Erosion Prevention at Mosquito Point, Northern Neck, Virginia

Transcription

1 Erosion Prevention at Mosquito Point, Northern Neck, Virginia Michael S. Fenster Advanced Environmental Problem Solving Class - EVST 305/405, Spring 2009 Randolph-Macon College Environmental Studies Program Ashland, VA TECHNICAL REPORT: RMC-EVST Photographs taken by M. Fenster (top) and RMC students (bottom) Submitted to the Estate of Ms. Betty Price January 2011

2 PRELUDE Environmental professionals must be adept at identifying the issues that comprise a complex environmental problem, skillful in gathering the information necessary to understand the issues, creative in developing holistic solutions and productive in interdisciplinary teams. The Environmental Studies (EVST) major at Randolph-Macon College teaches students these skills using actual issues facing a community and students work with clients and community members in developing the analysis. The erosion situation at Mosquito Point served as the project on which junior- and senior-level undergraduate Environmental Studies students worked during the spring semester, The EVST curriculum enables students with expertise in diverse areas (specific disciplines) to analyze and develop solutions to complex environmental problems. For this project, students used their areas of expertise to analyze the historical and current physical processes that affect Mosquito Point, determine the demographic composition of the residents, assess desired solutions among residents and homeowners, identify relevant shoreline protection policies and determine the economic viability of various solutions. The following students of the EVST 305/405 Environmental Problem Solving class conducted the work for this project, performed the analyses and wrote this report: Alexander, Stephen D. Moline, Christopher S. Blocker, Abby Noyes, Catherine Carroll, Will D. Rash, Megan E. Craun, Steven K. Rowe, Benjamin R. Deem, Mayjean L. Schwarz, Michael V. Ebert, Christine L. Sheads, Dillon T. Ferguson, Ashley A. Weatherly, Andrew A. Hall, Faith A. White, Shannon L. Harris, Joshua G. Williamson, Arba G., IV Kachuba, Gabriel M. Wilson, Laura L.

3 TABLE OF CONTENTS CHAPTER 1: Introduction Study Area... 2 CHAPTER 2: Physical Science Analysis Introduction Shoreline Change Beach Profiling Sediment Analysis Wave Dynamics Wave Refraction Modeling Water Quality Conclusion- The Big Picture CHAPTER 3:Sociological Analysis Introduction Survey Methods Community Involvement and Grant Research Methods Survey and Data Analysis Conclusion CHAPTER 4: Policy Analysis Introduction Federal Policies State Policies Local Policies CHAPTER 5: Economic Analysis Introduction Hard Structures Soft Solutions Hybrid Structures Recommendations References Appendix I... 48

4 CHAPTER 1. INTRODUCTION Beaches change rapidly in response to hydrologic and atmospheric forces that work synergistically over time and in space. For example, sea level rises at hardly noticeable rates of approximately 2 mm per year globally (Church and White, 2006) while large storm waves can diminish a particular beach in a matter of hours. In addition to inundating low-lying coastal areas, rising sea level increases the vulnerability of coastal regions to flooding caused by storm surges and extreme astronomic tides (FitzGerald et al., 2008). As sea levels rise, storm waves and astronomic tides of a given height reach higher and higher coastal elevations which, in turn, results in more extensive areas of inundation especially if engineering structures inhibit or prevent the natural migration of coastal sediment. Moreover, storm surges of a given elevation will occur more frequently in any given location. In short, rising sea levels will cause storm surges to increase the frequency with which waves will wash over the top of beaches and threaten coastal development. The suite of processes that work together on beaches can result in substantial beach erosion. Beach erosion occurs when (1) the fluid forces that cause sediment to move win the constant tug-of-war against the physical forces that resist sediment movement (for example, gravity) and (2) more sediment leaves an area than comes into that area from elsewhere. Erosion is particularly problematic along the United States east coast where 86% of beaches have experienced erosion within the last 100 years (Fenster and Dolan, 1994). Coastal scientists work to determine the magnitudes, directions, and causes of sediment transport within these complex systems. Erosion has forced coastal homeowners and business owners to implement a variety of shoreline protection strategies. These methods typically fall into one of three categories: hard structures, soft prevention, and hybrid options. Hard structures typically include shore-perpendicular devices such as groins; and shore-parallel structures such as seawalls, bulkheads, revetments, breakwaters, and any other installed structure designed to absorb wave energy and/or to prevent sediment transport. Soft prevention methods include creating new or restoring existing beaches by adding sand from another source, building dunes and/or stabilizing mobile sediment with vegetation. During the last decade, hybrid-type projects constructed with a combination of hard and soft approaches have been employed to mitigate beach erosion and maintain productive habitats (Burke et al., 2005). Coastal scientists have learned that installation of hard structures, such as seawalls, revetments, and groins can exacerbate natural erosion processes (Tait and Griggs, 1990). Seawalls and revetments in effect, fix the shoreline position which, in turn, prevents the long-term natural maintenance of beach systems that would exist under natural conditions. Moreover, when vegetation is scarce, sediments become more vulnerable to erosion; thus, development pressures that reduce vegetation on coasts play a role in magnifying the impacts of the process (Halka, 2005). This report focuses on: (1) determining the processes responsible for shoreline trends at one location on the Rappahannock River adjacent to the Chesapeake Bay and (2) recommending strategies for mitigating problematic erosion trends at that location. In particular, this study recommends erosion prevention methods for a natural (unarmored) section of beachfront property on Mosquito Point, Virginia (henceforth, The Point ) owned by Ms. Betty Price. Mosquito Point homeowners were concerned that continued erosion trends occurring to the beaches along The Point would result in a loss or destruction of homes and property. In response, The Point homeowners have utilized a variety of erosion management methods during the past 30 years that include riprap and timber revetments, bulkheads and groins, as well as vegetative buffers. In 2008, Ms. Price approached the Environmental Studies Program at Randolph-Macon College (RMC) to develop a natural solution to the apparent erosion occurring along her beachfront property (henceforth, The Property ). In addition, Ms. Price desired that the solution also promote environmental conservation. Students enrolled in an advanced environmental problem-solving course at RMC undertook this project. During the spring semester, 2009, twenty students (juniors and seniors) worked to determine the best erosion prevention method available for Ms. Price, taking into account biological, geological, sociological, political, and economic factors. 1

