The temporary superelevation of the water allows waves to travel inland and impact areas

19 Responses to Coastal Erosion in Alaska in a Changing Climate 13 otherwise beyond direct reach of the sea. Figure 1-8 shows the difference between predicted tides and measured storm surge water levels at Nome, Alaska. For more information about storm surge causes and effects, see the website of the Federal Emergency Management Agency (FEMA) at the FEMA Coastal Construction Manual at and the Coastal Engineering Manual at Media/1/8/2/CEM_Part-II_Chap-5.pdf. Sea Level Rise Sea level rise is associated with global warming primarily by melting of glacier ice and by thermal expansion of ocean water. Much of Alaska was covered by glaciers during the last ice age and that land is still rising in relief from the weight of glacier ice. Southeast and southcentral Alaska coasts are rising, and the sea level relative to land will fall in these regions for the next century or more. These regions of Alaska are seismically active, however, and a single event like the March 1964 Great Alaska Earthquake can cause huge areas to almost instantly subside or rise more than centuries of sea level rise or glacial rebound (Figure 1-9). Sea level rise is a greater concern in arctic Alaska, where low-lying coastal plains are vulnerable to relatively small changes in sea level and may dramatically subside from melting permafrost. Figure 1-9. Tree stumps at Lowell Point near Seward, Alaska, indicate vertical subsidence of several feet that occcurred in March 1964 during the Great Alaska Earthquake. Sue Lang photo.

20 14 Chapter 1 Shoreline Processes For more information on sea level rise and other aspects of climate change, see the Environmental Protection Agency (EPA) website epa.gov/climatechange/, which includes links to many other sources. For more information on earthquakes in Alaska, see the USGS website at For more information on permafrost in Alaska and related climate change impacts, see the websites of the Arctic Climate Impact Assessment at and the U.S. Arctic Research Commission at Shoreline Sediment Transport Sand and other beach materials are moved at the shoreline primarily by wave action. The direction of sediment movement may be in the onshore-offshore (cross-shore) direction or it may be in the longshore direction. Accumulated effects of longshore sediment transport, including coastal erosion, result from annual average wave action. Waves from a prevailing direction push sediment in the surf zone in the direction of wave travel (Figure 1-10). Cross-shore sediment transport tends to be a seasonal cycle, but may be dramatic during a single severe storm. Winter weather is windier Direction of longshore sediment transport Figure Waves are approaching this Chukchi Sea shoreline, near Kivalina, Alaska, from the northwest and are moving sediments to the south along the shore where the waves are breaking. Orson Smith photo.

21 Responses to Coastal Erosion in Alaska in a Changing Climate 15 Bluff face Higher, wider summer beach Winter longshore berm Narrow winter beach Figure Features along the profile of a typical beach associated with seasonal cross-shore wave-induced sediment motion. with more storms than summer in most places, including Alaska. A stormy winter wave climate tends to push sediments offshore to form an underwater bar or berm along the shore at the limit of significant wave influence. Lower, steadier summer waves tend to push sediment from the bar back up to the beach. This classic pattern of beach behavior isn t always obvious on Alaska shores, such as on arctic coasts where in winter sea ice prevents waves from reaching the shore. Nevertheless, summer-winter patterns exist and may be associated with typical shoreline profile features shown in Figure A single very severe storm may disrupt the seasonal cycle and require many years to recover the former pattern or establish an entirely new equilibrium. Most shorelines eventually experience erosion. Wave-induced longshore sediment transport is sometimes called littoral drift, and the band of shallow water along shorelines where sediments are influenced by wave action is known as the littoral zone. Longshore transport will eat away at the shoreline unless sufficient sediment is arriving from outside the segment of interest. The littoral zone is a river of sand between capes, submarine canyons, river mouths, and other features that define a littoral cell. A littoral cell begins where longshore sediment supply first occurs and ends where longshore transport is lost, such as to a submarine canyon. A useful coastal zone management technique involves identification of littoral cells along the coast in terms of their sediment source and sink (i.e., beginning and end), types of coastal sediments in motion, and

22 16 Chapter 1 Shoreline Processes average rates of longshore and cross-shore transport within the cell. Rivers and streams contribute sediment in the littoral zone. Eroding bluffs in Alaska contribute sediment. The sediment budget approach has been accomplished in most coastal states of the United States, but not in Alaska as of For more information on littoral cells, coastal sediment budgets, and coastal processes see the USGS websites c1075/ and Sea Ice Sea ice at the shore can be an agent of erosion in northern Alaska, but more often forms an armor to protect the shore. Offshore ice prevents growth of waves. Shorefast ice armors the beach against wave attack. A current fear for global warming impacts is that receding ice cover will allow more wave growth in arctic seas that will lead to increased coastal erosion. Increased wave energy at the coast may result in erosion at some critical locations as new sediment budgets are achieved in nature. Other sites may see accretion as sediment arrives in increasing rates from nearby rivers or from adjacent eroding shorelines. For information on ice forms and classification, see the NOAA Observers Guide to Sea Ice at book_shelf/695_seaice.pdf.

23 CHAPTER2 Alaska Coastal Settings To the lover of wilderness, Alaska is one of the most wonderful countries in the world.... John Muir, naturalist Alaska has an estimated 47,300 miles of tidal shoreline, including its many thousands of islands and inlets. This is significantly more shoreline than all contiguous U.S. coastal states combined. The nature of this shoreline is extremely varied from rocky promontories of southeast Alaska to broad coastal plains and permafrost shores of the Beaufort Sea coast. Mason et al. (1997) describe major geological features and coastal trends along the Alaska coast. Features pertinent to erosion concerns are discussed in this chapter. Coastal settings of Alaska are divided here into three major geographic regions (Figure 2-1): Gulf of Alaska, Bering Sea (western Alaska), and the Arctic. Southeast Alaska and southcentral Alaska both face the Gulf of Alaska with similar geological features. Western Alaska south of the Bering Strait faces the Bering Sea, and arctic Alaska north of the Bering Strait faces the Chukchi and Beaufort seas of the Arctic Ocean. Gulf of Alaska Coast The Gulf of Alaska coast is a broad region with more coastline than the entire west coast of the contiguous United States. It includes the southeast Alaska panhandle, the northern Gulf of Alaska coast, Prince William Sound, Cook Inlet, the Kodiak Island group, the south coast of the Alaska Peninsula, and the south coast of the Aleutian Islands. All lie along the Pacific Ring of Fire of volcanoes and seismic activity. 17

24 18 Chapter 2 Alaska Coastal Settings Chukchi Sea Barrow Beaufort Sea Kivalina Shishmaref Nome Norton Sound Alaska Bering Sea Cook Inlet Anchorage Bristol Bay Gulf of Alaska Juneau Sitka Ketchikan Canada Figure 2-1. Gulf of Alaska, Bering Sea, and arctic coastal regions of Alaska. Annotated excerpt from NOAA National Ocean Service chart 50; not for navigation. These huge subregions are dominated by mountainous coastlines in a subarctic climate. Mountainous northern coasts such as those on the Gulf of Alaska commonly have three erodible shoreline configurations where human developments are located: alluvial fans, river deltas, and pocket beaches. Alluvial fans, as they often appear in Alaska, are isolated features along steep rocky shores that accumulate from sediment deposited by a mountain stream as it empties into the sea (Figure 2-2). Larger rivers form deltas between mountainsides at the head of fjords along the Gulf of Alaska (Figure 2-3). Pocket beaches in the region usually have a relatively steep slope composed of coarse sand, gravel, or cobbles, as illustrated in Figure 2-4. All three shoreline configurations at some point tend to fall off steeply underwater into deep channels of glacier-carved fjords. These steep submarine slopes of loose material are prone to collapse during severe earthquakes, as occurred in March 1964 at Seward, Whittier, and Valdez. More information on the 1964 earthquake and on earthquake

25 Responses to Coastal Erosion in Alaska in a Changing Climate 19 Figure 2-2. Downtown Seward is located on the alluvial fan of Lowell Creek (left center in photo). The outskirts of Seward to the north lie on the delta of the Resurrection River, whose channel is visible in the upper third of the photo. Provided by City of Seward. Figure 2-3. River delta at the head of Taku Inlet near Juneau, Alaska. U.S. Army Corps of Engineers photo, mil/sites/dvl/default.aspx.

26 20 Chapter 2 Alaska Coastal Settings Figure 2-4. Cobble-covered pocket beach in Kenai Fjords National Park, southcentral Alaska. Orson Smith photo. Yakutat Glacier Bay National Park Juneau Canada Sitka Gulf of Alaska Ketchikan Figure 2-5. Southeast Alaska. Inset shows mountains that dominate the coast, in shades of brown. The narrow continental shelf is light blue. Annotated excerpt from NOAA National Ocean Service chart 16016; not for navigation. Inset from NOAA digital terrain.

27 Responses to Coastal Erosion in Alaska in a Changing Climate 21 hazards in Alaska is available at the Earthquake Hazards Program website of the U.S. Geological Survey: Southeast Alaska Southeast Alaska is a mountainous region of islands, fjords, and rocky promontories (Figure 2-5). The Alaska Coastal Range lines the mainland shore (Figure 2-6). The islands of the Alexander Archipelago immediately to the west are a partially submerged extension of these mountains along the eastern boundary of the Gulf of Alaska. The region has a temperate marine climate with cool, rainy summers and winters with mixed rain and snow. Aerial views of southeast and southcentral Alaska shorelines are available at ShoreZone/viewer.htm. Southeast Alaska has a sharply irregular shoreline, shaped by glaciers whose receding remnants appear among the higher peaks. Valley bottoms and the seafloor are typically covered with unconsolidated glacial and marine sediments. The coast near Yakutat has long sandy reaches atypical of archipelago shores to the south. The entire southeast Alaska region is seismically active, with coastal hazards including earthquakes, earthquake-induced landslides, snow avalanches, and tsunamis. Earthquakes can trigger landslides on steep mountain slopes, which in turn can generate tsunamis on impact with coastal waters. Tsunamis can also be generated by underwater tectonic displacements Figure 2-6. Beartrack Mountain, Glacier Bay National Park, northwest of Juneau in southeast Alaska. National Park Service photo.

28 22 Chapter 2 Alaska Coastal Settings during earthquakes. Information on tsunamis is available at the website of the Pacific Tsunami Warning Center ( ptwc/) and at the Tsunami Information website of the National Weather Service ( Southeast Alaska tide ranges vary from 10 to 17 feet and tidal currents in narrow passages can exceed 5 knots. Though a significant portion of the coast is exposed to the open Gulf of Alaska, most southeast Alaska communities have natural shelter and are subject to waves generated within the confines of archipelago passages. High winds funneled through narrow mountainous channels can still generate erosive wave energy in relatively short and laterally constrained fetches in fjords and between islands. Since most of the region was covered with ice age glaciers around 10,000 years ago, recent on the geological time scale, the coastline is still moving upward in isostatic rebound. This rise of the land out of the sea is happening faster than the sea is rising, so the coast of southeast Alaska is in little danger of inundation by sea level rise. Figure 2-7 is based on measurements by the National Oceanic and Atmospheric Administration (NOAA) that account for both sea level rise and isostatic rebound. The trend shows that water levels are steadily falling at Juneau. Coastal erosion assessments and designs of coastal works in this region should account for both factors affecting long-term water levels. More information on climate change impacts in coastal zones of the United States is available at the Environmental Protection Agency (EPA) Climate Change website ( effects/coastal/) and the Arctic Climate Change Impact Assessment website ( The economy of southeast Alaska has historically relied on the timber industry and timber is readily available as a construction material for shore protection works and other marine facilities. Since bedrock is shallow or exposed in many areas, quarried rock is also available. Quarry development is intensely scrutinized by regulatory agencies and permits to operate commercial quarries are difficult to acquire in Alaska. Though exposed rock is all around, approved quarries are not at hand for every southeast or southcentral Alaska coastal community. Southcentral Alaska The coast of southcentral Alaska has the highest population and the most concentrated development in the state. The area encompasses the thinly populated northern coast of the Gulf of Alaska, Prince William

29 Responses to Coastal Erosion in Alaska in a Changing Climate Data with the average seasonal cycle removed Higher 95% confidence interval Linear mean sea level trend Lower 95% confidence interval Juneau, AK ± 0.43 mm /yr Source: NOAA 0.75 Meters Figure 2-7. The mean sea level at Juneau is falling 4.24 ft per century (12.92 mm per year) based on monthly data. shtml?region=ak. Anchorage Whittier Kenai Prince William Seward Sound Valdez Cordova Homer Yakutat Kodiak Figure 2-8. Southcentral Alaska coast. Inset shows mountains and fjords that dominate the Gulf of Alaska coast and the lower ground along Cook Inlet. Red in the vicinity of Homer (inset) indicates recently available high-density digital elevation data. Annotated excerpt of NOAA National Ocean Service chart 531; not for navigation. Inset from NOAA digital terrain.

30 24 Chapter 2 Alaska Coastal Settings Sound, Cook Inlet, the Kodiak archipelago, and south shores of the Alaska Peninsula (Figure 2-8). Alaska s largest city, Anchorage, is located at the confluence of Turnagain and Knik arms at the head of Cook Inlet. The climate is marine and relatively temperate, similar to southeast Alaska, with a large amount of precipitation from storm and low pressure systems that pass eastward across the Gulf of Alaska. However, more of the precipitation falls as snow in southcentral Alaska than in southeast. Avalanches are prevalent throughout the region. Valdez Whittier Prince William Sound Cordova Gulf of Alaska Figure 2-9. Prince William Sound. Annotated excerpt from NOAA National Ocean Service chart 16700; not for navigation.

31 Responses to Coastal Erosion in Alaska in a Changing Climate 25 Southcentral Alaska shores, except Cook Inlet, resemble shores of southeast Alaska with mountainous fjords as the dominant coastal form. Most coastal developments are located on isolated deltaic plains, alluvial fans, or pocket beaches. Tide ranges vary from about 8 feet along the open coast to 30 feet in Knik Arm at Anchorage. The area is highly susceptible to earthquakes. Unconsolidated sediments of the region, especially on steep slopes, may become unstable during seismic events. The region is susceptible to tsunamis that can sweep in from the gulf. The coast is rising from isostatic rebound. PRINCE WILLIAM SOUND Prince William Sound (Figure 2-9) consists of mountainous islands, narrow passages, and steep fjords along the mainland coast, with the Wrangell Mountains to the east and the Chugach Mountains to the north and west. The entire region was covered with glaciers during the last ice age and the remaining tidewater glaciers attract tour ships to the sound. The largest towns are Cordova, Valdez, and Whittier. Whittier and Valdez are accessible by road, but Cordova can be reached only by air and sea. Both Whittier and Valdez were severely damaged by tsunamis generated by the March 1964 Great Alaska Earthquake (moment magnitude 9.2). Valdez is the site of the terminus and port facility for the Trans-Alaska Oil Pipeline (Figure 2-10). Prince William Sound is the location of the first extensive implementation of the Alaska Ocean Observing System, which provides data from a wide range of useful ocean measurements, including information used for evaluation of coastal erosion concerns. More information about the Alaska Ocean Observing System and its Prince William Sound demonstration project is available at Although protected from the direct onslaught of Gulf of Alaska storms, Prince William Sound is large enough to develop waves dangerous to vessels and to erode shorelines during periods of high winds. Localized extreme high winds can develop through the narrow mountain passes within Prince William Sound and are accelerated through narrow sea passages and fjords. COOK INLET Cook Inlet is bordered by the western shoreline of the Kenai Peninsula and the eastern shoreline of the Alaska mainland north of the Alaska Peninsula, extending 175 miles northeastward from the Gulf of Alaska

32 26 Chapter 2 Alaska Coastal Settings Figure A tanker loads crude oil at the terminus of the Trans-Alaska Pipeline at Valdez in eastern Prince William Sound. Riley Smith photo. (Figure 2-11). The Cook Inlet region contains the largest population density in Alaska, with over half of the state s population residing within commuting range of Anchorage. The western shoreline of the Kenai Peninsula is almost entirely privately owned with development all along the tops of the eroding bluffs that overlook the inlet. The climate along the Cook Inlet coast is in a transition zone between the maritime influence of the Gulf of Alaska and arctic conditions of the Alaska interior. Coastal winds are strongly influenced by the sur-

33 Responses to Coastal Erosion in Alaska in a Changing Climate 27 Susitna River Knik Arm Anchorage North Foreland Turnagain Arm West Foreland Drift River Chisik Island Kalgin Island East Foreland Nikiski Kenai Kenai River Kenai Peninsula Portage Ninilchik Chinitna Point Anchor Point Kachemak Homer Bay Kamishak Bay Augustine Island Flat Islands Seldovia Cape Douglas Barren Islands E Amatuli Island Figure Cook Inlet, Alaska. Annotated excerpts from NOAA National Ocean Service charts and 16660; not for navigation. rounding high mountains. Summers are cool with rain becoming more prevalent toward the end of summer. Winters can be severely cold, but not nearly as cold as the Alaska interior. Precipitation in winter falls mostly as snow, but above-freezing temperatures and rain intermittently occur in winter. The Cook Inlet coastal zone consists primarily of layers of unconsolidated glacial and marine deposits. Glacial deposits along the shore of the upper inlet lie over a layer of clay, known as the Bootlegger Cove formation, which was formed when a natural dam across Cook Inlet blocked downstream flow from ice-age glaciers. The Bootlegger Cove layer was the slip surface for major landslides that occurred in Anchorage and the vicinity during the 1964 Great Alaska Earthquake.