5 To accomplish the above goals, students worked in groups based on their areas of expertise: (1) Physical Sciences; (2) Sociology; (3) Policy; and (4) Economics. The Physical Science group investigated the current biological and geological conditions at Mosquito Point in order to determine the historical and current factors responsible for the erosion and the potential impacts that any solution would have on the ecosystem. Concurrently, the Sociology group performed a study to ascertain the demographic composition of the community residents and property owners as well as their concerns about and desired solutions to the beach erosion. The Policy group determined the relevant regulations that dealt with shoreline management and protection and the guidelines for any recommended beach erosion mitigation option. Finally, the Economics group compiled information on the range of Best Management Practices (BMPs) available and an economic viability (e.g., cost-benefit) analysis. This report summarizes the findings of each group to provide recommendations for a best course of action for Ms. Price s consideration given the existing conditions and her stated wishes to develop a natural solution that promotes environmental conservation and her strong concern for the other property owners. 1.1 STUDY AREA Mosquito Point, Virginia is located approximately 4.8 km (3.0 mi) from the mouth of the Rappahannock River and on the north shore of the river in Lancaster County, Virginia. The Point is situated on the Northern Neck near White Stone, Virginia and covers approximately 0.08 km2 (0.03 mi2/19.8 acres; Figure 1). Sandy beaches dominate the higher energy, southwestern side of Mosquito Point, (Figures 1 and 2). Figure 1. Aerial photo of Mosquito Point, Lancaster County, Virginia. Mosquito Point is located at the mouth of the Rappahannock River near the Chesapeake Bay. The inset at the bottom left shows an enlarged view of the study area. Image source: NASA and Google Earth (inset). 2

6 Figure 2. Oblique aerial photo showing various beaches and beach features located at and in proximity to The Point. Note the abundant sediment and subaqueous bedforms (dunes) offshore of The Point. Photograph taken by Michael Fenster, November 28, Most properties at the eastern end of the peninsula are fortified with rip-rap boulders and groins (Figure 3). Farther up river from The Property is a protruding sand feature which we have called The Horn, 1 and an exposed bluff containing the Pleistocene-aged Shirley Formation (Mixon et al. 1989). Ms. Price s property consists of an undeveloped, 1.48 acre parcel ( The Property ), located on the southern portion of The Point (Figure 2). Geologically, Mosquito Point is dominated by the Shirley Formation which is thought to have been deposited approximately 184,000 ± 20,000 years ago (Mixon et al., 1989). This formation is characterized by 24.3 m (80 ft) of light to dark gray, bluish-gray and brown gravel, sand,, silt, clay and peat (Figure 4). Beds within the Shirley Formation, from bottom to top (oldest to youngest), include a lower pebble to boulder sand bed, a fine-to-coarse sand bed interbedded with organically-rich peat and clayey silt, and a third bed consisting of medium to thickbedded, clayey and sandy silt and silty clay. At the lower James River and Rappahannock River at Mosquito Point lower beds consist of silty, fine sand and sandy silt containing mollusk fossils (Figure 4). 1 The term Horn originates from beach formations called cusps and horns. Cusps are the embayed portions of the beach in the wave breaker zone and horns are the protruding portions of the beach. Together, beach cusps and horns create an arc-like pattern along a beach. While these patterns extend along the shore in a regular, relatively symmetrical pattern, the Horn at Mosquito Point is an isolated feature and resembles others found along the Bay such as Cove Point, Maryland along the upper and western shores of the Chesapeake Bay. 3

7 Figure 3. Oblique aerial photo of The Point showing various shore protection methods used by current residents and property owners. The Property is located upstream from a rip rap revetment. Photo by M. Fenster. Figure 4. Photograph of the bluff upstream of Mosquito Point (left) and lowest (oldest) bed found in the Shirley Formation on the bluff. This bed consist of silty, fine sand and mollusk fossils. Photos by RMC students. 4

8 CHAPTER 2. PHYSICAL SCIENCE ANALYSIS 2.1 INTRODUCTION Beach erosion and the associated landward migration of the shoreline (the intersection of land and water) are responses to a suite of dynamic processes that produce currents capable of picking up sand grains and moving them from a site of erosion to another site of deposition. The currents that redistribute beach sand originate from a combination of processes that develop over a variety of time and space scales. These processes most often include wave action, tides, density differences in the water, and interactions among these processes and between these processes and coasts. In addition, elevation of the water surface by long-term processes such as sea-level rise or short-term processes such as storm surge can enable those processes to reach higher elevations and consequently, increase the vulnerability of coasts to erosion. However, it should be noted that beaches can migrate landward while conserving the volume of sediment contained in the beach. Under these conditions, coastal systems adjust to the driving forces dynamically while maintaining a characteristic geometry that is unique to a particular coast. In developing an erosion management plan, the Physical Science (PS) group sought to document how physical processes control beach morphology (shape) changes at Mosquito Point. Specifically, the PS group characterized the wave climate, sediment transport direction and rate, shoreline migration rate, and the morphological changes that occurred to the beach and the nearshore bathymetry (i.e., the lay of the land under the water) at Mosquito Point in order to understand the shoreline dynamics and causes of erosion in the study area. Erosion management strategies also depend on the biological composition of a coastal ecosystem. Many shoreline management practices include the use of living organisms, such as beach grasses or oysters, which live in habitats characterized by specific and indigenous biotic and abiotic factors. To assess the efficacy of these management solutions, the PS group characterized the water quality and biological community at Mosquito Point in order to determine 1) potential impacts that a given management solution would have on the biological community and 2) what living organisms would survive given the current physical conditions. Coastal engineering structures that armor shorelines can accelerate erosion of beaches and the submerged (subaqueous) portion of the beach profile. For example, shore parallel structures such as seawalls and revetments often require wing walls or tie-ins to adjacent lands to prevent wave erosion at the ends of the walls (called flanking). Bush et al. (1996) discuss how wing walls and tie-ins only temporarily solve the problem as erosion will continue beyond each successive flank. Consequently, beaches can experience both natural erosion as well as having the added anthropogenic effects. 2.2 SHORELINE CHANGE Analyzing shoreline positions over a number of years using aerial photographs can give an indication of erosion or accretion trends in beach width and shoreline position. Aerial (rectified) orthophotographs for the study area for the years 1937, 1959, 1982, 1994 and 2002 were obtained from Hardaway et al. (2006) and were used to determine shoreline trends along Mosquito Point. Digitizing these shorelines into a Geographical Information System (GIS) allowed for analysis of shoreline position at various locations at Mosquito Point over a 65 year period (Figure 5). To calculate rate of change, we used linear regression rates through the shoreline positions for the years listed above at fixed points along a landward baseline (Figure 5). A positive rate of change indicates accretion along the shore (seaward shoreline migration), while a negative rate indicates erosion (landward shoreline migration). We focused our analysis at the end of the Mosquito Point near The Property. 5

9 Figure 5. Map of Mosquito Point s shorelines for the years 1937, 1959, 1982, 1994, and Included is also a baseline of transect points for comparison of shoreline distances. Considerable change can be seen in the shoreline around the end of The Point. From Hardaway et al. (2006) Erosion Prevention at Mosquito Point 6

10 The results from this analysis show that the upstream migration of the Horn from has strongly influenced shoreline migration trends and associated beach changes during this time period (Figure 5). Located at the tip of Mosquito Point in 1937, The Horn moved through The Property and continues to move upriver. Beaches are wide when the Horn is present and narrow with its upstream migration (Figures 5 and 6). Hardaway et al. (2006) give average shoreline rates of change for the reach shown in Figure 5 of -0.1 m/year (-0.3 ft/year). However, the results from individual transects along this reach show substantial variation to this longterm, Point-wide rate-of-change. For example, the results from transect (5600) located near the east end of The Property (near the adjacent revetment) are shown in Figure 7 (location of Transect 5600 is shown in Figure 5). While the linear regression gives an average long-term ( ) accretion rate of +2.9 m/year (+9.5 ft/year), an apparent reversal in the direction of shoreline migration toward the land (erosion) of -7.0 m/yr (-23.0 ft/year) occurred in the mid-1980s. Along the western end of The Property, near The Horn, erosion rates increased from m/year (-16.4 ft/year) from 1982 to 1994 to m/year (-39.4 ft/year) from 1994 to A recent aerial map of the shoreline would enable the most recent ( ) trends to be determined. However, anecdotal evidence indicates that the erosion trend has continued or accelerated since the last date of aerial photography (Figure 8). The movement of The Horn has created a pocket beach along The Property which is a small crescentic, concave (toward the river, bay, or sea) beach (in plan view) situated between two headlands. In this case, the headlands are the immobile revetments to the east and the Horn to the west. While pocket beaches are characteristically stable to accretionary, the migration of the Horn upriver prohibits stabilization of the beach along the Property. However, it is possible that, once The Horn moves upriver and no longer influences The Property, the shoreline will stabilize (assuming no other natural or anthropogenic changes occur). Figure 6. Photograph from the 1950s showing The Horn near the end of The Point. Photograph supplied by John Roberts. 7

11 . Figure 7. Shoreline change measurements from one transect located near the east end of The Property, close to the revetment on the Vose s property. The change in distance from a fixed point shows a recent trend toward landward migration beginning in the early 1980s. Figure 8. Recent photographs of The Property showing erosion, looking to the west (left photo) and to the east (right photo). Photographs supplied by William Vose on March 4,

12 2.3 BEACH PROFILING To develop a baseline dataset that could be used to examine changes in beach morphology, beach profiles were taken using the Emery (1961) Method (named after the oceanographer who developed the method, K.O. Emery) at eight transect locations. Profiles were obtained along seven transects within The Property and on the western edge of the Horn (Figure 9). Measurements were made along each transect from a fixed reference stake every 0.5 or 1.0 meter (horizontal distance) depending on the rate of change in elevation to the water s edge. The water s edge was reached at each transect on the rising tide on March 19, Figure 9. Beach profile transect locations taken at Mosquito Point in the vicinity of The Property on March 19, Image source: Google Earth. The beach profiles from this survey date show a well-developed foreshore and irregular backshore on the eastern transects (Figure 10). To the west, the foreshore shows a nearly vertical erosion scarp and a flat backshore. This area is located in on the eastern edge of The Horn and indicates that The Horn is eroding along this edge. The steep foreshore on the eastern transects (RMC-1, 2, and 3) indicates erosive conditions prevail at these locations as well. 9

13 Figure 10. Beach profiles from Mosquito Point in the vicinity of The Property. Transect 1 = east; Transect 6 = west. The dotted line represents sea level near low tide on March 19, Height (vertical axis) = elevation relative to uncorrected sea level; Length (horizontal axis) = distance from baseline. 10

14 2.4 SEDIMENT ANALYSIS A grain size analysis of the beaches at Mosquito Point was conducted: (1) to determine the source(s) of sediment to The Point; (2) as a proxy for determining the energy distribution and direction of longshore transport along The Point s beaches; (3) to predict the potential for erosion and transport of sediment given various current velocities (i.e., coastal processes); and (4) to aid in providing recommendations for a solution to the erosion problem at The Point. Sediment samples were collected along nine transects that extended along the Rappahannock River side of Mosquito Point (Figure 11). The seven easternmost transects corresponded with the beach profile transect locations discussed above. Samples were collected 3 m offshore of the shoreline, one meter landward of the shoreline, and from the backshore (landward of a visible berm). Sand samples were also collected from three beds (layers) on the bluff face upriver of the beach (Figure 12). Figure 11. Sediment sample locations at Mosquito Point in the vicinity of The Property. Image source: Google Earth. Samples were processed in the laboratory using a Tyler Ro-Tap mechanical shaking device using sieves capable of determining gravel, sand, and mud percents by weight as well as the distribution of sands into very coarse (1-2 mm in diameter), coarse (0.5 mm - 1 mm), medium (0.25 mm - 0.5mm), fine (0.125 mm mm), and very fine (0.125 mm mm) mud (silt and clay) collected in a pan <0.063 mm. Weight percents on each sieve were 11

15 analyzed with Gradistat software in order to determine the mean grain size and variability of each sample (sorting). Upper layer Middle layer Lower layer Figure 12. Bluff located upriver of Mosquito Point. Layers where sediment samples were taken are labeled. Photo by RMC students. Nearly all beaches experience the transport of sediment parallel to the shoreline i.e., longshore transport as the uprush (up the beach) and backwash (down the beach) of waves move sand in a net direction. Changes in sediment grain sizes along a stretch of shore can serve as a proxy for determining the net longshore transport direction. Typically, grain sizes will become finer in the direction of transport. Consequently, the distribution of mean grain sizes along the Mosquito Point shore provided one mechanism for determining the longshore transport direction. The results from the grain size analysis showed that mean grain sizes of the foreshore consisted primarily of coarse- to very coarse-grained sand (except for site 9 closest to the bluff which was fine sand), were coarsergrained than the backshore (medium- and coarse-grained sand) at all sample sites (except at sites 1 and 9), and 12