34 28 Chapter 2 Alaska Coastal Settings Figure Steep bluffs of loose glacially deposited material, over 100 ft high, line much of Cook Inlet. Phil North photo. Figure Broad tidal flats lie seaward of the toe of bluffs along Cook Inlet. Coarser sand and gravel tend to remain high in the profile with finer sand and silt collecting near the low tide line. Boulders along the shore, seen in photo, are signs of a prior location of the bluff face. Orson Smith photo.

35 Responses to Coastal Erosion in Alaska in a Changing Climate 29 Furthermore, alluvial deposits that lie over the Bootlegger Cove formation are susceptible to liquefaction during a seismic event. Liquefaction is the conversion of water-saturated unconsolidated sediments into a liquid suspension. Liquefied soil loses its strength and cannot support buildings or stand at steep slope angles that were stable prior to liquefaction. Unconsolidated granular soils are most susceptible to liquefaction, such as beach and stream deposits and recent artificial fills. Liquefaction usually does not occur unless the pores in the soil are filled with groundwater and strong shaking occurs. Information on earthquake and tsunami effects and risks in regions of Alaska is available through the website of the Alaska Earthquake Information Center: The Cook Inlet shore is lined with bluffs of glacial and marine sediments that often exceed 100 feet in height (Figure 2-12). Beaches at the base of these bluffs usually retain the coarser fraction of eroded bluff material along the upper tidal levels. Broad tidal flats of finer sediments form below the mid-tide level (Figure 2-13), except at constrictions where locally accelerated tidal currents sweep away small particles. Tide ranges in Cook Inlet steadily increase northward from 15.6 feet at Homer to over 30 feet in upper Knik Arm north of Anchorage. The region s tides have a diurnal inequality between two high tides and two low tides that occur each lunar day (24 hours 50 minutes). One daily tide range is significantly greater than the other, as illustrated in the Anchorage tide records shown in Figure NOAA/NOS/CO-OPS Preliminary Water Level (NI) vs. Predicted Plot Anchorage, AK from 2008/03/ /03/ Height (Feet relative to MLLW) /07 00:00 03/07 08:00 Predicted WL 03/07 16:00 03/08 00:00 Date/Time (GMT) Observed WL 03/08 08:00 03/08 16:00 (Obs - Pred) 03/09 00:00 Figure NOAA tide records at Anchorage show the diurnal inequality between two successive high tides and accompanying two successive low tides.

36 30 Chapter 2 Alaska Coastal Settings Slope Stability Stability of a soil mass on a slope involves a balance between the force of gravity and resisting internal friction of the soil. When the shear (sliding) stress due to gravity becomes greater than the shear strength (frictional resistance) of the soil, the slope collapses. Shear strength of the soil mass is the internal resistance to sliding along any plane or surface within the mass. Slope failures can occur shortly after a heavy weight is applied or from lesser loads applied over a long period of time. The latter mode of failure, known as creep, is addressed by engineers in terms of reduced shear strength when loads are applied for many hours. The theoretical failure surface is a circular arc or slip circle within the soil mass, as illustrated in Figure Evaluation of slope failure and landslide risk is a complicated task. A licensed engineer specializing in geotechnical analyses should be consulted. Factors that will increase the shear stress and risk of failure include: 1. Placement of loads on the top, such as heavy equipment, buildings, or fill. 2. Excavation of the soil near the bottom. 3. Earthquakes. Slope before failure Slope after failure Gully Slip circle Figure Diagram of slip circle slope failure.

37 Responses to Coastal Erosion in Alaska in a Changing Climate 31 Factors that decrease soil shear strength, therefore increasing risk of failure, include: 1. An increase in water pressure between the soil grains (also known as pore pressure), which may arise from concentrated drainage over the ground or within the soil. 2. Vibrations from nearby heavy equipment operation or from an earthquake. 3. Debris buried within the slope whose adhesion with soil particles is less than that of the soil particles themselves. Coastal slopes tend to suffer from all of these factors leading to slope failure. In cold regions, freeze-thaw effects can further destabilize the soil. Prevention and stabilizing measures include: 1. Redirecting surface runoff and groundwater flow away from the slope. 2. Removing weight near the top of the slope. 3. Reshaping the slope to a flatter grade. 4. Planting the slope with vegetation that forms a root mass with increased shear strength and resistance to surface erosion by wind and runoff. 5. Keeping pedestrian and vehicle (e.g., four-wheeler and snowmachine) traffic off the slope. 6. Building retaining structures and wave protection at the toe of the bluff. More information on landslide risks and slope stability is available from the Landslides Hazard Program of the U.S. Geological Survey: landslides.usgs.gov/ and from the Federal Emergency Management Agency (FEMA) Landslide and Debris Flow (Mudslide) website: gov/hazard/landslide/. See Terzaghi et al. (1996) and Duncan et al. (2005) for more technical information on slope stability analyses.

38 ¹Alaska Earthquake Information Center, University of Alaska, Fairbanks, AK, USA ²Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK, USA ³Pacific Marine Environmental Laboratory, National Oceanic & Atmospheric Admin., Seattle, WA, USA Anchorage ( MAP AREA APPROXIMATE MEAN DECLINATION, 2005 Orthophoto map base by AeroMap U.S., acquired August 10, U.S. Stateplane Coordinate System (1927), Alaska Zone 4. Alaska Department of Natural Resources Division of Geological & Geophysical Surveys This project was supported by the National Oceanic and Atmospheric Administration, National Tsunami Hazard Mitigation Program, through grant NA17RJ1224. Copies of this publication may be obtained from: Alaska Division of Geological & Geophysical Surveys 3354 College Road Fairbanks, AK (phone) (fax) dggspubs@dnr.state.ak.us ( ) The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential or other damages suffered by the user or any other person or entity whether from use of the electronic services or products, any failure thereof or otherwise, and in no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product. This map is intended for emergency management use only. It is not appropriate for use in land-use regulation. See text for discussion of uncertainties. 32 Chapter 2 Alaska Coastal Settings TSUNAMI HAZARD MAP OF HOMER, ALASKA By E.N. Suleimani¹, R.A. Combellick², D.A. Marriott¹, R.A. Hansen¹, A.J. Venturato³, and J.C. Newman³ 2005 ALASKA C o o k I n l e t Kenai Kenai Kenai Kenai Kenai Kenai Kenai Kenai Kenai Peninsula Peninsula Peninsula Peninsula Peninsula Peninsula Peninsula Peninsula Peninsula TRUE NORTH 19º MAGNETIC NORTH SCALE 1:12, KILOMETERS 1 2 METERS MILES FEET EXPLANATION Hachured line indicates maximum estimated tsunami inundation based on all scenarios depicted on Sheet 1. Hachures are on water side of line. Figure Map showing risk of tsunami inundation at Homer, Alaska. White line indicates maximum estimated tsunami inundation. Suleimani et al m High tide with storm surge and storm waves 6 7 m Tidal and river currents dominate nearshore sediment transport Wind-induced sediment transport on beach and bluffs Spring high tide Spring low tide Lower beach (100:1) medium-fine sand and silt Wave, tidal, and river currents induce sediment transport Initial storm erosion Coastal bluffs (1:1 or steeper) Slope failure Storm runoff Imbedded boulder Upper beach (10:1) coarse sand, gravel, and shingles Figure Diagram of processes affecting Cook Inlet bluff erosion.

39 Responses to Coastal Erosion in Alaska in a Changing Climate 33 While the entire Cook Inlet region is seismically active, tsunami risks vary from high in lower Cook Inlet to low in upper Cook Inlet at Anchorage. Homer and its popular Homer Spit are especially susceptible to tsunami inundation. Tsunami risks have been mapped at Homer by the Alaska Division of Geological and Geophysical Surveys (Figure 2-16). All Cook Inlet bluffs are actively eroding from a variety of causes. The exposed faces of the bluffs are often only marginally stable and even slight disturbances can cause a landslide. Wind, rain, and concentrations of runoff over the ground or groundwater can induce erosion of the bluff face. Heavy winter snow can increase spring runoff that contributes to bluff erosion. Pedestrian or vehicle traffic on the face of a bluff is destructive to its stability. The most catastrophic bluff erosion along Cook Inlet occurs when strong onshore winds, and wave and wind-induced storm surges, are superimposed on a high astronomical tide, as illustrated in Figure Bluff material at the toe loses strength when wetted by wave or wave runup and a cavity forms. This weakness leads to a major collapse of bluff material above the cavity and formation of a large gully indenting the bluff face. Adjacent gullies tend to merge, resulting in a retreat of the bluff along hundreds of feet of coast. Building near Cook Inlet bluffs, either by their toe or by their crests, involves a risk of property loss to coastal erosion. Cook Inlet is the only water body along the Gulf of Alaska coast with regularly occurring sea ice. During cold winters, sea ice in northern Cook Inlet can form as early as November and last until April. Figure 2-18 shows historic average conditions of the last half of February (from Mulherin et al. 2001), when ice typically extends farthest south in Cook Inlet. Cook Inlet ice, with rare exceptions, does not exert erosive forces on the shoreline. The presence of ice on inlet water dampens wave generation by wind. Ice frozen to the shore armors against the erosive force of waves; however, when waves do occur, some sediment is moved when large pieces of ice float free on extreme high tides. For reports on sea ice conditions on Cook Inlet and other regions of Alaska, visit the National Weather Service Alaska Region Ice Desk website at arh.noaa.gov/ice.php or the Alaska Ocean Observing System website at KODIAK ARCHIPELAGO AND ALASKA PENINSULA The Kodiak archipelago consists of seven major islands and many smaller ones (Figure 2-8). Shelikof Strait separates the Kodiak archipelago from the mainland Alaska Peninsula. As with southeast and much of

40 34 Chapter 2 Alaska Coastal Settings southcentral Alaska, this region is marked by glacier-carved fjords with rocky headlands and unconsolidated glacial and marine sediments at the heads of the fjords. The climate is similar to southeast Alaska with precipitation falling as rain most of the year. Heavy snowfalls and avalanches occur at higher elevations. Along the coastline, isolated alluvial fans and pocket beaches extend to tidewater. Volcanic activity from the Alaska and Aleutian mountain ranges to the west has deposited layers of volcanic ash within the soil. These layers are slip-prone planes that can be the origin of coastal landslides /29 February Mean Ice Conditions Anchorage Kalgin Island Kenai Fire Island Chisik Island Ninilchik Homer N Augustine Island Kilometers Scale: 1:2,200,000 Projection: Mercator Latitude of true scale: 60 Deg. N Ice concentration in 1/10s surface coverage Stage of development Ice Free New ice ( 0 10 cm ) Young ice ( cm ) New ice (> 30 cm ) New ice ( cm ) Figure Average ice conditions in Cook Inlet during the latter half of February, based on records. While climate change may have since moderated winter ice, severe conditions can still occur. Mulherin et al

41 Responses to Coastal Erosion in Alaska in a Changing Climate 35 The southern and eastern shores of the Kodiak islands and Alaska Peninsula are fully exposed to Gulf of Alaska storms. The few coastal communities in the area are located in naturally sheltered areas, but are still subject to high storm waves during extreme conditions. Strong tidal currents that occur in passages create exceptionally dangerous sea conditions for mariners when wind and current flow in opposite directions. Shelikof Strait is notorious for steep high waves when tidal currents oppose strong winds. Aleutian Islands Characteristics of the north Gulf of Alaska coast, Kodiak archipelago, and Alaska Peninsula apply to the isolated Aleutian Islands to the west. These islands include a number of active volcanoes, which have resulted in rubble slopes of recent volcanic origin and volcanic ash deposits alongside tall rocky cliffs, alluvial fans, and pocket beaches. No major rivers exist, so deltaic plains at the heads of fjords are not typical here. The islands are sparsely populated. Although some natural erosion occurs along the coastline, infrastructure is rarely affected. Western Alaska Western Alaska, as defined here, encompasses the Bering Sea coast of Alaska, including Bristol Bay and Norton Sound, from the north coasts of the Aleutian Islands and Alaska Peninsula to the Bering Strait (Figure 2-19). The Bering Sea is a large, relatively shallow water body that stretches to the eastern coast of Russia. Much of the Bering Sea lies over the continental shelf of western Alaska and depths reach only a few hundred feet for tens of miles offshore. The Bering Sea is the birthplace of intense storms with hurricane-force winds that affect weather across the state and into Canada. Most of the western Alaska coastline is uninhabited. Villages situated along the coast have small populations and are spread far apart. There are no roads in the area that connect to the rest of the state. The larger coastal communities of western Alaska include Dillingham, located on Bristol Bay, and Nome, located on the south coast of the Seward Peninsula southwest of the Bering Strait. Bethel, a marine and aviation transportation hub for Yukon-Kuskokwim communities, is located 40 miles from the coast on the Kuskokwim River. Although Bethel is not subject to the intensity of coastal storms, it does

42 36 Chapter 2 Alaska Coastal Settings Bering Strait Nome Bethel Dillingham Unalaska Gulf of Alaska Figure Bering Sea coast of western Alaska. The delta of the Yukon and Kuskokwim rivers surrounding Bethel is low-lying. Annotated excerpt from NOAA National Ocean Service chart 16006; not for navigation.

43 Responses to Coastal Erosion in Alaska in a Changing Climate 37 experience river erosion on the tidally influenced lower Kuskokwim River. Unalaska is the largest community in the Aleutian Islands, where the Port of Dutch Harbor provides critical services to Bering Sea fishing fleets. Coastal characteristics vary across this vast region to include nearly all types found elsewhere in Alaska. The Aleutian Islands have fjords and sea cliffs and Bristol Bay is lined with bluffs similar in character to those of Cook Inlet (Figure 2-20). The Kuskokwim and Yukon river deltas are characterized by low-lying coastal plains bounded by low rolling hills (Figure 2-21). In some areas of western Alaska, such as the Norton Sound coast near Nome, long reaches of sandy beaches on a sunny summer day resemble contiguous U.S. vacation beaches. Tidal ranges vary from 30-foot extremes in upper Bristol Bay to less than 1 foot at Nome. Figure Coastal bluffs and upper beach near Dillingham, Alaska. Orson Smith photo. Figure Sand dunes are backed by a broad tundra coastal plain with hills in the distance, near Hooper Bay on the Bering Sea coast, Alaska Department of Commerce, Community, and Economic Development, James Hoelscher photo.

44 38 Chapter 2 Alaska Coastal Settings Figure Storm waves wash debris past waterfront buildings onto the streets of Nome, October Alaska Department of Commerce, Community, and Economic Development, Dennis Harvey photo. The shores of western Alaska are frequently inundated by storm surges from Bering Sea storms (Figure 2-22), predominantly during the fall and early winter. The climate is maritime continental with cool, rainy summers influenced by the open water of the Bering Sea. Winters are severely cold, resembling those of the interior of the state, since the northern half of the Bering Sea is typically covered with sea ice during winter months. Climatic warming is causing the sea ice cover to form later, to extend less to the south, and to recede sooner in the spring. This trend allows more wave energy to form and strike the coast and cause erosion, especially during the fall storm season. Most areas of western Alaska have experienced accelerated coastal erosion and shoreline retreat in recent years. The subsurface soils in western Alaska are predominantly finegrained marine and alluvial deposits with discontinuous permafrost (permanently frozen soil) distributed across the region. Permafrost composed of fine-grained sediment is prone to substantial settlement upon thawing when ice between the soil grains melts and flows away as water. Distribution of permafrost across Alaska, with reference to its ice content, is presented in Figure More information on Alaska permafrost is available on the NOAA Arctic Change website at and the Frozen Ground Data Center of the NOAA National Snow and Ice Data Center at

45 Responses to Coastal Erosion in Alaska in a Changing Climate 39 Extract of circum-arctic map of permafrost and ground ice conditions Kilometers Figure Map of Alaska permafrost grades with a view toward ice content and susceptibility to thaw subsidence and erosion. The most severe conditions are along the arctic coast and in the interior. U.S. Geological Survey and International Permafrost Association, Arctic Alaska Coast The coasts of the Chukchi and Beaufort seas (Figure 2-24) lie almost entirely above the Arctic Circle at N, which passes just south of Kotzebue. Average annual air temperatures are below freezing for most of this region, but temperatures have risen in recent years and signs of permafrost subsidence are beginning to appear. Winter sea ice cover has formed later in recent years, leaving shorelines increasingly exposed to wave attack from fall storms. The villages of Shishmaref and Kivalina on the Chukchi coast have been much in the news for their grave coastal erosion concerns. Emergency shore protection has been constructed, but plans were forming as of this writing to completely relocate both Alaska Native communities.