16 generally finer-grained than the offshore (coarse- and very coarse-grained sand) at all sample sites (except at sites 4 and 9) (Figure 13, Table 1). Figure 13. Mean grain sizes and sorting (± 1 standard deviation = error bars) of the foreshore, backshore, and offshore samples for each transect (dark circles) compared to bluff mean grain sizes and sorting Table 1: Mean grain sizes and standard deviations of Mosquito Point sediment samples. See Figure 11 for sample locations. Site Backshore Mean (mm) Backshore ± 1 s.d. (mm) Foreshore Mean (mm) Foreshore ± 1 s.d. (mm) Offshore Mean (mm) Offshore ± 1 s.d. (mm) Bluff Upper Bluff Middle Bluff Lower

17 The grain size results also show that no trend in mean grain size existed along the shore. This result suggests that localized processes control the grain size distributions on the beach as opposed to more regional or broad processes. For example, the lower beds of the bluff to the west most likely provide finer-grained sediment to the beach in proximity to the bluff or lower wave energies reach this region of The Horn. However, the fine-grained sediments have a low residence time on the beach once exposed to waves, tides, and river flow and do not get deposited down river (to the east). Near the eastern boundary of The Property, the backshore sands coarsen possibly due to higher wave energies refracting around the adjacent revetment. The bluff mean grain sizes are highly variable depending on the bed and range from very coarse-grained on the upper bed to coarse sand in the middle bed and fine sand on the lower bed. This upward coarsening sequence typically indicates a sea-level fall (regression) as these sediments were deposited during the Pleistocene Epoch 184,000 ± 20,000 years ago. In any case, the variable sediment sizes available at the bluff most likely provide a source of sediment to the beaches and offshore region of Mosquito Point. Determining the mean sediment grain sizes along Mosquito Point is an integral part in identifying an erosion control solution that would involve the deposition of sediment from a borrow site (e.g., beach nourishment, Living Shoreline). Compatible sediment from another source requires matching the sediment grain size that exists on a site naturally (i.e., in equilibrium with existing conditions, processes, and energies). Additionally, given that the mean grain size is indicative of wave energy, sediment size analyses allowed us to determine the threshold orbital velocity of waves that erode sand from the beach at Mosquito Point. The threshold orbital velocity (cm/s) occurring at The Point was found using a standard nomogram (Komar and Miller 1973) for a representative wave period (time it takes for successive wave crests to pass a stationary point) using the grand mean grain size for The Point (Figure 14). Wave buoy data at Stingray Point indicate that wave periods at The Point average approximately 2.5 seconds. The grand mean grain size for Mosquito Point was 0.51 mm. Given this wave period and grain size, orbital wave velocities of 20 cm/sec are indicative of The Point. Figure 14. Predicted orbital wave needed to transport a grain of sediment of a given size. The red line shows the conditions at The Point (i.e., mean grain size = 0.51 mm, wave period = 2.5 sec). From Komar and Miller (1973). 14

18 The Hjulstrom (1935) diagram also uses fluid velocities and grain size information to predict whether sediment at a given location will be eroded, transported, or deposited (Figure 15). Mosquito Point s average grain size of 0.51 mm requires a minimum current of 10 cm/s to transport sediments at The Property. Given that the nomogram in Figure 14 predicts that orbital wave velocities at the Property are 20 cm/s, we would expect average conditions at The Point to produce longshore transport of sediment on a regular basis. Figure 15. Hjulstrom (1935) curve showing how fluid velocity affects the transport of sediment given grain size. This chart shows that with The Point s average grain size of 0.51 mm and average fluid velocity of 20 cm/sec, that sediment transport will occur, causing erosion. Source: geology.uprm.edu/morelock/transport 2.5 WAVE DYNAMICS In order to quantify wave dynamics, wave data were obtained from a data collection buoy that is part of the National Oceanic and Atmospheric Administration s (NOAA) Chesapeake Bay Interpretative Buoy System (buoybay.org/site/public/). The buoy used for this study was selected because of its proximity to Mosquito Point and is located east southeast of Stingray Point and between the mouths of the Rappahannock and Piankatank Rivers (Station 44058; Figure 16). The available historical data spanned an approximately eight month period from 19 July 2008 to 31 March Given that wind direction determines the direction of wave approach, we used the buoy s wind direction as a proxy for wave direction. The buoy obtained three wind readings per hour and one wave height reading per hour during this period for a total 7,811 wave height data points. The buoy data indicate that, during this eight month period, waves averaged 0.25 m (0.82 ft) in height and 15

19 came to Stingray Point predominantly from the northeast (40-70 from north) and south ( from north) (Figures 16 and 17). The paucity of waves from the southwest and west is caused by the smaller fetch (the distance over which wind blows to create waves) as the buoy lies in the lee of the Middle Peninsula (land between the Rappahannock and York Rivers). The maximum wave height occurred on March 2, 2009 and was 1.15 m (3.77 ft) and originated from the northeast (41 ). Figure 16. Location of wave buoy data at Stingray Point relative to Mosquito Point (in red box). Image source: Google Earth. Summer conditions were simulated by isolating the buoy data for August, 2008 and winter conditions using March, 2009 data. The August data show that wave approach is highly variable and comes from northeast to south ( from north) during the summer and larger waves occurred less frequently (Figure 18). However, given the east-west orientation of the Rappahannock River channel, these waves have the potential to reach The Point without refracting around shallow water or headlands. Winter waves mimic those of the entire study period with northeast and south prevailing wave approach directions (Figure 19). 16

20 Figure 17. Wave direction, height and frequency from July 19, 2008 to March 31, Figure 18. Wave direction, height and frequency from August 1, 2008 to August 31, Figure 19. Wave direction, height and frequency from March 1, 2008 to March 31, WAVE REFRACTION MODELING Waves, particularly large storm waves, are thought to be responsible for much of the coastal erosion that occurs to a beach in general and to Mosquito Point in particular. Waves begin to feel the bottom, slow down, and refract as they approach the shore. In general, the depths to the ocean, bay or river bottom (i.e., the bathymetry) control the changes in wave direction especially when waves reach depths less than or equal to 10 meters. The direction in which waves refract around bathymetric contours can either concentrate (increase) or disperse (decrease) wave energy at a particular location. Areas of concentrated wave energy often correspond to locations of higher than usual erosion. To determine the potential for wave energy to concentrate at The Point, we used the standard U.S. Army Corps of Engineers manual wave-crest refraction modeling technique (Shore Protection Manual 1984). This method uses Snell s Law to provide a simple estimate for wave refraction with wave properties predicted by linear wave theory. Snell's Law states that the sine of the angle between the wave crest and the bottom contour is 17