46 40 Chapter 2 Alaska Coastal Settings ARCTIC OCEAN Barrow Beaufort Sea Chukchi Sea Wainwright Prudhoe Bay Kivalina Kotzebue Bering Strait Shishmaref Figure Map of the arctic Alaska coast, showing the broad plain of the Beaufort Sea coast north of the Brooks Range. Annotated excerpt from NOAA National Ocean Service chart 16003; not for navigation. Information about global warming and its impacts on arctic shores is available at the following websites: U.S. Global Change Research Program, gov/ NOAA Arctic Theme Page, Natural Resources Defense Council, Tide ranges are small across the arctic Alaska coast, typically no more than 2 feet. Wind-induced storm surges cause larger water level changes with storm surges of 3-5 feet occurring every few years. Extreme water levels can reach far inland over the low-lying coastal tundra (Figure 2-25). The frequency of severe storms appears to be increasing with climate change and, with less ice protection, more fall and spring storms generate surges and severe wave conditions that reach the shore. This area is more vulnerable to sea level rise than the rest of Alaska. The concurrent prospect of thaw subsidence, due to thawing of ice-rich permafrost lying beneath much of the shore, makes the arctic coast of Alaska one of the most affected regions of the world with regard to climate change impacts.

47 Responses to Coastal Erosion in Alaska in a Changing Climate 41 Figure The coast of the Chukchi Sea commonly has low-lying plains of permafrost-founded tundra behind salt lagoons, and barrier islands with low dunes of coarse sand and gravel. A variety of hardy plants trap wind-blown sand to build the dunes and hold them in place. The crests of Chukchi Sea islands are rarely more than 10 feet above mean sea level, and lower places are washed over during severe storms. Coastal streams typically drain into lagoons that intermittently connect to the sea at tidal inlets. Orson Smith photos. Figure Delta of the Sagavanirktok River at Prudhoe Bay and low coastal plain beyond. Orson Smith photo.

48 42 Chapter 2 Alaska Coastal Settings Figure A barrier island near Prudhoe Bay on the Beaufort Sea shows a gravelly beach with intermittent ice push berms between larger-scale effects of wave action. Summer ice is common, but in 2011 it provides less protection from waves than it did in prior decades. Orson Smith photo. Broad, low coastal plains are characteristic of Alaska arctic shores (Figures 2-25 and 2-26). Both the Chukchi and Beaufort sea have a series of narrow low-crested sandy barrier islands, with salt lagoons behind (Figure 2-27) at the coastal margins of the plains. Barrier islands of the Beaufort Sea coast, and to a lesser extent the Chukchi coast, have finefeatured spits and artfully curved scallops that are associated with extended protection from waves by sea ice. Sea ice is not a consistent continuous erosive force, but rather tends to push up isolated berms when forced up onto the shore by wind friction. Ice pressure and ice push events are a greater concern for artificially constructed offshore islands and structures. Permafrost, permanently frozen for centuries, extends deep below the surface, even under water, along the arctic coast. Bluffs, some 20 or more feet high (Figure 2-28), tend to form above beaches of gravelly sand along salt lagoon shores or coastal reaches not fronted by barrier

49 Responses to Coastal Erosion in Alaska in a Changing Climate 43 Figure Thermal niches have formed along this bluff near Wainwright, Alaska, leading to collapse of large blocks from the bluff face. The shallow veneer of tundra plant life above the permafrost is apparent in this picture. Mikal Hendee photo. islands. Permafrost is exposed to sunlight, warmer summer air, rain, and occasionally the sea at the face of the bluff. Contact with seawater at the toe of the bluff forms a thermal niche, whose growth eventually leads to collapse of large blocks from the bluff face. These permafrost blocks quickly melt and the residual fine sediments are rapidly dispersed.

50

51 CHAPTER3 Coastal Erosion Response Options... Whether tis nobler in the mind to suffer The slings and arrows of outrageous fortune, Or to take arms against a sea of troubles, And by opposing end them?... William Shakespeare (from Hamlet s soliloquy) Coastal communities and property owners experiencing or anticipating erosion have options that range from living with erosion to construction of expensive shore protection. Decisive local and regional coastal zone management can prevent erosion-related problems. Artificial beach nourishment appears natural and expands habitat and recreation opportunities, but it is not permanent. Rigid erosion control fortifies the shore, but may irreversibly alter the natural balance of waves, currents, and sediments. Decision-makers weigh the cost of living with erosion against the long-term cost of measures taken and accompanying adverse impacts to coastal equilibrium. Responses Involving No Construction Living with Erosion No action at all is a worthy option in the absence of the following: loss of life, loss of important infrastructure, loss of critical habitat, or loss of irretrievable assets such as unique archaeology. If buildings or other constructed infrastructure are at risk, their removal is necessary to 45

52 46 Chapter 3 Coastal Erosion Response Options allow erosion to follow its natural course. Removal may involve demolition or relocation. Relatively large buildings can be moved substantial distances away from an eroding coast, often at costs significantly less than construction of shore protection. Relocation by the National Park Service of the Cape Hatteras Lighthouse ( historyculture/movingthelighthouse.htm) is an outstanding example of saving a national landmark without long-term disruption of coastal processes. If relocation is not practical, demolition and removal of structures allows natural conditions to prevail. Coastal Zone Management A national program for protection and restoration of coastal areas was established by the Coastal Zone Management Act of The National Coastal Zone Management Program ( noaa.gov/topics/coasts/management/) fosters partnerships between local, state, and federal government, with provisions to accommodate unique coastal settings and challenges. The National Oceanic and Atmospheric Administration (NOAA) Office of Ocean and Coastal Resource Management provides guidance to state coastal zone management programs. The Alaska Department of Natural Resources until 2011 administered the Alaska Coastal Management Program ( noaa.gov/mystate/ak.html) involving 33 coastal districts. Twenty-eight of these districts were developing enforceable policies to address coastal development, erosion, public access, protection of natural resources, and coastal hazards. The Alaska Legislature dissolved the Alaska program in Limiting new developments in coastal areas by community accord reduces ill-conceived shoreline construction. Conscientious community development planning and application of zoning regulations requires quantitative knowledge of erosion rates and related site-specific physical conditions. A baseline map of nearshore topography and bathymetry, existing construction, and important natural habitats is extremely valuable in judging the extent, rate, and measurable impacts of coastal erosion. Also valuable is knowledge of the local wind, wave, and water level characteristics and the nearshore sediment budget (source, sink, and rates). Rational decisions that restrict developments seaward of a setback line are best made on the basis of this information, with a view toward habitat conservation. Studies of climate change impacts may be

53 Responses to Coastal Erosion in Alaska in a Changing Climate 47 needed to assure that setback lines continue to correspond to the limit of erosion over time. According to the NOAA Office of Ocean and Coastal Resource Management ( about two-thirds of coastal states have established lines a specified distance from the shore, seaward of which new development is restricted or prohibited. Alaska is not one of these states and no local Alaska governments have strictly defined setback line ordinances as of this writing. Setback lines are a form of zoning and, as such, are usually controversial. Once established, setback lines are sometimes the subject of litigation. The abundance of setback line rules, regulations, and ordinances around the nation, however, is a testimony to their utility as a coastal zone management tool. North Carolina, for example, has established setback lines based on type and size of structures, along a distance measured landward from the first stable natural vegetation on the shore. North Carolina s Administrative Code for Ocean Hazard Areas also takes into account rates of erosion in terms of shoreline retreat, such as less than 2 ft/yr or greater that 3.5 ft/yr. Existing structures seaward of a setback line are allowed to stay and be used, but in the event of a disaster (like a hurricane), substantial repair or replacement may not be allowed. Some common categories of setback lines are provided by David Kriebel (U.S. Naval Academy): 1. Fixed setbacks: A critical area is defined in Maryland as a 1,000- foot zone back from the shoreline. Developments are regulated within critical areas, to preclude potentially harmful encroachment on the shoreline and to prevent concentrations of rainfall runoff and loss of shoreline vegetation. 2. Long-term erosion setbacks: The erosion setback is set in North Carolina as 60 times the annual shoreline retreat rate at a site. This policy prevents development at the shore in areas with documented rapid erosion rates, but allows development nearer the shore where little or no coastal erosion has historically occurred. 3. Storm-based setbacks: The onshore reach of wave runup and wave-induced erosion from a 100-year hurricane are estimated in Florida to establish the construction control line (CCL). Developments are regulated seaward of the CCL, with stipulations for provisions such as flood proofing and storm resistance design features.

54 48 Chapter 3 Coastal Erosion Response Options A framework for judging proposals for developments, including construction of erosion control, recommended by the Association of State Floodplain Managers (ASFM 2007, favors shoreline projects that create No Adverse Impacts to adjacent coastal properties or to uses of the shoreline. The principles associated with No Adverse Impact include local community and other stakeholder involvement in decision-making. Having absolutely no impact is difficult to achieve in the coastal zone, but mitigation measures are sometimes possible that can correct impacts perceived as adverse and can even create long-term enhancements. Damage Prevention Options Flood Proofing Many buildings and other structures can be constructed to survive extreme high water levels from coastal storm surge with little or no damage (Figure 3-1). The National Flood Insurance Program (NFIP, specifies construction standards that reduce risks of storm damage to coastal buildings. Buildings in designated Coastal High Hazard Areas should be elevated on an open foundation so the lowest horizontal structural members are above the reach of surge and waves from the 100-year return period storm. This measure is meant to reduce probability of storm flooding and associated property damage to less than 1 percent in any year. Owners of lower structures pay higher flood insurance premiums. Flood hazard information for many Alaska communities is available from the U.S. Army Corps of Engineers ( floodplain_index.htm). The NFIP is administered by the Federal Emergency Management Agency (FEMA). The program requires community implementation of a floodplain management program that meets national standards. FEMA offers technical and administrative guidance to local communities that subscribe to the NFIP. Participating communities are required to adopt resolutions or ordinances that regulate new construction in areas designated by FEMA as Special Flood Hazard Areas. FEMA further requires that... a registered engineer or architect must develop or review the structural design, construction specifications, and plans for construction and must certify that the design and methods of construction to be used are in accordance with accepted standards of practice. The Coastal Construction Manual (FEMA 2000) specifies a range of technical stan-

55 Responses to Coastal Erosion in Alaska in a Changing Climate 49 Figure 3-1. A beach house on Lowell Point near Seward, Alaska, is elevated on a piling foundation to avoid damage from extreme high water. The house is also protected by a rock revetment. Moving the house, if ever necessary, would be expensive but achievable by specialists with proper equipment. The space beneath the house is wisely uncluttered. Orson Smith photo. dards for various coastal hazard risk categories. FEMA provides related guidance to coastal property owners in many forms ( gov/rebuild/mat/mat_trans.shtm), stressing the need to understand risks of coastal hazards, including erosion. The Alaska Department of Commerce, Community and Economic Development also provides guidance for communities and property owners participating in the NFIP ( dca/nfip/nfip.htm and AKQG2003_web.pdf). The department s Division of Community and Regional Affairs administers a grant program for assistance to NFIPparticipating communities for developing plans and implementing projects to mitigate risks of flood damage. Not all Alaska coastal communities participate in NFIP at the time of this writing. Coastal or riverside property owners in communities that do not participate in NFIP

56 50 Chapter 3 Coastal Erosion Response Options are not eligible to receive flood insurance and will not have automatic FEMA disaster response when catastrophic flooding occurs. Relocation Physically picking up and moving buildings and structures to safe ground should be considered in many situations where loss to coastal erosion is imminent. Small buildings and some large ones can be relocated and secondary roads are readily rebuilt on safer alignments, often at relatively low cost compared to coastal erosion control works. Other infrastructure such as buried utility lines and paved roads must be demolished and rebuilt with salvaged or new materials at a new site. If no safe ground exists within practical reach or suitable land is not available, relocation is not a viable option. Also, the value of the property should be considered in the cost-benefit analysis in addition to the infrastructure that is in imminent danger. If the infrastructure is relocated, a conservative setback from the shoreline should be considered. Coastal buildings can be constructed on piling or space-frame foundations that allow the buildings to be moved to a new location with relative ease. In many locations in rural Alaska, heavy lifts and moves need to be done in winter when the ground is frozen, well after dangerous fall storms have occurred. Erosion Control Works Actions can be taken to prevent further erosion or slow the erosion rate to an acceptable level. These erosion control works fall into three categories: nonstructural alternatives, structural alternatives, and composite alternatives combining nonstructural and structural components. Nonstructural Alternatives Nonstructural erosion control works include vegetation, slope reduction, infiltration/drainage control, and beach nourishment. Each alternative has pros and cons and the potential benefits from reducing coastal erosion are site-specific. VEGETATION Planting vegetation on eroding slopes can help prevent erosion in areas that are not exposed to the direct onslaught of wave action. The main problem associated with vegetation in Alaska is the short growing season and slow growth of plants. The plant species must be matched with

57 Responses to Coastal Erosion in Alaska in a Changing Climate 51 the climate, soil conditions, and conditions to which the plants will be subjected such as salt spray or brackish water. Vegetation is often used in conjunction with slope reduction. Plants have been used with limited success to control erosion on Alaska stream banks (Karle et al. 2003), but not in coastal settings with direct exposure to saltwater waves. SLOPE REDUCTION Slope reduction improves resistance to the effects of wind, rain, groundwater flow, and earthquakes. As with vegetation, slope reduction by itself will not be effective protection from direct exposure to high water, waves, or currents. Slope reduction can affect a large horizontal footprint when applied to a steep, tall bluff with loss of previously level land at the top of the slope. Material excavated to reduce the slope can sometimes be applied as protective fill at the toe of the slope. Slope reduction is usually accompanied by planting vegetation and often by construction of a revetment or other rigid protection along the toe. INFILTRATION AND DRAINAGE CONTROL Infiltration and drainage control is important to avoid concentrated runoff that can destabilize an earthen slope. Infiltration control prevents water from flowing down through the soil and includes paving, adding fill with impermeable soil (such as compacted clay), and construction of swales (low ridges) or diversion ditches. Drainage control removes or diverts water already present in the soil and includes burial of perforated pipe, excavation of catch basins, placement of permeable drainage blankets, and contour wattling (rows of stakes interwoven with branches or other pliant material). Design of infiltration or drainage control is best done with expert advice. The Washington Department of Ecology has an informative website on drainage control at wa.gov/programs/sea/pubs/95-107/drainage01.html. BEACH NOURISHMENT Beach nourishment (also called beach fill) is the placement of beach material by mechanical or hydraulic means (Figure 3-2). Beach fill can be hauled by truck from an upland source or placed as slurry pumped from an offshore dredging site. Grain sizes of the fill should be matched as closely as possible to the grain size distribution of the natural beach. The objective of beach nourishment is to replenish material that moves due to longshore or offshore sediment transport. Periodic renourishment is required, on a schedule that depends on the fill material, wave

58 52 Chapter 3 Coastal Erosion Response Options Figure 3-2. Beach fill is hauled by truck to a lakeshore park at St. Joseph, Michigan. The sand fill will ultimately cover an existing seawall and group of beach groins that will remain as fallback protection. U.S. Army Corps of Engineers photo. and current characteristics, and frequency and intensity of storms. Beach nourishment is a temporary solution unless there is a long-term commitment to continue supplying material to the site. NOAA has a comprehensive website that describes beach nourishment at Issues regarding beach nourishment in Alaska include the challenge of finding suitable fill material sources near the erosion problem and high cost of mobilizing equipment to coastal sites. Beach fill with material dredged from offshore has been accomplished at Barrow, Alaska, but costs were high and the time window to safely dredge and transport the fill was brief. The project leaders notably had difficulty locating and excavating beach material of sufficient quality and quantity. The Barrow beach nourishment program reduced erosion for a few years, until the operation was discontinued.

59 Responses to Coastal Erosion in Alaska in a Changing Climate 53 Structural Alternatives Structural alternatives for erosion control often involve construction of some relatively rigid linear works along the shore to armor coastal property and to reflect or dissipate wave energy. The most common armoring alternatives are revetments and seawalls. Beach stabilization structures, such as beach groins and offshore breakwaters, retard erosion by capturing sediment moving along the shore. These options can increase the longevity of a beach fill. All structural projects on the coast are costly and alter shore characteristics. They may have detrimental effects on neighboring coastal properties. Design of protective and beach stabilization structures calls for detailed site-specific information and analyses of sediments, water levels, waves, currents, and associated coastal processes. Composites of two or more structure types may be required to sufficiently reduce risks of property damage during extreme storms. Qualified engineers with specialized experience and knowledge should be consulted, following advice of the Coastal Engineering Manual (USACE 2008, usace.army.mil/cem) and other widely accepted technical references. REVETMENTS Revetments are probably the most common structural erosion response around the world (Figure 3-3). A revetment consists of an armor blanket of rock, shaped concrete blocks, or other heavy wave-resistant materials, placed over a filter layer of gravel, fabric, or both, all laid on a graded slope of natural soil. Revetment slope ratios of 1 vertical to 2 or 3 horizontal are most commonly recommended. Revetments dissipate wave energy in turbulence and friction of water flowing through the pores of the outer armor and filtering underlayers. They also reflect some wave energy back to sea. The filter beneath the armor is designed to prevent passage of natural soil grains, keeping beach property in place. The armor layer protects the filter layer from damage by dissipating and reflecting wave energy. A failure of either component will cause failure of the revetment. Special attention to the transitions along the margins of a revetment at the toe, crest, and flanks are also important to its stability and effectiveness. SEAWALLS Although the terms bulkhead and seawall are often used interchangeably, bulkheads specifically describe a civil engineering structure that is a soil retaining wall holding a substantial fill in place on one side.

60 54 Chapter 3 Coastal Erosion Response Options Figure 3-3. A revetment designed by the U.S. Army Corps of Engineers protects a street and buildings at Shishmaref in northwestern Alaska. Mikal Hendee photo. Seawalls are usually rigid vertical or nearly vertical structures facing the sea to protect coastal property from waves and flooding. Seawalls are often constructed as bulkheads with fill on their shoreward side. Seawalls can be constructed from timber planks (Figure 3-4); steel and aluminum sheet piling; poured concrete; stacked bags filled with sand, gravel, or concrete; wire-mesh gabion baskets filled with rocks; interlocking prefabricated concrete blocks; and a variety of synthetic materials. A vertical impermeable seawall reflects almost all wave energy striking its face. This action causes reflected wave energy to combine with incoming wave energy a short distance seaward, which usually exacerbates wave erosion at that location. A significant concern for seawalls is that they usually lead to scouring of beach material immediately seaward of the wall and associated lowering and steepening of the beach profile. The long-term result can be a seawall that projects seaward from eroded property on either side. In this situation, the seawall becomes a barrier to longshore sediment transport, trapping sediment

61 Responses to Coastal Erosion in Alaska in a Changing Climate 55 Figure 3-4. A seawall constructed of timber planks at Homer, Alaska, protects the toe of a bluff behind. The wood planks cover synthetic sheets that would be insufficient strength by themselves. The slope of the bluff has been reduced by grading to a uniform angle and planted with grass. The synthetic material covering the slope in the photo is temporarily in place to allow grass seeds to take root. Orson Smith photo. on one side and accelerating shoreline retreat on the other. These measurable effects are confined to the immediate vicinity of the seawall. More distant effects induced by seawalls are a matter of controversy and continuing discussion among specialists. Seawalls constructed as partially submerged bulkheads are common in port and harbor areas, often serving as wharfs (moorings for ships and boats). BREAKWATERS Breakwaters, when designed as beach stabilization structures for erosion control, are linear structures built parallel to the shoreline near the offshore edge of the surf zone to dissipate wave energy. They can be either fixed to the seafloor or floating. Offshore breakwaters are usually constructed as elongated mounds of layered rock, but they can also be constructed from prefabricated concrete caissons and other concrete devices. Crests of fixed breakwaters may be low or even submerged and still be effective for erosion control. Floating breakwaters are built of buoyant materials such as large foam-filled concrete rectangles, matrixes of used tires tied together,

62 56 Chapter 3 Coastal Erosion Response Options timber rafts, or manufactured composites. Floating breakwaters are reliable in sheltered areas where wave periods are unlikely to exceed 4 seconds. They are particularly beneficial when nearshore slopes are steep and very deep water is close at hand. Floating breakwaters are usually harbor structures and are rarely used as an erosion response. Since breakwaters decrease the amount of wave energy that reaches the shore directly behind them, the longshore transport of material may become interrupted, depriving down-drift beaches of replenishing material. In some cases, the accumulation of sediment directly behind a breakwater will extend from the shore to the structure itself, forming a tombolo (Figure 3-5). BEACH GROINS Beach groins are structures installed perpendicular to the shore extending into the surf zone. Groins have been constructed from quarried rock, prefabricated concrete caissons, synthetic fabric sacks filled with gravel, wire-mesh gabion baskets, steel sheet piling, and timber planks. Groins are primarily intended to trap sediment transported longshore. Figure 3-5. A low-tide tombolo in Resurrection Bay near Lowell Point, Alaska, has formed naturally by reducing incoming wave energy. Orson Smith photo.

63 Responses to Coastal Erosion in Alaska in a Changing Climate 57 Their main disadvantage is that they impede sediment supply to down-drift properties, which can accelerate erosion of the neighboring shoreline. With proper design and an understanding of the effects and limitations of beach groins, they can be used to retard coastal erosion and retain beaches. They can also be used to minimize sedimentation of harbors and navigation channels. Federal Responses Federal efforts to address coastal erosion in rural Alaska have to date been reactive and historically hampered by conventional federal restrictions that require tangible benefits to the national economy to offset project life-cycle costs. Few federal coastal erosion projects have been authorized under these rules to date (see mil/co/coorg/pmis.htm). Benefits associated with road transportation serving the exceptional coastal development of Homer Spit allowed construction of a rock revetment in 1998 after 15 years of study. A regional study by the Corps of Engineers of coastal erosion concerns under the new authority is available at (USACE 2009). The report identifies 25 communities that require immediate action in response to erosion problems. The Corps of Engineers concurrently received special authority and funding to design and construct coastal revetments at Shishmaref (Figure 3-3), Kivalina (Figure 3-6), and Unalakleet. NOAA offices have made efforts to expand the network of coastal monitoring stations, but these efforts have been hampered by budget constraints in recent years. The Alaska Ocean Observing System ( works to guide federal and state agencies toward a more extensive climate-oriented network of observation stations. A much denser network is necessary for more reliable forecasting of coastal disasters, including severe erosion conditions. Alaska shorelines are typically not well surveyed and vertical tidal datums are poorly defined along much of the coast, hampering efforts to monitor shoreline retreat using aerial photography and satellite imagery. NOAA and Department of the Interior agencies all have an interest in improving baseline definition of coastal events. The National Flood Insurance Program is not universally applied across Alaska. Villages of the Bering Sea and arctic coasts typically lack this source of coastal disaster relief and have not benefited from

64 58 Chapter 3 Coastal Erosion Response Options Figure 3-6. A revetment designed by the U.S. Army Corps of Engineers at Kivalina, Alaska, nears completion in July The final shape is on the right; building materials are stockpiled on the left. Orson Smith photo. associated guidance to wisely choose coastal building sites. Many are located on sites readily associated with flooding and erosion, yet the federal and state governments have, over decades, consistently supported growth of these communities on sites poorly suited to present or future populations. State Responses While no state agency has an explicit mission to deal with coastal erosion in Alaska communities, the Alaska Department of Transportation and Public Facilities has been conscientious about erosion protection of roads and runways. Few roads connect the Bering Sea and arctic Alaska communities, but airstrips serving these coastal villages have needed shore protection. The Nome seawall, a rock revetment of conventional design, is a long-lasting project originally built by the Corps of Engineers and extended and maintained by the state along Norton Sound (Figure 3-7). Alaska universities have begun to focus their limited resources on issues of coastal erosion through research efforts of

65 Responses to Coastal Erosion in Alaska in a Changing Climate 59 Figure 3-7. Seawall in Nome, Alaska. Mikal Hendee photo. individual faculty members and through elective courses in graduate education programs (Smith 2006). The Alaska Department of Natural Resources has provided its coastal managers and other specialists with training on coastal processes through the University of Alaska Anchorage and has embarked on coastal hazards mapping with the Division of Geological and Geophysical Surveys. Regional and Local Government Responses Alaska borough and city governments have participated with the state in community master planning under authority of the federal Coastal Zone Management Act of 1972 and Alaska Coastal Management Act of 1977, administered by the Alaska Department of Natural Resources (NOAA 2008). Until it was dissolved in 2011, the Alaska Coastal Management Program was voluntary at the local level, and provided a strong network of involved city planners, local government officials, and others to promote wise coastal land uses. Coastal erosion responses, whether structural or nonstructural, have potential impacts on sustainable coastal development, and therefore

66 60 Chapter 3 Coastal Erosion Response Options are not always addressed in the coastal management plans of Alaska coastal communities. No Adverse Impact by coastal works has been promoted by a number of community planners (ASFM 2007). The tenets of the No Adverse Impact philosophy are gaining some favorable attention from local and regional governments in Alaska, where owners of coastal residences and recreational properties are reaching out for help with chronic coastal erosion losses. Setback lines or similar zoning regulations directly addressing coastal erosion responses remain nonexistent to date, however. Existing regulations have historically been administered in many places on the Alaska coast with weak resolve regarding adverse impacts. Abuses of permit terms and unpermitted coastal construction are still common in Alaska. Actions Needed The needs in Alaska for support of rational lasting responses to coastal erosion are as great as the Alaska shoreline. Until baseline coastal conditions are measured and the climate is adequately monitored, almost all coastal development in the state will come with uncertain risk of erosion. Uncertainties are currently most severe along the arctic coast. Federal government agencies are constrained by limits of authority and state government has to date not taken much responsibility to proactively address erosion concerns. Without established baselines and continuous monitoring, the frustrations of failed shore protection projects and property loss along the Alaska coast are likely to continue at their present extreme rate or even increase as the climate changes around us. Mistakes of the past and lessons learned long ago in the Lower 48 states appear doomed to be repeated indefinitely along Alaska s shores, unless state, regional, and local governments stand forth against unwise and poorly designed coastal development.

67 CHAPTER4 Revetments and Seawalls Revetments Revetments protect the shoreline by providing a means to let water escape from the soil without erosion of soil particles from wave-induced turbulence and hydraulic pressure. A revetment accomplishes these functions by including one or more permeable filter layers that are ballasted against wave damage by layers of outer armor (Figure 4-1). Because the armor is visible, most people conclude that the armor is the entire revetment, perhaps not realizing that the most important feature is the filter beneath. Revetments are used to protect a stream bank or shoreline on its natural grade or protect fill material placed over existing sediments, as shown in the typical revetment cross-section in Figure 4-2. Revetment filters consist of a blanket of gravel of selected size or of permeable synthetic geotextile fabric (Figure 4-2). A blanket of gravel over the geotextile filter is good practice to protect the fabric during armor placement. The purpose of a revetment filter is to prevent migration of fine soil particles into the lake, river, or ocean and to relieve hydrostatic pressures within the soil mass while bearing the weight of the armor. Filter design depends on the particle size of the original soils and the size of the armor units that can withstand erosive forces of extreme waves and currents at the site. An ineffective filter will result in collapse of the revetment into voids left by loss of soil. A fully effective filter allows water to pass through while retaining soil particles. Armor layers that hold the revetment filter in place can consist of quarried rock (often called riprap); precast concrete blocks; interlock- 61

68 62 Chapter 4 Revetments and Seawalls Figure 4-1. A coastal revetment protects a public park on the island of Maui, Hawaii. Orson Smith photo. Wave runup Primary armor Crest Splash apron Toe Fill Secondary armor Natural grade Geotextile filter Figure 4-2. Typical revetment cross-section with geotextile filter.

69 Responses to Coastal Erosion in Alaska in a Changing Climate 63 ing mats of precast concrete blocks; geotextile bags filled with rocks, gravel, or sand; wire-mesh baskets (called gabions) filled with rock; or variations of these. All revetment armor alternatives are intended to withstand turbulent forces of waves in a severe storm. All rocks or precast concrete blocks in revetment armor layers must be of sufficient size that they won t be moved by breaking waves. High waves will scatter undersized armor units and continue to scour away the filter and soil beneath. Interlocking angular armor units or concrete units tied together with cables reduces the size of individual armor units required for structural integrity of the revetment armor layer. Revetment armor layers must remain permeable for proper function of the filter beneath. Some interlocking systems have such low permeability that high hydrostatic pressures from behind can cause deformation or failure. Filling voids between revetment armor units with grout or soil decreases permeability and increases reflection of wave energy. Careful design is important at places where the revetment structure is vulnerable to undermining at the toe (bottom of slope), crest, or flanks (sides). Special attention to scour protection at the revetment toe is usually necessary. The revetment crest may on occasion be overtopped by extreme wave runup, so the ground immediately behind the crest should be protected by a splash apron of gravel or other permeable cover. Some revetments incorporate elaborate features for drainage of high-volume runoff that may accumulate at the crest during periods of intense rain. Figure 4-3 illustrates the five most common modes of revetment failure due to inadequate armor, scour at the revetment margins, or ineffective filter construction. Table 4-1 presents a checklist for design of coastal revetments that follows guidelines of Design of Coastal Revetments, Seawalls, and Bulkheads (USACE 1995). Further technical guidance is available in the Coastal Engineering Manual (USACE 2008), as well as the Federal Highway Administration s Design of Riprap Revetment (Brown and Clyde 1989) and Tidal Hydrology, Hydraulics, and Scour at Bridges (Zevenbergen et al. 2004). Reliable revetment designs are best accomplished by a licensed engineer with substantial education and experience in coastal designs. Riprap Revetments Rock revetments have two or more armor layers of quarried stones selected to be large enough to remain stationary in specified severe wave conditions. The term riprap is commonly used to describe rocks

70 64 Chapter 4 Revetments and Seawalls Armor displacement Flanking Overtopping Toe scour Ineffective filter Figure 4-3. Five most common modes of revetment failure. The effect on the revetment as constructed (left) is indicated by missing sections or shading at right. placed on a slope for this purpose. ASTM International (2008) defines riprap as rock generally less than 2 tons, specially selected and graded. Riprap may be further characterized as armor rock specified to include a wider range of sizes (i.e., more widely graded) than other rock structures, such as harbor breakwaters where larger, more uniform armor rock sizes are required. Rock for revetments may be specified, for example, to allow the outer armor layer units to weigh up to 25 percent more or less than the median weight chosen for wave stability, with half weighing more than the median. Riprap, thus defined, is used where wave heights are less than 5 ft high. Gradation and other revetment armor rock specifications of the Federal Highway Administration and ASTM are detailed and explicit. FHWA guidance is available at ASTM guidance is available at technical libraries and by subscription.

71 Responses to Coastal Erosion in Alaska in a Changing Climate 65 Table 4-1. Coastal revetment design checklist. 1. Determine the water level range for the site (tides and storm surge). a. Consider both extreme high and extreme low levels. 2. Determine the wave climate for the site. a. Consider 50-year to 100-year return period for armor design. b. Choice of a less severe condition increases risk of future damage. 3. Determine the characteristics of the shoreline sediments, as they vary from upland to beyond the surf zone, and as they vary vertically from the surface downward. a. Variation in sediment characteristics below the surface can reveal recent seasonal or multiyear cycles of change. 4. Identify an optimum armor configuration to resist the design wave conditions. 5. Determine the potential wave runup height to select the crest elevation and associated volume of wave overtopping. 6. Consider local surface runoff and runoff from wave overtopping and include provisions for other drainage facilities such as culverts and ditches. 7. Consider end conditions to avoid failure due to flanking. 8. Design the toe protection. 9. Design the filter. 10. Assure fill material is firmly compacted. 11. Consider environmental impacts of a. Materials supply (e.g., quarry and borrow pit operations). b. Effects on shoreline habitat and migrating species. c. Changes of sediment supply to neighboring property that may be induced by revetment construction. Armor stones are preferably placed individually on the slope to maximize interlocking and to meet an exact geometric design. ASTM (2003) specifies standard sizes of riprap for erosion control and ASTM (2008) provides guidance for material selection and placement. Revetment material selection, design, and construction are more complex than dumping a bunch of rocks on a slope. An advantage of rock revetments is their ability to withstand minor settlement and damage and still function as an erosion control measure. Wave energy is dissipated on the rough, porous revetment surface, so

72 66 Chapter 4 Revetments and Seawalls wave reflection is minimized and runup is not as high as on smoother slope protection. A rock revetment is a proven method of shore protection, but good rock and heavy construction equipment to properly build a revetment in severe conditions can be expensive. The trade-off between smaller rocks on a flatter, wider revetment with larger rocks on a steeper, narrower slope involves economic and environmental considerations. Revetment material quantities are minimized with a steeper slope, but steep slopes require larger, more expensive armor units. Steeper slopes reduce the revetment horizontal footprint, which may affect real estate or right-of-way transactions and mean less habitat impact. For resistance to earthquakes and general stability considerations, revetment slopes are usually not less than 1 vertical to 2 horizontal (1v:2h) and should never be steeper than 1v:1.5h. In areas where ice may impact the revetment, a slope of 1v:3h or flatter is preferred, based on laboratory experiments at the Cold Regions Research and Engineering Laboratory (Sodhi et al. 1996). The natural ground may require excavation or fill to provide a regular slope on which to build a revetment. Fill should be free of large rocks and debris and properly compacted. In Alaska, surprisingly few operating quarries can supply an adequate quantity of armor stone suitable for riprap revetments. Many Alaska projects require transportation of armor rock over long distances, by truck for projects along the road system or by barge to the many coastal settlements without road access. In permafrost areas, the underlying frozen soils should be assessed to determine if future thawing will cause unacceptable settlement. It may be necessary to pre-thaw the permafrost and compact the unfrozen soils prior to construction of the revetment. It is possible to place insulation or passive cooling systems beneath a revetment to keep the foundation frozen, but this strategy may not be effective for a long period in a warming climate. Pre-cast Concrete Revetment Armor Concrete blocks molded into complex shapes, some patented, are available for revetment armor where equivalent rock sizes are more expensive to import. Precast concrete dolosse shown in Figure 4-4 are examples of commercially available options. These shaped blocks are cast in special molds, sometimes with added noncorrosive fiber reinforcement. Larger blocks may be formed and poured at the construction site, but more often are cast elsewhere and brought to the site by barge.