21 proportional to the velocity of wave propagation. Given the wave characteristics and the angle of wave approach relative to the bottom configuration (the bathymetry), changes in wave direction can be determined mathematically by: where is the angle between the wave crest and depth contour at an arbitrary depth, o is the angle between the wave crest and depth contour in deep water, C is the wave celerity (speed) at any depth, and C o is the deepwater wave celerity. The manual (as opposed to computer modeling) wave-crest method uses a template to plot the advance of a wave from point to point as it moves onshore (Figure 20). In short, the template uses Snell s Law to determine the angle of departure of the orthogonal (perpendicular) from a position between the depth contours (midcontour). Figure 20: U.S. Army Corps of Engineers wave refraction template (Shore Protection Manual 1984). Using the wave data from the Stingray Point buoy described in the previous section, we used the two most frequent directional wave approaches, and average wind speeds and wave heights for each direction in the refraction model (Table 2). In addition, we used a westerly wave approach to correspond with the long axis or main channel of the Rappahannock River and three hurricane conditions with different fetches to simulate different wave approaches (Table 2). The period for waves from both directions was found and used to determine deep water wavelength using an Army Corps of Engineers nomogram (Figure 21; Shore Protection Manual 1984). 18

22 Table 2: Wave conditions indicative and potential for approaching Mosquito Point. Maximum sediment grain sizes capable of being transported by the power available in the waves for given directional approaches to Mosquito Point also given. Mosquito Point Location (degrees) Fetch (nautical miles) Percentage of Total Wave Occurrence Wind Velocity (kt) Breaker height m (ft) Orbital Velocity (cm/sec) Maximum Diameter Grain Size Capable for Transport (mm) unlimited 1.9% (1.6) unlimited 29.1% (3.6) unlimited 4.4% (2.8) % (1.4) N/A (11.3) Hurricane 43.0 N/A (16.7) unlimited N/A (14.8) Figure 21. U.S. Army Corps of Engineers nomogram for predicting wave height and period given fetch length, wind duration and wind speed (Shore Protection Manual, 1984). 19

23 Because of its unique position (i.e., shoreline orientation) within the mouth of the Rappahannock River, waves approaching from the two most frequent wave directions (the northeast and southeast) do not directly impact Mosquito Point at the scale at which we modeled wave approach (Figure 22). However, waves propagating from the south and northwest (down the long axis of the river) do make direct contact with The Point and are capable of moving grain sizes of 0.9 mm and 4.5 mm respectively (Table 2). We also expect waves coming from the east (up the long axis of the river) to arrive to Mosquito Point although we did not model this direction of wave approach. In short, the direction of waves that have the potential of causing erosion or accretion are influenced by the position of Mosquito Point relative to the mouth of the Rappahannock River. Existing wave height and wave velocity data enabled us to determine the directional wave energy based on fetch. Wave energy data were then used to calculate the maximum possible sediment grain size which could be moved by offshore transport (Table 2). These results indicate that storm conditions have the potential to transport very large particles - including coarse sand and gravel - at The Point. 20

24 Figure 22. Bathymetric map of the mouth of the Rappahannock River. The modeling results of the refracted wave rays (perpendicular to the wave crest) are shown by black arrows. Note the inability of northeast and southeast originiating waves to strike the beach at Mosquito Point. Bathymetric map from NOAA. Erosion Prevention at Mosquito Point 21

25 2.7 WATER QUALITY Living Shoreline erosion control strategies (or other strategies that utilize vegetation) require an understanding the water quality of an area to help in plant selection and design. Water quality was determined using the Stingray Point buoy. This buoy provided data on dissolved oxygen (DO), turbidity, salinity, and chlorophyll-a from July 2008 to March Average salinity ranged from psu (practical salinity units) with the highest salinity in November and December (Figure 23). Thus, given the average salinity, Mosquito Point qualifies as a saltwater marsh with polyhaline (brackish) conditions. A river is usually characterized as polyhaline when salinity is greater than 18 psu. The high level of salinity in this area is a determining factor for onshore plant selection when considering a Living Shoreline. Dissolved oxygen was lowest from July-October at approximately 7.0 mg/l and highest January and February at 10.0 mg/l (Figure 24). Low dissolved oxygen levels affect the abundance of aquatic life within the river. Turbidity ranged from NTU with peaks of 3.5 NTU in September and January (Figure 25). Turbidity levels affect the abundance of submerged aquatic vegetation and oyster reefs. Increased turbidity levels indicate cloudier water which has the ability of decreasing photolytic activity among submerged aquatic vegetation (SAV). Figure 23. Average salinity (PSU) at Stingray Point, Virginia from July 2008-March

26 Figure 24. Average dissolved oxygen (mg/l) at Stingray Point, Virginia from July 2008-March (NOAA online buoy data) Figure 25. Average turbidity (NTU) from July 2008-March 2009 at Stingray Point, Virginia (NOAA online buoy data) 23

27 Chlorophyll-a was relatively uniform at 3.5 ug/l from July 2008-March 2009 (Figure 26). Chlorophyll-a allows plants to undergo photosynthesis. Increased levels of chlorophyll-a (higher than 11µg/L) would indicate an algal bloom, which has the ability to impair a waterway. Low levels of chlorophyll-a (lower than µg/l) would indicate a limited amount of plankton for the diets of fish and aquatic animals. Figure 26. Average chlorophyll-a (ug/l) concentration from July 2008-March 2009) at Stingray Point, Virginia. (NOAA online buoy data) OYSTER REEFS The parameters analyzed (salinity, dissolved oxygen, turbidity, and chlorophyll-a) are important factors for the restoration of oysters and/or submerged aquatic vegetation (SAV). For example, oysters must have dissolved oxygen levels of at least 3.2 mg/l and grow best in salinities >10 psu. Although Mosquito Point is impaired by DEQ standards, according to our measurements, oyster populations could be supported. However, disease and high bacteria levels may affect the abundance and distribution of oysters along the Rappahannock River. Oyster reefs can be used as breakwaters and offer a long-lasting and environmentally friendly solution to erosion. Public and private organizations, such as NOAA, the Chesapeake Bay Foundation, Virginia Institute of Marine Science, and the Virginia Marine Resources Commission have conducted research on historic oyster reefs in the Bay (Newell 1988, Wickfors and Smolowitz 1995). This information helped us understand where in the Bay oyster reefs could survive and thrive today. Oysters live in shallow saltwater bays in water m (8 to 25 ft) deep, between degrees Fahrenheit, and prefer water salinity to be between psu. This matches well with the water quality measured at Mosquito Point; however, by age 3, 80% of Virginia oysters die of disease (MSX and Dermo). MSX is a parasitic disease that has spread from the invasive Japanese oysters and affects oysters of all ages. While MSX thrives in 24