73 Responses to Coastal Erosion in Alaska in a Changing Climate 67 Figure 4-4. A revetment slope armored by precast concrete dolosse (left side of photo) is topped by a rock splash apron, at the airport in Unalaska, Alaska. Harvey Smith photo. Shaped concrete blocks placed as individual units on a revetment slope are designed to interlock more efficiently than angular rock and thus require less weight. Patent costs, import of cement and molds, and quality control in casting often result in higher costs than transport of suitable rock over surprisingly great distances to Alaska coastal sites. Once broken, shaped concrete blocks are less effective than rock of the same size. Revetment repairs with molded concrete units are typically more difficult and expensive than with rock. For these reasons, open coast revetment construction with quarried rock armor has the most experience and best record in Alaska. Marine Mattresses Concrete units that are structurally connected to one another form a revetment that distributes stresses. The interlocking mechanism and connections between units have to be strong to resist both uplift and down-slope forces. One advantage of this mattress approach is that the individual armor units of the interlocking structure don t have to be as large for stability as those used individually. Another advantage is that a substantial portion of the revetment armor can be assembled off-site with improved quality control and then rapidly placed (usually by crane lift) in large, uniform sections. This approach to revetment

74 68 Chapter 4 Revetments and Seawalls Figure 4-5. Marine mattresses on a revetment at Cape May, New Jersey. U.S. Army Corps of Engineers photo. armor is recommended only for low to moderate wave exposure (Hughes 2006). Mattress designs involving synthetic mesh containers of small rocks, as shown in Figure 4-5, have not been tested in Alaska freezethaw and sea ice exposure conditions. Low-Cost and Emergency Options Low-cost erosion control measures inevitably come with a high risk of failure. Cost constraints pressure property owners and local governments to accept affordable and expedient shore protection concepts promoted by enthusiastic entrepreneurs. Many of these methods have little chance of lasting long in an exposed coastal environment. Fabric cases filled with sand and gravel or wire-mesh gabion baskets filled with cobbles or sandbags may, in good conditions, prevent erosion until a more durable structure can be constructed. They cannot withstand the direct force of ocean waves for long, which has been proven many times all along the Alaska coast (Figures 4-6 and 4-7). Sunlight degrades the strength of the fabric, and freeze-thaw effects and sea or river ice forces cause deterioration. Fabric or wire-mesh structures are not durable enough to withstand impacts from floating logs or fourwheeler vehicle traffic. Agencies and construction material vendors continue to search for affordable, transportable revetment armor and other

75 Responses to Coastal Erosion in Alaska in a Changing Climate 69 Figure 4-6. Failed wire-mesh gabion baskets at Shishmaref, Alaska. Geotextile that lined the rock-filled gabions is intertwined with the rocks and wire. Mikal Hendee photo. Figure 4-7. Wire-mesh gabions, gravel-filled fabric tubes, and sandbags in disarray at Shishmaref, Alaska, Mikal Hendee photo.

76 70 Chapter 4 Revetments and Seawalls erosion control components that will withstand destructive energies of the coastal ocean. Arctic and subarctic conditions in Alaska, combined with ocean forces, make only the strongest and more expensive options reliable as long-term responses to coastal erosion. Seawalls Seawall is a term used for coastal works with vertical walls parallel to the shoreline. A seawall may be built in response to coastal erosion or it may be intended as a place for vessels to tie up. Bulkhead and retaining wall are terms for a vertical wall holding an earth fill in place. Steel and aluminum sheet piling, precast panels of concrete, timber, and other materials are used to build retaining walls. Earth fill is held behind the wall against gravity and other forces that would otherwise drag the fill downhill into a more natural slope. A seawall bulkhead Tieback rod Fill Anchor pile Sheet-pile bulkhead Waler Natural grade Figure 4-8. A steel sheet-pile seawall at Dillingham, Alaska, protects the toe of coastal bluffs from erosion. The inset illustrates how the horizontal member (waler) is anchored within the fill to resist outward forces from the weight of soil and water behind the wall, Orson Smith photo.

77 Responses to Coastal Erosion in Alaska in a Changing Climate 71 must withstand the forces of waves and currents on its seaward side. Sea ice forces and freeze-thaw effects in the fill are also destabilizing factors that matter in Alaska. Well-built structures of steel, aluminum, concrete, and wood are capable of withstanding wave, current, and ice forces. Interlocking sheet piling can be driven without anchoring for low seawalls or anchored for higher ones. Anchors can consist of piles driven behind the seawall (Figure 4-8) or of concrete blocks or other heavy, bulky objects known as dead man anchors buried in the fill. Seawall sheet piles must be driven deeply to resist overturning forces, which can be difficult in areas underlain by shallow bedrock or permafrost. Sheet pile must be driven deep enough to allow for prospective scour along the seaward toe. Anchors with cables or rods that tie them to the waler along the seawall face can corrode and dangerously weaken the entire seawall. Corrosion prevention for all corrodible features of a seawall is an important consideration. Abrasion of coatings by wind- and wave-driven beach sediments is inevitable. An alternative to conventionally anchored sheet-pile seawalls is the patented Open Cell (PND Engineers, Inc.) sheet-pile wall, which consists of sheet pile driven in a U shape, as viewed from above. An interconnected series of U shapes results in a seaward face of convex arches (Figure 4-9) that relies on the interlocking of micro-anchors along the tail walls that extend into the fill for stability, instead of a conventional anchoring system. Figure 4-9. Open Cell sheet-pile seawall just after construction at Hawks Beach on the southern Cook Inlet coast of the Kenai Peninsula, Alaska. PND Engineers, Inc. photo with permission.

78 72 Chapter 4 Revetments and Seawalls Construction of a seawall causes localized changes in the beach, but does not necessarily induce large-scale accelerated beach erosion, according to a thorough review of literature and case studies summarized in the Coastal Engineering Manual (USACE 2008, Part V Ch. 3). This finding continues to be debated in technical literature, however. Because seawalls must be nearly impermeable to function as retaining walls, they are efficient reflectors of wave energy. Waves reflected offshore combine with incoming waves to amplify forces on sediments immediately seaward of a seawall. Scour along the toe of a seawall is a typical result of wave reflection. Figure 4-10 shows the usual effect of a seawall on the profile of the beach in front and the bluff behind when larger coastal trends are causing a shoreline retreat. Scour protection can be provided by placing rock along the toe in the manner of a revetment, as in Figure Figure 4-12 illustrates the difficulties of underestimating wave-induced scour at the toe of a seawall. The Dillingham seawall of Figure 4-8 has also suffered up to 6 feet of toe scour. A seawall projecting into the surf zone will act as a barrier to longshore transport of beach sediment. The up-drift side of a barrier that extends into the littoral zone will accumulate beach material. Beach material on the down-drift side will be depleted, due to a deficit of updrift sediment supply caused by the structure. Figure 4-13 illustrates the prospective long-term effect of a seawall protruding into the surf Bluff and beach profile prior to shoreline retreat Shoreline and bluff retreat without the seawall Profile of land behind seawall is retained High tide Low tide Scour at seawall toe Figure Schematic of profile retention behind a seawall as adjacent shoreline continues to retreat. Also illustrated is the toe scour that is typical without construction of scour prevention measures. Seawall scour protection usually consists of a revetment built along the seawall toe.

79 Responses to Coastal Erosion in Alaska in a Changing Climate 73 Gravel Riprap Geotextile fabric Figure Concept design of seawall toe scour protection. Figure Contractors struggle to extend downward the toe of a timber seawall at Homer, Alaska, before it is undermined by wave-induced scour. This is the same seawall shown in Figure 3-4. Orson Smith photo.

80 74 Chapter 4 Revetments and Seawalls Fillet of beach material accumulates on up-drift side of barrier Down-drift scallop forms due to deficit of sediment supply to balance wave-induced longshore sediment transport Prevailing wave direction Figure Concept sketch of long-term effect of a barrier projecting into the surf zone. Figure Gabion seawall at Barrow, Alaska, just after construction in Sand and gravel fill is contained within the wire mesh by geotextile. The structure was subsequently damaged by storm waves. Mikal Hendee photo.

81 Responses to Coastal Erosion in Alaska in a Changing Climate 75 Figure Remains of a failed gabion seawall at Shishmaref, Alaska, Mikal Hendee photo. zone. A seawall isolated in the middle of a beach experiencing largescale erosion can be expected to eventually form a prominence as the adjacent shoreline retreats. As this situation develops, the sidewalls of the structure perpendicular to the shoreline become increasingly important for retaining the fill behind the seawall. As with revetments, expedient low-cost options exist for seawalls. These also are often less durable and have more risk of early failure than more conventional designs. Wire-mesh gabions filled with stone, gravel, or sand have been used to construct bulkheads with limited success throughout Alaska (Figure 4-14). Most of these structures hold up for a few seasons or less before they are destroyed by storm waves (Figure 4-15). Only the strongest, most durable materials and designs are likely to last for a decade or more in the Alaska coastal environment.

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83 CHAPTER5 Beach Nourishment and Beach Groins Beach Nourishment Purposes and History Beach nourishment, sometimes also called beach fill, is a response to coastal erosion that has increasingly become the first choice of coastal communities in the contiguous United States. Beach nourishment involves placing large quantities of sediment along the eroding shoreline (Figure 5-1), directly addressing sediment deficits by in-kind Figure 5-1. Beach nourishment at Indiana Dunes National Lakeshore. U.S. Army Corps of Engineers photo. 77

84 78 Chapter 5 Beach Nourishment and Beach Groins replacement. Shoreline processes causing erosion are affected in a positive way by the presence of the fill material. Waves break farther offshore, reducing or eliminating inundation of valued shoreline property. The fill material, if similar to natural beach sediment at the site, will respond in a like manner and in time also will be taken away by wave action. The fill is sacrificial with a finite lifetime before renourishment is necessary (NOAA 2007). Risks for property damage increase when periodic renourishment or post-storm repairs are not performed as needed. Since beach nourishment is sacrificial in nature, public misconceptions about the periodic need for renourishment sometimes lead to controversy (NRC 1995). Fill material that closely resembles native beach material will best maintain shoreline habitats and aesthetic values (Figure 5-2). A major challenge in planning a beach nourishment project is location of a source of fill material similar in character to native beach material. Considerations for fill material excavation and transport are often as crucial, particularly in the permitting process, as for placement of fill on an eroding beach. Composite coastal erosion responses incorporating fixed structures with seaward beach nourishment can enhance effectiveness while maintaining beach habitat, scenery, and traditional human activities along the shoreline. Structures such as seawalls and revetments, located shoreward of the beach fill, reduce risks to upland property during extreme storm events. Groins and breakwaters also can be incorporated to extend the life of beach nourishment. Small, privately funded, beach nourishment projects began in southern California in the 1930s. Larger federally funded beach nourishment projects were first constructed in the 1960s to mitigate interruption of natural sediment transport patterns by jetties at river entrances and by harbor breakwaters. The Coastal Engineering Manual (USACE 2008) states that the primary function of a federal beach nourishment project is to provide improved protection to upland structures and infrastructure from the effects of storms. Beach nourishment is now recognized as an effective direct response to coastal erosion (Hapke et al. 2006). Very few beach nourishment projects have been undertaken in Alaska. The North Slope Borough sponsored a beach nourishment program in 1995 at Wainwright on the Chukchi Sea coast. Approximately 95,000 cubic yards of fill material dredged from a nearby offshore site were placed on the beach at Wainwright. The dredge was moved to Barrow in 1996 where beach nourishment operations continued through

85 Responses to Coastal Erosion in Alaska in a Changing Climate 79 Figure 5-2. Shore protection at Coney Island, Brooklyn, New York. U.S. Army Corps of Engineers photo. 1999, when the dredge was severely damaged in a storm. Beach nourishment was not resumed at Barrow. On the east coast of Cook Inlet, beach fill was placed in front of a sheet-pile retaining wall constructed at the toe of an eroding bluff just north of the Nikiski ship terminals, in The beach fill addressed changes caused by a series of events. In the late 1960s a large bulkhead was built, known as Rigtenders Dock, which blocked sediment transport by waves from the south (Figure 5-3). An effort to protect the rapidly eroding bluff just north of Rigtenders Dock included construction of a sheet-pile wall that unfortunately accelerated local erosion by reflecting storm waves (Smith et al. 2003). The 2004 beach fill operation partially restored the beach at the sheet-pile wall with material from immediately south of Rigtenders Dock. This effort was apparently successful for

86 80 Chapter 5 Beach Nourishment and Beach Groins Cook Inlet Open-cell sheetpile wall Figure 5-3. Rigtenders Dock at Nikiski, Alaska, prior to 2004 beach nourishment. After 2004, the beach nourishment protected the sheet-pile wall on the dock s north (right) side, where longshore sediment transport is blocked by the dock structure. Photo provided by PND Engineers, Inc. several years in restoring the beach while protecting the adjacent wall and bluff from erosion. Advantages and Disadvantages of Beach Nourishment The National Resource Council (NRC 1990) declared that,... beach nourishment is a viable engineering alternative for shore protection and is the principal technique for beach restoration. Beach nourishment can provide protection from storm waves and flood damage, when: 1. appropriate standards are applied for planning, design, and construction; 2. erosion processes are quantified and effectively incorporated in the design; and 3. beach renourishment is carried out on schedule. ADVANTAGES Beach nourishment provides protection to valuable coastal property from storms and long-term erosion, while providing a wider beach for recreational and subsistence activities. Wider beaches provide additional habitat for coastal flora and fauna. Endangered sea turtles have benefited from wide beaches restored by beach nourishment along the southern U.S. Atlantic coast (Greene 2002). Beach nourishment is sometimes accomplished through beneficial use of dredged material excavated from harbors and channels for the sake of navigation improvement. A compelling advantage of beach nourishment is its natural appearance and response to shoreline processes. Changes wrought by a

87 Responses to Coastal Erosion in Alaska in a Changing Climate 81 well-designed beach nourishment project are more on the order of restoration to a previous natural state than of unnatural alteration of the coastal environment. Beach nourishment has a limited life, usually only a few years, before the fill material has been sacrificed to wave action, so any unintended impacts have limited duration. DISADVANTAGES Beach nourishment is most effective when accomplished on a relatively large scale (NRC 1995). A fill of only a few hundred feet along the beach within the bounds of one or two waterfront lots may not last long enough to be effective. The fill needs to affect a significant segment of a littoral cell to provide lasting protection from storms, and even then renourishment will be required every few years if the natural beach has suffered long-term erosion. The scale and cost of the most effective beach nourishment projects usually require government sponsorship. Cost overruns have occurred (Pilkey and Dixon 1996). Fill of tidelands requires a U.S. Army Corps of Engineers Section 404 Permit along with scrutiny by state and federal agencies concerned with impacts to flora and fauna and to their natural habitats. These agencies are also concerned with impacts from excavation of fill material from the borrow site. Thorough analysis of potential impacts is necessary to satisfy agency concerns. Proponents and opponents of beach nourishment as a response to coastal erosion continue to debate. During the initial construction of a beach nourishment project, the sediment is usually placed along the shoreline at slopes steeper than equilibrium, as shown in Figure 5-4. The steeper slopes are more practical to place and allow more accurate documentation of the material volume. The sediment thus placed gradually moves seaward under Pre-construction profile Initially-placed trapezoidal berm Adjusted fill profile Figure 5-4. Concept sketch of placed beach nourishment cross-section compared to profile following exposure to tides and waves.