28 warm salty waters of the middle and lower Bay, many oysters are beginning to show signs of resistance. Dermo is similar to MSX but is typically found in waters with lower salinity. Several restored oyster reefs currently exist in the Mosquito Point area along the mouth of the Rappahannock River (Figure 27). These areas were chosen for restoration because of the historic presence of oyster reefs and are areas with water quality high enough to support benthic life. In 2000 and 2001, six oyster reefs were constructed as part of the Oyster Heritage Program. However, restoration potential was limited because of disease. The Virginia Oyster Heritage Program reef located adjacent to Mosquito point is monitored through the VIMS Molluscan Ecology Oyster Monitoring Program via a sentinel upstream buoy. This buoy also records salinity data which can be compared to the buoy data found off of Stingray Point (Figure 28). For the years , the salinity levels range from psu which corresponds to the data fromt Stingray Point. The creation of an oyster reef is a feasible approach to slowing wave energy on The Point while keeping the area natural and enhancing the local ecosystem. Figure 27. Mouth of the Rappahannock River with Mosquito Point indicated. The red areas note potential oyster reef restoration areas as designated by NOAA. These areas are determined by using historic reef maps and by analyzing ecosystem constraints such as water quality and benthic substrate quality. Triangles denote where completed reef restoration sites lay and a circle notes the sentinel monitoring site. Source: Virginia Institute of Marine Science (web.vims.edu) 25

29 Figure 28. Average daily bottom salinity readings from 2005, 2006, 2007 taken from a survey at the Drumming Ground Reef across the Rappahannock from Mosquito Point. Source: Virginia Institute of Marine Science 26

30 2.8 CONCLUSION: THE BIG PICTURE Wave refraction, sediment grain size, beach profile, aerial photographic analyses, and on site observations revealed that multiple processes affect sediment erosion, transport, and deposition at Mosquito Point. While these processes operate over multiple spatial and temporal scales, ranging from sea-level rise at the broadest scale to very low frequency waves at the finest scale, we focused on those processes most responsible for the presentday conditions at Mosquito Point. These data indicate that downriver sediment transport exists along the south shore of the Northern Neck adjacent to the Rappahannock River. Ample geologic evidence of net longshore transport downriver to the mouth of the Rappahannock River exists. This evidence includes: (1) the presence of sandy deltas extending out of small marshes and ebb-tidal deltas adjacent to inlets that point downstream (Figure 29), (2) downstream-pointing spits of sediment forming upstream from The Point, (3) sand accretion on the upriver side of shore-protection structures (Figure 30), and (4) sandy bedforms located just offshore of the beach and upstream from The Point that have crests oriented obliquely to the shoreline (Figures 31 and 32). These obliquely-oriented submerged dunes provide evidence that longshore sand transport the slow process of sand migrating in one direction (in this case, downstream) is occurring. Farther upstream, near the Route 3 bridge (Mary Ball Road ), the submerged sand bars are oriented parallel to the shoreline and indicate that waves have a greater influence over the natural sand transport system and favor onshore-offshore sand migration (Figures 31 and 32). This downstream net direction of sediment transport counter-intuitively has enabled the triangular-shaped deposit called The Horn to migrate up the river over time. In fact, shoreline change maps produced from historic aerial photographs by the Virginia Institute of Marine Science show that The Horn originated from a beach located directly on The Point in 1937 (Figure 31, see also Figure 6). Since then, sand has accumulated on the upstream side of The Horn as a result of downstream directed longshore transport, with sand supplied primarily from upstream sources (including the bluffs located approximately 0. 4 km or 0.2 mi upstream of The Point). This protruding horn acts like a natural groin which prevents longshore transport processes from delivering the natural source of sand to the beach downdrift of The Horn and on The Property. Moreover, storm waves emanating from the eastsoutheast focus wave energy on and erode the downstream side of The Horn (Figures 33 and 34). Wave approach from the east-southeast creates a second hot spot of erosion to the east of The Property ((Figures 33 and 34)). Here, wave energy refracts around the west end of the riprap revetment (located downstream of The Property) and erodes loose sand from the beach immediately adjacent to the revetment through a process known as flank erosion (Figure 35). While the revetment may contribute to the erosion on The Property, the general armoring of Mosquito Point has protected The Point from natural erosion-causing processes. These results indicate that both natural and human-induced processes currently modify the beach conditions at The Property. 27

31 Figure 29. Downstream deflected bb-tidal delta on Rappahannock, just upstream from Whitestone Bridge, indicated by blue arrow. Image source: Google Earth. 28

32 Figure 30. Groins on the northern bank of the Rappahannock River, upstream from Mosquito Point. Note accretion of sand and sediment on upriver side, indicated by blue arrow. Figure 31. Subaqueous bed forms (sand dunes) oriented anti-parallel to the shoreline of Mosquito Point. Sand dunes indicated by red arrow. From Hardaway et al. (2006) 29

33 Figure 32 Subaqueous bed forms parallel to shoreline, upstream from Mosquito Point indicating the influence of wave activity on beach dynamics in this area. Image source: Google Earth. 30

34 Figure 33. Mosquito Point as photographed in Blue arrow indicates The Horn. Yellow arrow indicates the location and direction of primary, natural erosion by waves, and red arrow indicates the location and direction of secondary, erosion caused by waves refracted around hardened shoreline. Image source: Google Earth. 31

35 Figure 34. Mosquito Point as photographed in the mid-1990 s. Red arrow indicates direction of erosion and yellow arrow the site of flank erosion. Note the blue lines, tracing visible waves in the photograph, already showing refraction around hardened shoreline (Photo courtesy of William Vose). Figure 35. Cartoon demonstrating the process of wave refraction around a revetment. The wave ray (black arrow) shows the direction in which wave energy moves as a wave refracts around a revetment. Illustration from U.S. Army Corps of Engineers Low Cost Shore Protection Manual. 32

36 CHAPTER 3. SOCIOLOGICAL ANALYSIS 3.1 INTRODUCTION For the past 25 years, the restoration and protection of the Chesapeake Bay have been two important social, political, and economic initiatives in the Mid-Atlantic region. These initiatives have brought about partnerships among local, state, and federal agencies, as well as non-profit organizations, political activist groups, and various agencies all committed to the improvement and preservation of the Chesapeake Bay (Jantz and Goetz 2007). However, progress made through shifting policies and improving management practices is frequently jeopardized and halted by the increasing population and development within the watershed. Between 1990 and 2000, urban development grew as much as 60%, which in turn has increased sediment and toxic pollution (Jantz and Goetz 2007). In order to solve any problems throughout the Chesapeake Bay, one must first understand the complexity and diversity associated with Bay restoration and protection issues. A variety of factors influence land use ethics, including economic cost/benefit, personal ethics and desires, and community vision. Recently, there has been a growing trend towards multi-disciplinary collaboration on issues related to land use, ecological, and natural resource management (Houde 2007). Given the complexity of this issue, our objectives included obtaining answers to questions regarding land use preferences from our client and the group of property owners at Mosquito Point. Our primary objective was to advise Ms. Betty Price regarding the best practices to mitigate the erosion problem at Mosquito Point, while involving the appropriate property owners in the decision-making process. Again, the goal of this report is to provide a best course of action for Ms. Price s consideration given the existing conditions and her stated wishes to develop a natural solution that promotes environmental conservation and her strong concern for the other property owners. 3.2 SURVEY METHODS We conducted a cross-sectional study involving making observations on a certain population at one point in time, rather than over an extended period of time (Babbie 2007). We designed two different surveys to assess the demographics, opinions, and property information from the property owners and residents at The Point. The first survey included questions that would help us obtain information about the demographics of the area and their opinions as to what should be done with The Property. A second questionnaire was designed to give us more information about the methods used by the individual Property owners for erosion control. In order to distribute our surveys, we used a non-probability sampling method (as opposed to a random selection), which involved all stakeholders (Babbie 2007). The small population of only 26 properties at Mosquito Point required us to use purposive sampling, which is also known as judgmental sampling, rather than doing a random sample. One of the drawbacks to purposive sampling is that it does not necessarily represent a meaningful population. However, because of the small population, we were able to survey each individual, which benefitted our analysis (Babbie 2007). Our first distribution of the surveys was conducted by ing 24 of the 29 Property owners who listed an address on The Property Owners Association address book. We also sent hard copies through the mail to the 26 residents who provided a home address as a second distribution method. Between these two distribution methods 100% distribution was achieved. The mail distribution included a cover letter explaining the purpose of our study, the two surveys, and a business reply envelope so that the respondents would not have to pay postage. 33

37 3.3 COMMUNITY INVOLVEMENT AND GRANT RESEARCH METHODS As per a local homeowners request (Mr. Ralph Crosby), we solicited the aid and involvement of the nearby Christchurch School faculty and students (approximately 15 miles from Mosquito Point). In particular, we worked with Dr. Dean Goodwin and his Environmental Science and Marine Science classes. To this end, we gave several presentations to his classes and collaborated on potential involvement for Christchurch. In hopes of furthering this relationship, we researched educational grants focused on environmental sciences and project-based teaching methods through the Commonwealth of Virginia and foundations throughout the Chesapeake Bay. We also researched grants for Living Shoreline implementation for municipalities, private non-profit organizations, and homeowners associations. Initial attempts to include environmental and marine science students from Christchurch School proved successful, and we established a foundation for future relations between Christchurch and Randolph-Macon. While students and faculty seemed enthusiastic to join in field research, the limited timeframe and significant physical distance between institutions made collaboration difficult. Perhaps the most applicable grant for Christchurch is the Virginia Naturally Classroom grant, dedicated to K-12 schools. The Chesapeake Bay Trust Living Shorelines Initiative also provides funding to non-profit organizations, community associations, academic institutions, and state and local governments in the Maryland, Virginia, and Washington, D.C. areas for Living Shoreline implementation purposes (Appendix I). 3.4 SURVEY AND DATA ANALYSIS Thirteen of 26 property owners on Mosquito Point responded to two surveys for a 50% response rate. Most property owners reside at Mosquito Point permanently (76.9%) as opposed to utilizing their property as a summer home, weekend getaway, or rental property (23.1%). Additional data obtained from these surveys indicate that the population at Mosquito Point consists predominately of a well-established, residential, middle- to uppermiddle class community. With regard to The Property, 53.8% of the respondents stated that they are strongly concerned about the future of The Property, while 15.4% stated that they were not at all concerned. Respondents also noted that they would prefer to conserve The Property in its natural state (76.9%); this preference was supported by 46.7% of respondents who were opposed to having a research facility or residential development on The Property. WHAT RESIDENTS WOULD LIKE DONE The open-ended portions of the questionnaire provided an opportunity for residents to express their concerns as well as their preferred options for The Property. When asked how an erosion management structure on The Property would affect their properties aesthetically and financially, six of 13 respondents stated that a structure would be beneficial or welcome (Figure 36). Residents stated that erosion prevention structures would help to control the erosion on the properties of Mosquito Point, as well as to preserve and provide beach access. The overall vision of the respondents for The Point included erosion control to keep The Point from washing away (38.5%) or residential development (23.1%). Others stated that it should be left unused (30.8%) or made into a park (7.7%). 34

38 Figure 36. Results from the survey distributed to Mosquito Point property owners. Our survey also allowed us to gather a timeline of the construction projects that have occurred at The Point to control erosion. All five existing structures were put into place during the 1980s except for one structure which was installed c Four of the five structures reported include riprap revetments and three of the five include groins. Of the four assessments that were conducted, two had consulted with the Virginia Institute of Marine Science. All of the structures were established to prevent erosion and prevent further property damage. 3.5 CONCLUSION Survey responses indicated that Mosquito Point property owners tend to be upper-middle class professionals and retirees. While most respondents favored conservation, there was also a desire for protection of personal investments and neighborhood quality of life. Neighbors were also concerned with beach access as it is common to all property owners. Any action taken with The Property in question would ideally protect the financial investments of adjacent property owners, conserve the land in question and protect natural habitat on The Point, and finally retain access to beachfront areas for neighbors at Mosquito Point. 35