88 82 Chapter 5 Beach Nourishment and Beach Groins the influence of wave action until it reaches an equilibrium profile (NRC 1995). Some critics believe the resulting adjusted fill profile is steeper than the pre-nourished profile. They contend that the steeper profile encourages more rapid erosion, which requires renourishment at ever increasing intervals (Pilkey and Dixon 1996). Beach nourishment projects have the potential to severely impact important cultural resources. Onshore or offshore borrow excavations can damage or destroy archaeological sites, such as shipwrecks and prehistoric locations of interest. Coordination with state historic preservation officials is necessary for compliance with the National Historic Preservation Act of The biological impacts that beach nourishment projects may have on flora and fauna include diminished reproductive success, reduction in biomass of prey food items, and long-term changes at sites where fill material is excavated. The Atlantic States Marine Fisheries Commission is concerned about the effect that offshore dredging for fill material for beach nourishment projects may have on fish habitat (Greene 2002). Some areas may have accumulated contaminants in offshore areas otherwise attractive as borrow sites. Short-term environmental impacts associated with removing material from offshore sources appear to be no worse than natural disruptions caused major storms (NRC 1995). Despite disadvantages, beach nourishment has become the preferred alternative to combat beach erosion in the United States, Australia, and Europe (NRC 1995). Table 5-1 outlines objectives, criteria, and measures for performance of successful beach nourishment projects. Site-specific objectives and criteria for success should be defined by early public interaction of prospective stakeholders in a proposed beach nourishment project. The criteria of Table 5-1 allow objective appraisal of real benefits from proposed beach nourishment projects. Beach Nourishment Design Once beach nourishment is selected as the primary response to coastal erosion, project boundaries and a preliminary configuration must be determined. Quantitative knowledge of the project s physical setting is critical for good design decisions (USACE 2008). Characteristics of the littoral system in which the project lies should be defined early in the design process, including effects of structures already present within the littoral system. A current survey of the beach and nearshore underwater area is important for initial design. The variety of sediments on the beach and beneath the surf zone should be assessed. Determining

89 Responses to Coastal Erosion in Alaska in a Changing Climate 83 Table 5-1. Evaluation of beach nourishment projects (after NRC 1995). Objectives Criteria for success Measures of performance Provide, enhance, or maintain a recreational beach Protect facilities from wave attack Maintain an intact dune or seawall system Create, restore, or maintain beach habitat Protect the environment Avoid long-term ecological changes in affected habitats Acceptable width and capacity during the beachgoing season Sufficient beach material remaining to dissipate wave energy No overtopping during storms that do not exceed design water level and wave height Post-fill erosion rates comparable to historical values Sediment distribution and vegetation above the beach are similar to natural conditions Return to a natural condition within an acceptable time period Periodic beach surveys using quantifiable observation techniques, such as aerial photography Evaluation of structure and flood damage after storms Periodic dune or structure inspections Periodic beach surveys include beach sediment characterization Observations of habitat characteristics and condition Periodic monitoring of resident fauna the frequency and severity of storms at the project site, and the historic variability of erosion caused by storms, may require new measurements to supplement historical data. Borrow sources for beach fill can be divided into four categories: terrestrial, back barrier, offshore, and navigation channels. The most important borrow material characteristic is its distribution of sediment grain sizes. Terrestrial sources near the proposed beach nourishment site may be ancient beaches, coastal inlets, or riverbeds with material very similar to present-day native beach material. Terrestrial sources often have lower excavation, transport, and placement costs, especially if floating equipment is not needed. Offshore sources require use of floating equipment, but may have grain size distributions most similar to native beach material. Given sufficient quantity at an offshore source near the beach nourishment site, hydraulic dredges can efficiently accomplish excavation, transport, and placement in one continuous operation (Figure 5-5). Weather delays are common with use of floating equipment exposed to coastal conditions. Back-barrier sources of fill material include deposits in back-barrier marshes, tidal creeks, bays, estuaries, and lagoons behind barrier

90 84 Chapter 5 Beach Nourishment and Beach Groins Figure 5-5. Beach fill placement by hydraulic dredge. U.S. Army Corps of Engineers photo. islands and spits. These sites are protected from open coast wave action, but may lie in habitats that are sensitive to disturbance. Material from these sources can be too fine-grained for effective beach fill. Coarser, more suitable material may be found in back-barrier deposits associated with active or relic inlets (USACE 2008). Creation and maintenance of navigation channels, ports, and harbors often requires excavation and disposal of large quantities of sediment that may be highly suitable for beach fill. Productive use of dredge material from a navigation project is desirable, since a disposal site for dredged material from navigation projects must always be found. Costs of excavation, transport, and placement may be shared by the two projects, if the material is suitable and increased transport and placement costs don t exceed other options for the beach fill project. Dredged material from higher energy areas, such as rivers and shoals in coastal inlets, is more desirable fill than material from low energy environments, such as protected estuaries and bays. Beach fill is initially placed in a trapezoidal cross-section, which is rapidly modified by contact with tides and waves (Figure 5-4). Fill placement often does not extend beyond the intertidal beach (USACE

91 Responses to Coastal Erosion in Alaska in a Changing Climate ), particularly if placed with conventional mechanical equipment. Hydraulic placement is more accommodating to underwater placement. Following initial adjustment, a minimum beach width is desired for dissipation of wave energy and recreation or subsistence purposes. A berm at the upper limit of the fill may also be constructed for added wave and flooding protection. A portion of the fill material, consisting of grains smaller than those of the native beach material, will soon be lost offshore by a process called winnowing. The Coastal Engineering Manual (USACE 2008) describes a method to calculate an overfill factor to account for this early loss of material, based on comparison of fill and native sediment grain size distributions. The volume of fill initially placed must include an extra amount to account for winnowing. Lateral spreading losses must also be estimated as the rate at which fill material is transported out of the project limits in the longshore direction. Longshore transport, driven by waves intercepting the coast at an angle, is the primary cause of lateral spreading (USACE 2008). Figure 5-6 illustrates lateral spreading of a beach fill project. Coastal structures that exist within the project limits may complicate estimation of lateral spreading rates. Although lateral spreading represents a loss of material to the project area, down-drift beaches may realize benefits. This loss ultimately leads to a need for renourishment, so the rate must be estimated with care and include allowances for uncertainties. More sophisticated approaches to beach fill cross-section design and estimation of renourishment schedules and volumes require numerical modeling of the ambient shoreline processes. As with other constructed coastal erosion responses, the services of a licensed professional engineer with specialized training and experience should be applied to beach nourishment design. Costs to build effective beach nourishment projects typically exceed the budgets of private property owners. The Flood Control Act of 1936 authorized federal cost participation for the restoration and protection of the shoreline of the United States (NRC 1990). Federal policies determine the methodology by which project cost sharing, based on an evaluation of project costs and benefits, is calculated by the Corps of Engineers. Current policy calls for the Corps of Engineers to consider both storm damage reduction and recreation enhancement benefits. Construction of a cost-shared federal project requires, among other things, a determination of federal interest and support by state and local cost-sharing partners. Federal interest usually applies to public

92 86 Chapter 5 Beach Nourishment and Beach Groins Original shoreline Spreading losses View from above (plan view) Nourished shoreline Offshore adjustment of initial placement prism Spreading losses Adjusted profile (course fill material) Initial fill placement Adjusted profile (fine fill material) Figure 5-6. Concept sketch of beach fill initial adjustment and spreading losses. After NOAA and not to private coastal assets. The Alaska state government owns most tidelands, but adjacent private property may not qualify for federal assistance without exception to national policy. Dynamically Stable Beaches Alaska beaches, with sediments of glacial origin, often include a mix of sand and much larger gravel in the range of several inches in diameter. The larger material tends to be segregated by wave action onto the upper beach at and above the normal high tide level. The Alaska climate is not conducive to sunbathing, but beaches are popular for walking, beachcombing, fishing, and as convenient routes for travel by fourwheelers, snowmachines, and other off-road vehicles. These circumstances accommodate an erosion response option that can be viewed as intermediate between beach nourishment and revetment designs. Dynamically stable beaches involve placement of gravel or rocks significantly larger than natural beach material, but significantly smaller than armor units for conventional revetment design. This coarse beach

93 Responses to Coastal Erosion in Alaska in a Changing Climate 87 material is placed in a trapezoidal fill section, as is beach nourishment sand, and the initial geometry is likewise modified by waves to an adjusted shape. The adjusted shape is dynamically stable, and will last far longer without maintenance than beach nourishment. The resulting gravel slope is passable for pedestrians with ordinary Alaska beach-walking footwear. The Alaska Department of Transportation and Public Facilities has constructed several successful dynamically stable beaches for erosion control (Figure 5-7). Findings to date indicate these projects provide protection equivalent to a conventional revetment for substantially less cost. The agency is planning research to improve its beach nourishment and dynamically stable beach designs. Beach nourishment and construction of dynamically stable beaches are effective responses to coastal erosion that take a more natural approach than other constructed alternatives. Careful investigations of potential impacts to local coastal flora and fauna should of course be made. Coastal communities of Alaska should carefully review beach nourishment and dynamically stable beaches as alternatives when considering a long-term commitment to prevent erosion. Terminal beach groin at opening of fish lagoon Dynamically stable beach (fill) Figure 5-7. The dynamically stable beach of 2 to 3 inch cobbles, placed by the Alaska Department of Transportation and Public Facilities in 1999, beside the Nick Dudiak fishing lagoon on Homer Spit. The beach cobbles, in combination with a terminal groin at the lagoon s opening to Kachemak Bay, have kept this reach of the spit shore stable to date without maintenance or adverse impacts. Harvey Smith photo.

94 88 Chapter 5 Beach Nourishment and Beach Groins Beach Groins Beach groins are narrow structures, essentially fences of rock, wood (Figure 5-8), steel, or concrete, built to trap sediment moving along the shore within the littoral zone. They have been used for centuries to stabilize beaches. Beach groins may be built in groups or as solitary structures. Sediment moving along the beach can be retained by impermeable barriers oriented across the beach. Sediment moved along the shore by waves is trapped by a rigid barrier constructed in its path. Structures built perpendicular to the shoreline across all or part of the surf zone will trap sediments on the up-drift side. Sediment accumulates in a similar manner at river mouths or other places where bathymetric features refract incoming waves and disrupt longshore sediment transport capacity. Beach material accumulated on the up-drift side of a groin is reoriented to more directly face the waves, which in this area reduces wave forces moving sediment along the shore (Figure 5-9). When sufficient sediment is trapped to reach around the groin s offshore end, longshore sediment transport begins to bypass the groin at a rate reduced from Figure 5-8. These wooden crib beach groins were built as a low-cost experiment at Ninilchik, Alaska, on Cook Inlet in the late 1970s. The groins stabilized the upper beach for several years, until they were destroyed by winter ice. They were submerged only at high tide and did not affect longshore sediment transport at mid- to low-tide water levels.

95 Responses to Coastal Erosion in Alaska in a Changing Climate 89 that prevailing before groin construction. Sediment can also spill over the top of low-crested groins. Beach groins are typically designed with the objective of keeping a minimum width of dry beach as protection from storm waves. The sand-trapping capacity and bypassing rate of a beach groin are controlled by its length and its height above the beach. Groins built on the upper beach that are submerged only at high tide or during storms only affect sediment transport in those relatively short-duration conditions (Figure 5-8). The most serious negative effect on beaches attributed to groins is the scour that typically occurs on the down-drift side (Figure 5-9). Large-scale longshore sediment transport energy is not much affected by the groin structure itself and resumes its full pre-groin level a short distance down-drift of the groin. Up-drift sediment supply is cut off by the groin, however, and wave energy instead scours sediment from the natural shoreline. The result is exacerbated erosion in the lee or downdrift side of the groin. The crest elevation of groins may be designed for substantial overtopping by sand, so that longshore transport is not completely disrupted by their presence (Aminti et al. 2004). Likewise, groin length and permeability (Poff et al. 2004) can be adjusted to allow some beach sediment to pass to avoid adverse impacts on the down-drift beach (USACE 1992, 2008; Basco and Pope 2004). Methods of modifying old groins or Prevailing wave direction Bypassing Up-drift accumulation Longshore transport energy Down-drift scour Pre-groin shoreline Figure 5-9. Concept sketch of beach groin impact on an otherwise straight stretch of beach.

96 90 Chapter 5 Beach Nourishment and Beach Groins designing new groins to bypass more sediment include opening a gap or reducing the crest height (Donohue et al. 2004). Groin fields are arranged so each groin in the series traps longshore sediment transport occurring down-drift of the adjacent up-drift groin (Figure 5-10). This results in an incremental reorientation of the beach between the groins to be more parallel to incoming crests of waves. Longshore transport capacity of incoming waves is reduced by this reorientation. Groins in a field are usually spaced a distance 2 to 3 times their length. A groin field may stretch across enough of a littoral cell to allow a smooth transition to an adjacent reach where artificial response to erosion is no longer necessary. Arranging a taper at the down-drift end of a groin field is a design approach for a gradual transition to an adjacent natural beach. Down-drift Up-drift Figure Concept sketch of a groin field tapered at its down-drift end for a gradual transition to the natural beach alignment. A terminal groin is one located just up-drift of a sediment sink where longshore transport is disrupted and longshore sediment is naturally lost to the nearshore zone. A terminal groin accumulates sediment to the limit of its capacity and widens the beach at a place where sediment leaves the cell, not to return. The change in shoreline orientation at the end of an island, isthmus, or spit is often a place where sediment leaves the littoral cell. These locations are target sites for a terminal beach groin (Figure 5-11). A terminal groin may be appropriate at the down-drift boundary of a beach nourishment project (Figure 5-12). The Alaska Department of Transportation and Public Facilities installed a terminal groin at the inlet to the Nick Dudiak fishing lagoon on Homer Spit, in combination with a dynamically stable beach fill. Beach groin design should be accomplished only by well-qualified coastal engineers. The evolution of the shoreline following groin placement may be simulated with computer models to optimize groin geometry, which is good practice. Good practice would also include a post-construction monitoring program to watch for predefined conditions warranting groin modification, removal, or beach nourishment.

97 Responses to Coastal Erosion in Alaska in a Changing Climate 91 Figure On Cape Canaveral, Florida, jetties at coastal inlets serving as terminal beach groins trap sediment to keep it from building shoals in an adjacent navigation channel. U.S. Army Corps of Engineers photo. Figure A terminal groin protects a beach nourishment project at East Rockaway, New York. U.S. Army Corps of Engineers photo.

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99 CHAPTER6 Permitting Requirements All of the response options to coastal erosion except for the do nothing option will require permitting from different local, state, and federal agencies. Permits that may be required include the following. City or Borough Land Use or Land Management Permits Alaska Coastal Management Program (ACMP) Coastal Project Questionnaire and Certification Statement (prior to 2011) Alaska Department of Environmental Conservation Stormwater Discharge Permit Stormwater Pollution Prevention Plan Alaska Department of Fish and Game Permit Alaska Department of Natural Resources Permit U.S. Army Corps of Engineers Clean Water Act Section 404 Permit U.S. Bureau of Land Management Right of Way Permit U.S. Fish and Wildlife Consultation U.S. Coast Guard Permit U.S. Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) Permit Federal Aviation Administration Permit Federal Energy Regulatory Commission Permit U.S. Forest Service Permit 93

100 94 Chapter 6 Permitting Requirements Local Permits Typically local governing entities (city or borough governments) have jurisdiction over setbacks, fill and grading operations, structures, and drainage projects. They may require a review and public hearing for any action taken to control erosion, especially with regard to potential impact to neighboring properties. Local entities may issue a building permit, or permissions and rights-of-way by other titles for access to property by heavy equipment or other local requirements, including those related to the applicable Coastal Zone Management Plan (see Alaska Coastal Management Program below). State of Alaska Permits Alaska Coastal Management Program The Alaska Coastal Management Program (ACMP) until 2011 was the state implementation of the Coastal Zone Management Act of 1972 (see This program aimed to ensure that all aspects of a project are considered in a single review and approval process. The ACMP required that projects in Alaska s coastal zone be reviewed by coastal resource management professionals and be found consistent with the statewide standards of the ACMP. A finding of ACMP consistency was required before various agency permits could be issued for the project. Since the Alaska State Legislature, with the approval of the governor, did not renew the ACMP in 2011, the program has ceased to exist. The rearrangement of the ACMP clearinghouse function for regulatory actions of other agencies was not defined, as of this writing. Other agencies, certainly those of the federal government, will continue to exercise stewardship of public resources in the coastal zone with significant public involvement. Coastal residents and others with concerns about poorly designed projects causing harm to the Alaska coast will have to be more vigilant and proactive for their voices to be heard without coordination of the ACMP. Alaska Department of Environmental Conservation The Alaska Department of Environmental Conservation (DEC) issues permits for stormwater discharge, which may be applicable to erosion control projects. They also review the Stormwater Pollution Prevention Plan (SWPPP) to ensure it is in compliance with the National Pollutant

101 Responses to Coastal Erosion in Alaska in a Changing Climate 95 Discharge Elimination System (NPDES) General Permit for Large and Small Construction Activities. A SWPPP is required for all projects that disturb an area greater than one acre in size. Information regarding the SWPPP can be found at swppp.cfm. Alaska Department of Fish and Game The Alaska Department of Fish and Game (ADFG) will review a coastal project to ensure that it does not adversely impact any anadromous fish streams or other habitats. Alaska Department of Natural Resources The Alaska Department of Natural Resources (DNR) has jurisdiction over tidelands below Mean High Water (MHW) extending to a point 3 miles offshore. A permit and/or easement may be required for any project within this area. Any material dredged or excavated from this area will also require a permit and may also require a material sale from DNR. The DNR fact sheet that has information for material sales is at Federal Permits U.S. Army Corps of Engineers The U.S. Army Corps of Engineers (USACE) is the main agency involved with permitting for constructed coastal erosion response projects. In accordance with Section 10 of the River and Harbor Act of 1899, the USACE has jurisdiction over the navigable waters of the United States, which includes coastal waters subject to tidal action shoreward of the Mean High Water (MHW) line and inland waters used or may be used for interstate of foreign commerce. In addition, Section 404 of the Clean Water Act extends the USACE jurisdiction to include tributaries and wetlands adjacent to the navigable waters of the United States. A standard USACE permit application form is submitted along with a location and description of the project, drawings, schedule, adjacent property owners, adjacent structures, and approvals from other federal, state, and local authorities. Information regarding the regulatory program of the USACE in Alaska can be found at The USACE has adopted a number of General Condition Permits on a nationwide basis, also known as Nationwide Permits (NWP). The General

102 96 Chapter 6 Permitting Requirements Condition Permits are established to reduce paperwork and delay for certain activities having minimal impacts. Most of the NWPs require notification to the USACE and written verification prior to conducting the work. A summary of NWPs can be found at army.mil/reg/nwps/nwp%20comparison%20table.pdf. U.S. Bureau of Land Management The U.S. Bureau of Land Management (BLM) requires a Right of Way Permit or Land Use Permit to conduct operations on BLM-managed federal land. They may also issue a material sale for the acquisition of sand, gravel, or rock from BLM land. U.S. Fish and Wildlife Service The U.S. Fish and Wildlife Service (USFWS) provides consultation regarding effects to threatened or endangered species under the Endangered Species Act of 1973 and regarding effects to fish and wildlife resources under the Fish and Wildlife Coordination Act. The USFWS will also issue a Letter of Authorization under the Marine Mammal Protection Act for the incidental take of marine mammals. U.S. Coast Guard The U.S. Coast Guard (USCG) has jurisdiction over the navigable waters of the United States. The USCG issues permits for bridge construction, private aids to navigation, and hazards to navigation. The Waterways Management Division of the 17 th U.S. Coast Guard District, located in Juneau, administers these permits (see d17%20divisions/dpw/dpw.asp). U.S. Environmental Protection Agency The U.S. Environmental Protection Agency (EPA) issues a National Pollution Discharge Elimination System (NPDES) Permit under Section 402, Federal Water Pollution Control Act of 1972, as amended (Clean Water Act; 33 USC 1251) for discharges into waters of the United States. Federal Aviation Administration The Federal Aviation Administration (FAA) issues permits for projects located near airports or that extend into the flight path of aircraft.

103 Responses to Coastal Erosion in Alaska in a Changing Climate 97 Federal Regulatory Energy Commission The Federal Regulatory Energy Commission (FERC) issues permits for work that is related to hydroelectric projects, transmission lines, or natural gas pipelines, or that will utilize water from a federal dam. U.S. Forest Service The U.S. Forest Service (USFS) issues permits for projects located on or whose access will cross National Forest land or other land managed by the USFS. Table 6-1 is a checklist provided as an aid to planners. The information in Table 6-1 may not be current or complete, so the reader is advised to contact all agencies to ensure full permitting compliance for any coastal project.

104 98 Chapter 6 Permitting Requirements Table 6-1. Preliminary permitting checklist applicable to coastal erosion response measures in Alaska. Does your project: Permit or form Agency Involve work within a local or borough jurisdiction? Include a stormwater discharge/ collection system? Construct, install, modify, or use any part of a wastewater disposal system? Involve work or construction within a designated state game refuge, critical habitat area, or state game sanctuary? Involve work or construction on stateowned land or water, or will you need to cross state-owned land for access? Involve dredging, excavation, or other removal of materials on state-owned land? Involve placement of fill or dredged material on state-owned land? Impact historical, archaeological, or paleontological resources (anything over 50 years old) on state-owned land? Involve work or construction within a known geophysical hazard area? Involve work in, remove water or material from, or place anything in, a stream, river, or lake? Involve dredging or placement of structures or fills in tidal waters, streams, lakes, or wetlands? Involve work or construction on BLM land, or cross BLM land for access? Varies Approval Permit Approval Land Use Material Sale Land Use Approval Review Approval Section 404 Permit Land Use Local or borough permitting agency Alaska Department of Environmental Conservation Alaska Department of Environmental Conservation Alaska Department of Fish and Game Alaska Department of Fish and Game Alaska Department of Natural Resources Alaska Department of Natural Resources Alaska DNR Office of History and Archaeology Alaska Department of Natural Resources Alaska Department of Natural Resources U.S. Army Corps of Engineers U.S. Bureau of Land Management Expose one or more acres of soil? NPDES Permit U.S. Environmental Protection Agency Involve work or construction within five miles of any public airport? Involve work or construction on U.S. Forest Service land? Approval Approval Federal Aviation Administration U.S. Forest Service

105 Responses to Coastal Erosion in Alaska in a Changing Climate 99 Concluding Remarks Alaska has a challenging frontier setting that is the pride of its residents. Most coastal communities of the state lie in remote subarctic and arctic locations without road access. Information on winds, water levels, waves, and shoreline processes, if it exists at all, is often of short record. Public interest in making these measurements tends to follow crises. Growing awareness of climate change issues may help justify local, state, and federal investment in useful baseline investigations and monitoring of climatic conditions at more of Alaska s coastal communities. Alaska s shores include a wide diversity of configurations, materials, and exposures to ocean conditions. Each stretch of waterfront is unique in its particular combination of these characteristics. Defining site-specific shoreline circumstances and the physical cause of coastal erosion is an appropriate first step toward erosion responses that will serve well and are worth their cost. Alternative erosion responses are always possible. A declaration of a single good design is suspicious. Low-cost solutions are tempting, but prone to early failure. Long-lasting erosion responses cost more. A wise choice is more certain if based on advice from qualified and experienced professionals. Our universities are providing a new generation of coastal specialists, but should get public support to keep pace with needs of the state. Conservative structural approaches to shore protection can cover uncertainties in knowledge at high cost. Massive rock revetments and steel seawalls can do the job of protecting shoreline property, if well built, but they may change the shoreline forever. No adverse impact to coastal neighbors is a worthy goal. Collaborations of adjacent landowners or community-sponsored coastal erosion responses are typically more effective than action by individual property owners. While centuries of shore protection efforts have refined designs of revetments and seawalls, improvement is always possible. The body of research supporting design of shore protection in high tide ranges and cold climates is still small. Agency and university research along these lines will lead to more affordable and effective designs for Alaska. Beach nourishment is comparatively untried in Alaska as a coastal erosion response. The few Alaska efforts to date have been clouded by logistical pitfalls and limited documentation by which to judge their effectiveness. The Alaska Department of Transportation and Public Facilities has built several dynamically stable beaches in recent years of

106 100 Concluding Remarks material coarser than natural sediments. These projects cost less than conventional revetments and appear to serve well without disruption of prevailing cycles. The agency is planning research to improve its future beach fill and dynamically stable beach designs. Public awareness of coastal issues and challenges is important. This book is meant to contribute toward that end, but more can be done. With coastal erosion so often in the news, high school science teachers can hope for inspiring students toward science and engineering careers as coastal specialists. University programs can also be refined and expanded. Programs for the public can be interesting, informative, and even exciting. Students and others interested in the coast can contribute to the scientific body of knowledge through organized beach observer programs. The State of Alaska is in a position now to contribute to all these means to enhance the future of its coastal resources. Regulatory frameworks exist that can be streamlined toward more effective stewardship. Economic losses are minimal when undeveloped shoreline is changed by erosion. Natural processes, left to themselves, do not harm the environment or deplete the treasury. Public consent to constrain unwise shoreline construction can prevent some broken dreams and costly liabilities. Setback lines could be effective in Alaska, applying lessons learned in other coastal states. A state agency with explicit responsibility for coastal erosion responses could provide positive influence as a partner with the federal government to plan and design response projects whose long-term benefits outweigh costs and whose environmental impacts are positive. Climate change will only increase concerns for the stability of Alaska s great shoreline, which is longer than that of all the rest of the U.S. coastal states. The public service of the state and federal governments cannot take the place of personal responsibility. Due diligence by prospective coastal property owners to investigate the local coastal setting and shoreline processes will hopefully prevent poor decisions. The coast will always be a risky place to build. The National Flood Insurance Program provides one means for individual coastal property owners to protect their investments. Uninsured private property in trouble from coastal erosion does not default to government aid. When nature takes an adverse course toward private property, the first responsibility is that of the property owner.

107 Responses to Coastal Erosion in Alaska in a Changing Climate 101 References Cited Aminti, P., C. Cammelli, L. Cappietti, N. Jackson, K. Nordstrom, and E. Pranzini Evaluation of beach response to submerged groin construction at Marina di Ronchi, Italy, using field data and a numerical simulation model. In: C. Kraus and K.L. Rankin (eds.), Functioning and design of coastal groins: The interaction of groins and the beach process and planning. Journal of Coastal Research Special Issue 33, pp ASFM Coastal no adverse impact handbook. Association of State Floodplain Managers, Madison, Wisconsin. ASTM Standard practice for specifying standard sizes of stone for erosion control. ASTM D , ASTM International, West Conshohocken, Pennsylvania. 13 pp. ASTM Standard guide for placement of riprap revetments. ASTM D , ASTM International, West Conshohocken, Pennsylvania. 7 pp. Basco, D., and J. Pope Groin functional design guidance from the coastal engineering manual. In: C. Kraus and K.L. Rankin (eds.), Functioning and design of coastal groins: The interaction of groins and the beach process and planning. Journal of Coastal Research Special Issue 33, pp Brown, S., and E. Clyde Design of riprap revetment. FHWA-IP HEC-11, Federal Highway Administration, McLean, Virginia. CIRIA The rock manual: The use of rock in hydraulic engineering, 2nd edn. Construction Industry Research and Information Association, Classic House, London, 1200 pp. Donohue, K., L. Bocamazo, and D. Dvorak Experience with groin notching along the northern New Jersey coast. In: C. Kraus and K.L. Rankin (eds.), Functioning and design of coastal groins: The interaction of groins and the beach process and planning. Journal of Coastal Research Special Issue 33, pp Duncan, J.M., and S.G. Wright Soil strength and slope stability. John Wiley and Sons. 312 pp. FEMA Coastal construction manual: Principles and practices of planning, siting, designing, constructing, and maintaining residential buildings in coastal areas, 3rd edn. FEMA mat/fema55.shtm#1, accessed June Greene, K Beach nourishment: A review of the biological and physical impacts. ASMFC Habitat Management Series 7, Atlantic States Marine Fisheries Commission, Washington, D.C. Hinrichsen, D Coastal waters of the world: Trends, threats, and strategies. Island Press, Washington, D.C.

108 102 References Cited Hughes, S Uses for marine mattresses in coastal engineering. CHETN- III-72, U.S. Army Corps of Engineers, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi. 23 pp. Karle, K., N. Moore, and W. Bennet Evaluation of bioengineered stream bank stabilization in Alaska. Alaska Department of Transportation and Public Facilities, Juneau. 206 pp. Mason, O., W, Neal, O. Pilkey, J. Bulluck, T. Fathauer, D. Pilkey, and D. Swanston Living with the coast of Alaska. Duke University Press, Durham. McCartney, B Floating breakwater design. Journal of Waterway, Port, Coastal and Ocean Engineering 111(2): doi: / (ASCE) X(1985)111:2(304) Mulherin, N., W. Tucker, O. Smith, and W. Lee Marine ice atlas for Cook Inlet, Alaska. U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. NOAA Chart no. 1: United States of America nautical chart symbols, abbreviations, and terms, 10th edn. National Oceanic and Atmospheric Administration, Washington, D.C. NOAA Tide and current glossary. National Oceanic and Atmospheric Administration, Silver Spring, Maryland. NOAA Beach nourishment: A guide for local government officials. National Oceanic and Atmospheric Administration Coastal Services Center. accessed June NOAA Final evaluation findings, Alaska Coastal Management Program, October 2002 August National Oceanic and Atmospheric Administration Office of Ocean and Coastal Resource Management. NRC Managing coastal erosion. National Resource Council, National Academy Press, Washington, D.C. NRC Beach nourishment and protection. National Resource Council, National Academy Press, Washington, D.C. PIANC Guidelines for the design and construction of flexible revetments incorporating geotextiles in marine environment. International Navigation Association (PIANC), Brussels. 197 pp. Pilkey, O.H., and K.L. Dixon The Corps and the shore. Island Press, Washington, D.C. Poff, M., M. Stephen, R. Dean, and S. Mulcahy Permeable wood groins: Case study on their impact on the coastal system. In: C. Kraus and K.L. Rankin (eds.), Functioning and design of coastal groins: The interaction of groins and the beach process and planning. Journal of Coastal Research Special Issue 33, pp Revenga, C., J. Everett, and J. Maidens (eds.) UN atlas of the oceans. United Nations. accessed June 2011.

109 Responses to Coastal Erosion in Alaska in a Changing Climate 103 Smith, O.P. (ed.) Coastal erosion responses for Alaska: Workshop proceedings. Alaska Sea Grant College Program, University of Alaska Fairbanks. 80 pp. Smith, O., A. Khokhlov, S. Buchanan, and W. Lee Beach stability measurements and analysis at Nikiski, Alaska. Contract report for Geomega, Inc., and Chevron/Texaco. University of Alaska Anchorage, School of Engineering. Sodhi, D., S. Borland, and J. Stanley Ice action on riprap: Small-scale tests. CRREL 96-12, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. 70 pp. Suleimani, E.N., R.A. Combellick, D. Marriott, R.A. Hansen, A.J. Venturato, and J.C. Newman Tsunami hazard maps of the Homer and Seldovia areas, Alaska. Alaska Division of Geological and Geophysical Surveys. Terzaghi, K., R. Peck, and G. Mesri Soil mechanics in engineering practice, 3rd edn. John Wiley and Sons. 592 pp. USACE Coastal groins and nearshore breakwaters. EM , U.S. Army Corps of Engineers, Washington, D.C. USACE Design of coastal revetments, seawalls, and bulkheads. EM , U.S. Army Corps of Engineers, Washington, D.C. 110 pp. USACE Shore protection projects. Coastal engineering manual. EM , U.S. Army Corps of Engineers, Washington, D.C. usace.army.mil/cem, accessed June USACE Alaska baseline erosion assessment: Study findings and technical report. U.S. Army Corps of Engineers Alaska District, Anchorage. accessed June Zevenbergen, L., P. Lagasse, and B. Edge Tidal hydrology, hydraulics, and scour at bridges. HEC-25, U.S. Federal Highway Administration.

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111 Responses to Coastal Erosion in Alaska in a Changing Climate 105 Glossary The following definitions are adapted from the U.S. Army Corps of Engineers Coastal Engineering Manual (USACE 2008), the NOAA Tide and Current Glossary (NOAA 2000), and common usage. accretion accumulation of beach material, often advancing the shoreline seaward. alluvial deposit material transported and deposited by a river or stream, commonly silts, sands, and gravels. alluvial fan a fan-shaped alluvial deposit at the coast, typical of the mouths of mountain streams along otherwise steep rocky shores. alongshore parallel to the shoreline; same as longshore. armor stone or unit a large rock or concrete block selected or formed to fit weight and shape criteria for placement on the outer slope of a revetment or breakwater. The unit armors the slope beneath against wave attack. backshore the zone between the foreshore and the shoreline that is affected by waves only during severe storms. bar a submerged or partially submerged elongated shoal or mound of sediment created by wave action or current. barrier island long, narrow, low-lying islands running parallel to the mainland and separated from it by a shallow lagoon. bathymetry comprehensive information on depths and depth trends of a water body. Bathymetric information deals with depths and the shape of the seafloor. beach a zone extending from the low tide line landward to a major change in material or form, often defined by the landward reach of storm waves. beach fill (nourishment) placement of fill material, usually sand or gravel, on a beach to restore or create habitat, recreational surface, and protection of landward property. bench mark a fixed object or mark used as a reference for a vertical datum. A tidal bench mark is a bench mark to which tidal datums are referred. berm a horizontal plateau on the beach or backshore formed by wave action or placed as part of a beach nourishment program. bluff a steep cliff-like bank composed primarily of soil. borrow sediments excavated from one site to be placed as fill at another site. breaker zone a nearshore zone usually parallel to shore where shallow depths induce wave breaking; also called the surf zone. breaking collapse of a wave, induced at the shore by depths too shallow to allow wave form stability.

112 106 Glossary breakwater a structure that provides protection from waves for a harbor or reach of shoreline on its landward side. bulkhead a structure built to hold the ground behind and sometimes to protect the land from wave damage. caisson a massive chamber placed underwater as a foundation. cliff a high, steep bank composed primarily of rock. coastal zone (legal definition for U.S. Coastal Zone Management) the coastal waters (including the lands therein and thereunder) and the adjacent shorelands (including the waters therein and thereunder), strongly influenced by each and in proximity to the shorelines of the several coastal states, and includes islands, transitional and intertidal areas, salt marshes, wetlands, and beaches. The zone extends, in Great Lakes waters, to the international boundary between the United States and Canada and in other areas seaward to the outer limit of the U.S. territorial sea. The zone extends inland from the shorelines only to the extent necessary to control shorelands, the uses of which have a direct and significant impact on the coastal waters. Excluded from the coastal zone are lands the use of which is by law subject solely to the discretion of or which is held in trust by the federal government, its officers, or agents. cobble stone with a diameter between 3 and 10 inches, often rounded. crest the highest part of a wave. cross-shore directed from the land to the sea or vice-versa. datum a base elevation used as a reference from which to measure heights or depths. A tidal datum is defined in terms of a specific phase of the tide. Tidal datums are local datums and should not be extended from one coastal area into another with different coastal characteristics. Tidal datums are referenced to fixed points known as (tidal) bench marks. deep water water whose depths are so great that wave behavior is not affected; depths greater than half the wavelength. delta an alluvial deposit at the mouth of a river or stream. A tidal delta is a similar deposit at the mouth of a tidal inlet. diffraction reduction of wave height when a wave spreads into the shadow zone behind a barrier. diurnal having a period or cycle of approximately one tidal day. A tide is diurnal when only one high-water and one low-water occur during a tidal day, and the tidal current is diurnal when there is a single flood and single ebb period of a reversing current in the tidal day. dolos (plural dolosse) a prefabricated concrete block in a complex geometric shape weighing up to 20 tons, used in place of large rock as an outer armor layer for harbor breakwaters and revetments. down-drift predominant direction toward which wave-induced movement of littoral materials flow. dredging underwater excavation of sediments.

113 Responses to Coastal Erosion in Alaska in a Changing Climate 107 ebb period of time when tide is falling. The associated flow is ebb current, typically away from shore or down a tidal river or estuary. erosion the wearing away of the land by natural forces. estuary a coastal embayment in which fresh river water mixes with saline ocean water. Tidal action is the dominant mixing agent in a tidal estuary. fetch the distance over which the wind blows with steady speed and direction to generate waves. filter intermediate layer of material in a revetment that prevents finer material beneath from being washed through the voids of the upper layer. fjord a glacier-formed estuary with steep mountainous shores and a U-shaped cross-section, usually very deep, but sometimes segmented by a shallower transverse moraine. flood (1) Period of time when the tide is rising. The associated flow is flood current, typically toward shore or up a tidal river or estuary. (2) Extreme high water level caused by flow beyond the capacity of a channel. foreshore the lower part of the shore normally wetted and otherwise affected by wave action. gabion wire-mesh rectangular basket to hold stones or sandbags, usually wired together to form a wall or slope for bank protection against erosion. geotextile a synthetic woven fabric or perforated membrane used as a filter to separate soil and rock. glacial till unstratified, intermingled sediment of glacial origin consisting of unsorted clay, sand, gravel, and boulders. groin narrow man-made structure built perpendicular to the shore to retain littoral material on one side. headland a point of land or promontory extending out into a body of water. High Water the maximum height reached by a rising tide. inlet (1) A short, narrow waterway connecting a bay, lagoon, or similar water body with a large parent water body. (2) An arm of the sea (or other water body) that is long compared to its width and may extend a considerable distance inland. intertidal zone the zone between the Mean Higher High Water and Mean Lower Low Water lines or, more usually, the tidelands routinely wetted and dried by tidal action. isostatic rebound uplift of the earth s crust in relief from the weight of continental glaciers during the last ice age; also called glacial rebound. jetty a structure extending into a body of water that is designed to prevent shoaling of a channel on one side from littoral materials arriving on the other side and to confine and direct the stream or tidal flow. lagoon a shallow water body separated from the sea by a barrier island, spit, or reef.

114 108 Glossary leeward on the downwind side or on the sheltered side of a wave barrier. liquefaction the condition of quicksand and other soil when friction between grains is ineffective and the soil behaves as a liquid. littoral of or pertaining to the coastal zone influenced by wave action. littoral cell a reach of coast that is substantially isolated by headlands, inlets, or submarine canyons from the adjacent coast in terms of sediment sources and sinks. littoral drift longshore sediment transport induced by waves breaking in a prevailing direction. littoral zone the strip along the shoreline that is influenced by wave action. longshore parallel to and near the shoreline; same as alongshore. longshore current current in the breaker zone moving essentially parallel to the shoreline and usually caused by waves breaking at an angle to shore. longshore transport movement of littoral material parallel to the shoreline. The longshore transport rate is usually expressed in cubic yards per year. Low Water (LW) the minimum elevation reached by a falling tide. Mean High Water (MHW) a tidal datum. The average of all the High Water heights observed over the National Tidal Datum Epoch. For stations with shorter series, simultaneous observational comparisons are made with a control tide station in order to derive the equivalent datum of the National Tidal Datum Epoch. Mean Higher High Water (MHHW) a tidal datum. The average of the Higher High Water height of each tidal day observed over the National Tidal Datum Epoch. For stations with shorter series, simultaneous observational comparisons are made with a control tide station in order to derive the equivalent datum of the National Tidal Datum Epoch. Mean Lower Low Water (MLLW) a tidal datum. The average of the Lower Low Water heights of each tidal day observed over the National Tidal Datum Epoch. For stations with shorter series, simultaneous observational comparisons are made with a control tide station in order to derive the equivalent datum of the National Tidal Datum Epoch. Mean Sea Level (MSL) a tidal datum. The arithmetic average of hourly heights observed over the National Tidal Datum Epoch. Shorter series are specified in the name, e.g., monthly Mean Sea Level and yearly Mean Sea Level. Mean Tide Level (MTL) the arithmetic average of Mean High Water and Mean Low Water; may be different from Mean Sea Level (MSL). moraine an accumulation of rocks and sediments deposited by a glacier, usually in the form of a mound or ridge.

115 Responses to Coastal Erosion in Alaska in a Changing Climate 109 National Tidal Datum Epoch the specific 19-year period adopted by the National Ocean Service as the official time segment over which tide observations are taken and reduced to obtain mean values (e.g., Mean Lower Low Water) for tidal datums. It is necessary for standardization because of periodic and apparent secular trends in sea level. It is reviewed annually for possible revision and must be actively considered for revision every 25 years. nautical charts maps of the seafloor and shoreline, published by NOAA, primarily for use by mariners; definitions of symbols and conventions on nautical charts are published by NOAA in the book Chart No. 1 (NOAA 1997). nearshore (1) In beach terminology, an indefinite zone extending seaward from the shoreline well beyond the breaker zone. (2) The zone that extends from the swash zone to the position marking the start of the offshore zone, typically at water depths of 60 feet. offshore in the direction away from land toward the open sea; in deep water, well beyond the surf zone. onshore in the direction toward land away from the open sea. overtopping passing of water over a structure from wave runup or surge action. permafrost permanently frozen soil, underlying a layer of soil that freezes and thaws with the seasons. Seasonal layers deepen as permafrost melts due to global warming. Permafrost composed of silt and clay soil grains with high water content is prone to subside on melting as liquid water flows away leaving a weak soil matrix behind. permeability the property of a material to permit passage of water through its pores. plunging breaker a breaking wave whose crest curls forward to form a tube, much favored by surfers. pocket beach a small beach between two shore barriers. quarrystone large rocks from a quarry. range (of tide) the difference in height between consecutive high and low waters. The mean range is the difference in height between Mean High Water (MHW) and Mean Low Water (MLW). The diurnal range is the difference in height between Mean Higher High Water (MHHW) and Mean Lower Low Water (MLLW). reef offshore consolidated rock that is a hazard to navigation, with a least depth of 60 feet (10 fathoms) or less. refraction (of water waves) the process by which the direction of a wave moving in shallow water at an angle to the contours is changed. Part of the wave advancing in shallower water moves more slowly than the part still advancing in deeper water, causing the wave crest to bend toward alignment with the underwater contours.

116 110 Glossary revetment facing of stone, concrete, etc., built to protect a scarp, embankment, or shore structure against erosion by waves or currents. riprap a protective layer or facing of quarry stone, usually well graded within a wide size limit, randomly placed to prevent erosion, scour, or sloughing of an embankment or bluff; also the stone so used. The quarry stone is placed in a layer at least twice the thickness of the 50 percent size, or 1.25 times the thickness of the largest size stone in the gradation. runup the rush of water up a structure or beach upon the breaking of a wave. Amount of runup is the vertical height above Still Water Level (SWL) that the rush of water reaches. salt marsh a wetland periodically flooded by salt water. sand coarse grained soil, usually composed of quartz but may be calcareous reef debris or shell fragments. Grain size is between silt and gravel (0.074 mm to 4.75 mm). scour removal of underwater material by waves or currents, especially at the base or toe of a shore structure. seawall a structure, often composed of concrete or stone, built along a portion of a coast to prevent erosion and other damage from wave action. Often built as a bulkhead to retain earth against its landward face. sediment (1) Loose fragments of rocks, minerals, or organic material transported from their source for varying distances and deposited by air, wind, ice, and/or water. (2) Material that is precipitated from the overlying water or forms chemically in place. Sediment includes all the unconsolidated materials on the seafloor. sediment budget an application of the principle of conservation of mass that involves estimating influx and discharge of sediment from a control volume, such as a littoral cell. The difference results in either accumulation or loss (erosion) of sediment within the littoral cell. This systematic approach to understanding coastal trends leads to well-informed choices among coastal erosion response alternatives. sediment transport the main agencies by which sedimentary materials are moved are gravity, running water (rivers and streams), ice (glaciers and pack ice), wind, and the sea (currents and longshore drift). setback (line) a prescribed distance from Mean High Water, typically established by a governing body to regulate nearshore construction. shallow water water of such a depth that surface waves are noticeably affected by bottom topography; usually depths less than half the surface wavelength. sheet pile pile made of steel or aluminum, with a flat Z-shaped cross-section, driven into the ground or seabed and meshed or interlocked with like members to form a wall or bulkhead. shingle any beach material coarser than ordinary gravel, especially flat shaped.

117 Responses to Coastal Erosion in Alaska in a Changing Climate 111 shoal (1) (noun) A detached area of any material except rock or coral in which the water depths over it are a danger to surface navigation. (2) (verb) To become shallow gradually. (3) To cause to become shallow. (4) To proceed from a greater to a lesser depth of water. shoaling with regard to wave behavior, changes induced by increasingly shallow depths less than half the wavelength. shoreline (coastline) the intersection of the land with the water surface. The shoreline shown on charts represents the line of contact between the land and a selected water elevation, usually Mean High Water. sill a low offshore barrier structure whose crest is usually submerged. Fjords often have one or more sills formed by submerged moraines. silt fine-grained soil that exhibits low plasticity characteristics with a grain size smaller than mm. sink a place where sediments are permanently lost from the littoral zone, such as a submarine canyon, in the mass-balance context used in this book. slope degree of inclination to the horizontal, usually expressed as a ratio, such as 1:25 indicating one unit rise in 25 units horizontal distance, or in degrees from horizontal. spilling breaker a breaking wave with foamy collapse of the crest down the oncoming face of the wave. spit a small point of land or a narrow shoal projecting into a body of water from the shore. spring tides (tidal currents) tides of increased range or tidal currents of increased speed occurring semimonthly as the result of the moon being new or full. Still Water Level (SWL) elevation that the surface of the water would assume if all wave action were absent. storm surge a departure from a normal elevation of the sea due to the piling up of water against a coast by strong winds such as those accompanying a hurricane or other intense storm. Reduced atmospheric pressure contributes to the departure in height during hurricanes and intense extratropical storms. surf breaking waves. surf zone the band of water along the shore in which waves are breaking. swell wind-generated waves traveling out of their generating area. Swell characteristically exhibits a more regular and longer period, and has flatter crests than waves within their fetch. tidal current a horizontal movement of the water caused by gravitational interactions between the sun, moon, and earth and the associated movement of the ocean manifested in the vertical rise and fall called tide.

118 112 Glossary tidal flats marshy or muddy areas covered and uncovered by the rise and fall of the tide. tide or tides the periodic rise and fall of the water resulting from gravitational interactions between the sun, moon, and earth. tidelands area of the shore covered and uncovered by tidal water level fluctuations. As applied to define land ownership, the zone between the Mean High Water and Mean Low Water lines. toe lowest part of an embankment, breakwater, or slope. tombolo a sand or gravel bar connecting an island with the mainland or another island. trough the lowest part of a wave. tsunami a shallow-water wave, potentially catastrophic, caused by an underwater earthquake or volcano. unconsolidated a condition of sediments in which grains are loose, separate, and unattached to one another. undercutting erosion of material at the foot of a cliff or bank. Ultimately, the resulting overhang collapses and the process is repeated. uplands land above the Mean High Water line that can be privately owned, as distinguished from tidelands, usually owned by the state. wale(r) a horizontal beam on a bulkhead used to laterally transfer loads against the structure and hold it in a straight alignment. wattling rows of stakes interwoven with branches or other pliant material. wave an undulation of the surface of a liquid. wave crest highest part of a wave. wave direction direction from which a wave approaches. wave height vertical distance between the wave crest and the preceding wave trough. wave period time for two successive wave crests to pass a fixed point. wave steepness the ratio of wave height to wavelength. wave trough lowest part of a wave between successive wave crests. wavelength the horizontal distance between two successive wave crests. wetlands lands whose saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities that live in the soil and on its surface. windward the direction from which the wind is blowing.

119 Responses to Coastal Erosion in Alaska in a Changing Climate 113 Index (Pages with photos or graphics are bold.) Alaska Coastal Management Act 59 Alaska Coastal Management Program 4, 46, 59, 94 Alaska Department of Environmental Conservation 94 Alaska Department of Fish and Game 95 Alaska Department of Natural Resources 59, 95 Alaska Department of Transportation and Public Facilities 58 Alaska Division of Geological and Geophysical Surveys 59 Alaska Ocean Observing System 25 Alaska Peninsula Aleutian Islands 35 alluvial fan 18, 19 Anchorage, Alaska 29 tide records 29 arctic Alaska coast barrier island 42 coastal river delta 42 map 40 avalanche 21 barrier islands, arctic Alaska 42, 43 Barrow, Alaska, gabion seawall 74 beach fill 52 placement 84 spreading losses 86 beach groins 52, 56-57, groin field 90 impact 89 wooden crib 88 beach nourishment 51, 52, cross-section 81 design dynamically stable beaches evaluation 83 fill placement 84 Bering Sea, map 18, 36, 35 bluff erosion 32, 33 arctic Alaska 43 breakwaters Brooklyn, New York, shore protection 79 Cape Canaveral, Florida, jetties as groins 91 Chukchi Sea coast 41 map 18 waves 8 coastal zone management Coastal Zone Management Act 4, 46 concrete, precast revetment Cook Inlet, Alaska bluff erosion 32 map 23, 27 steep bluffs 28 tidal flats 28 tide ranges 29 wind 6 Dillingham, Alaska, seawall 70 earthquake 25 and landslides 21 and sea level rise 13 and slope collapse 18, 21 East Rockaway, New York, groin 91 erosion control beach groins 56-57, beach nourishment 51, 52, breakwaters infiltration and drainage control 51 revetments 53, 54, seawalls 53-55, slope reduction 51 vegetation 50 federal efforts to address erosion Federal Emergency Management Agency 48

120 114 Index flood-proofing piling foundation 49 Glacier Bay National Park, Beartrack Mountain 21 glaciers, ice age 22, 25, 27 global warming 40 glossary groins, beach 52, groin field 90 impact 89 wooden crib 88 Gulf of Alaska coast map 18 Hawks Beach, Alaska, seawall 71 Homer, Alaska digital elevation data 24 groin 90 seawall 55, 73 tsunami inundation risk 32 Indiana Dunes National Lakeshore beach nourishment 77 Juneau, Alaska, sea level fall 23 Kenai Fjords National Park, pocket beach 20 Kivalina, Alaska revetment 57, 58 sediment transport 14 waves 8 Kodiak archipelago, Alaska liquefaction 29 Lowell Point, Alaska building 49 sea level rise 13 tombolo 56 marine mattress revetment Maui, Hawaii, revetment 62 moon, effect on tides 10 National Coastal Zone Management Program 46 Nikiski, Alaska pre-beach nourishment 79, 80 waves 8 wind 6 Ninilchik, Alaska, beach groins 88 No Adverse Impact philosophy 60 Nome, Alaska seawall 59 storm surge 12 storm waves 38 tides 11 permafrost arctic Alaska 43 map 39 western Alaska 38 permitting requirements pocket beach 18, 20 Prince William Sound, Alaska 25 map 24 Prudhoe Bay, Alaska, coast 42 relocation 50 responses to erosion revetments 53, 54, 58, 60-70, 62 design checklist 65 failure of 64, 68-70, 69 marine mattresses precast concrete riprap rock 49 riprap revetment river delta 18, 19 rock revetment 49 sand dunes arctic Alaska 41 western Alaska 37 sea ice arctic coast 38 in Cook Inlet 33, 34 and erosion 16 sea level fall 23 rise 13-14, 22 seawalls 52, 53-55, barrier 72, 74 gabion 73-75, 74 profile retention 72 scour damage 73 scour protection 73 sheet-pile 70, 72 sediment transport, shoreline 14-16, 15 setback lines 47 Seward, Alaska alluvial fan 19 wind 6 sheet-pile seawall 71, 72 Shishmaref, Alaska failed revetments 69 failed seawall 75 revetment 54, 57 shoreline processes 5

121 Responses to Coastal Erosion in Alaska in a Changing Climate 115 slip circle slope failure 30 slope stability southcentral Alaska map 23 southeast Alaska map 20 storm surge western Alaska 38 Taku Inlet, Alaska river delta 19 thermal niche 43, 44 tidal currents 22 tidal flats 28 tides arctic Alaska 40 southeast Alaska 22 tombolo 56 Trans-Alaska Oil Pipeline terminus 26 tsunami inundation risk 32, 33 Unalakleet 57 U.S. Army Corps of Engineers 95 Low Cost Shore Protection program iv wavelength 7 waves 6-10, 8 vessel-generated 10 western Alaska 35 bluffs 37 map 36 sand dunes 37 wind 5-6 wind rose 6 Yakutat, Alaska, coast 21

122 Also from Alaska Sea Grant Coastal Erosion Responses for Alaska: Workshop Proceedings Orson P. Smith (editor), 80 p. alaskaseagrant.org/bookstore/pubs/ak-sg html Living on Alaska s Changing Coast: Adapting to Climate Change in Coastal Alaska Website with 8 publications and 2 DVDs marineadvisory.org/climate/index.php Adapting to Climate Change in Alaska 17 min DVD alaskaseagrant.org/bookstore/pubs/m-135.html Community-Based Coastal Observing in Alaska: Aleutian Life Forum 2006 Reid Brewer (editor), 111 p. alaskaseagrant.org/bookstore/pubs/ak-sg html Northern Harbors and Small Ports: Operation and Maintenance Alan Sorum, 162 p. alaskaseagrant.org/bookstore/pubs/mab-56.html Rat Control for Alaska Waterfront Facilities Terry Johnson, 106 p. alaskaseagrant.org/bookstore/pubs/mab-62.html Monitoring Changes in Alaska s Coastline Reid Brewer (editor), 12 p. alaskaseagrant.org/bookstore/pubs/m-68.html