39 CHAPTER 4. POLICY ANALYSIS 4.1 INTRODUCTION Governing laws of the Chesapeake Bay at the federal, state, and local level must be consulted when approaching shoreline erosion issues as they guide one through the mitigation process. Typically, such laws follow a trickledown effect from the federal level to the local level. National policies tend to be broad, while state and local policies include more specific regulations and recommendations that must meet or exceed federal standards. While these policies must be consulted, it is also important to research the goals and objectives for a locality in order to understand its preferred methods. The following policies and regulations demonstrate the trickle-down effect from federal laws to the laws and preferred methods for the Lancaster County coastline. 4.2 FEDERAL POLICIES COASTAL ZONE MANAGEMENT ACT The Coastal Zone Management Act (CZMA) is the congressional plan for managing America's coasts, which created a partnership between the National Oceanic and Atmospheric Administration (NOAA) and the various coastal states. The federal CZMA requires the state coastal management programs to produce procedures for public participation in, and intergovernmental coordination of program development and implementation. Further, 1456 of the CZMA specifically establishes Coastal and Estuarine Land Conservation Program. This program protects important coastal and estuarine areas that have significant conservation, recreation, ecological, historical, or aesthetic values, or that are threatened by conversion from their natural or recreational state to other uses (Chapter 1456 CZMA). Overall the CZMA policies involved require states to adopt their own program for coastal zone management to receive federal funding. Virginia has its own CZMA, which is known as the Virginia Coastal Zone Management Act (VACZMA). CHESAPEAKE BAY PROGRAM The Chesapeake Bay was the first estuary targeted by Congress for restoration and protection in the United States. The Chesapeake Bay Program was created in 1983 as a partnership between Maryland, Pennsylvania, Virginia, Washington DC, the Chesapeake Bay Commission (a tri-state legislative body), the Environmental Protection Agency, and citizen advisory groups. In 1987, the Chesapeake Bay Program office was created by the Environmental Protection Agency (EPA) and authorized by the Clean Water Act. Through a series of Chesapeake Bay agreements, the participants in the program set forth goals to restore the Bay by reducing nutrient waste in tributaries and evaluating the Basinwide Toxics Reduction Strategy to understand the effects of toxins on the Bay. In 1994, 25 different federal agencies and departments signed the Agreement of Federal Agencies on Ecosystem Management in the Chesapeake Bay to delineate responsibilities of different federal agencies to carry out the goals of the program (Chesapeake Bay Program). The most recent agreement, the Chesapeake 2000, set forth the steps to be taken to protect the Bay for the following decade. The program is implemented at the state level with 36

40 Virginia s Chesapeake Bay Preservation Act (CBPA), emphasizing the use of Best Management Practices (BMPs) for river and tidal shoreline protection. ENDANGERED SPECIES ACT The Endangered Species Act (ESA) was passed in 1973 by Congress. The ESA is dedicated to the conservation of threatened and endangered animals and plants and their habitats. The United States Fish and Wildlife Service (USFWS), along with the Department of the Interior (DOI), maintain a list of more than six hundred endangered species. The ESA can influence the permitting process for erosion protection structures through regulations of development and location as well as procedures specific to species classification. The Northeastern Tiger Beetle has emerged as a primary concern for the Mosquito Point area, due to its historic presence in Lancaster County. Recent local permitting processes involving the Tiger Beetle have caused the ESA to play a role in determining erosion prevention strategies for Mosquito Point. 4.3 State Policies Virginia requires minimum standards, and provides more comprehensive planning for counties with higher standards. Virginia has instituted several agencies, commissions and boards in order to provide quality management and execution of these laws and regulations. Virginia agencies, such as the Department of Environmental Quality (DEQ), are involved in a variety of environmental issues including air, water, and waste issues. The DEQ implements programs and manages and enforces federal, state, and local policies and regulations. One of their most diverse programs is the Virginia Coastal Zone Management Program (VACZMP) under the Virginia Coastal Zone Management Act (VACZMA). The DEQ coordinates with several organizations, including the Department of Conservation and Recreation (DCR), the Department of Game and Inland Fisheries (DGIF), the Department of Health (DOH), the Marine Resource Commission (MRC), Wetlands Board, and local government. All of these organizations play a role in Virginia Coastal Policy, through grants, aid, or education. VIRGINIA COASTAL ZONE MANAGEMENT PROGRAM The VACZMP protects our coastal zones, tidal and non-tidal wetlands, fisheries, subaqueous lands, dunes and beaches, point source air pollution, point source water pollution, non-point source water pollution, and shoreline sanitation. The DEQ implements this program and regulates it through 13 planning districts - Mosquito Point falls under the Northern Neck Planning District Commission (PDC). The program supports each coastal PDC with an annual technical assistance grant. Each PDC offers sponsorship for a variety of regional and local coastal resource management projects. With this support, Virginia's coastal PDCs have been instrumental in the planning and implementation of many other key environmental programs, including the CBPA, Virginia's Tributary Strategy Program, wetlands protection programs, erosion and sediment control programs, stormwater management, Virginia's Ground Water Management Program, and watershed planning. The VACZMP coordinates efforts and funding to help protect and restore our native oyster populations by providing habitat, improving water quality, and restoring seagrass growth. The Virginia Oyster Program was initiated by the VACZMP in partnership with the Virginia Institute of Marine Sciences (VIMS), the Chesapeake Bay Foundation (CBF), MRC, Oyster Reef Keepers, NOAA, and the Chesapeake Bay Office. Virginia s Coastal and Estuarine Land Conservation Program (VCELCP), established through the VACZMA, provides a base of conservation effort from the state, in the form of erosion protection advocacy. The Virginia Erosion and Sediment Control Act (ESCA) of 1973 established regulations controlling erosion, sediment deposition, and runoff for properties, waterways, and other natural resources. The Department of Conservation and Recreation is responsible for implementing the Virginia s Erosion and Sediment Control Program (ESCP), 37

41 according to the Virginia Erosion and Sediment Control Law, Regulations, and Certification Regulations (VESCL&R). The regulations specify minimum standards, which include criteria, techniques and policies that must be followed on all regulated activities. Virginia offers cooperative implementation between the many agencies and departments as well as local entities with the goal of establishing protection for citizens and the protection and conservation of property and its value. Virginia s erosion and soil control policies regulate land disturbance activity and development, such as clearing, grading, excavating, transporting, or filling land. The policies apply to public or private land that can be affected by erosion due to water, wind, and sediment movements into state waters or lands. CHESAPEAKE BAY PRESERVATION ACT (CBPA) The CBPA requires counties in the Tidewater region to designate Resource Protection Areas (RPAs) and Resource Management Areas (RMAs) to protect water quality. RPAs include tidal wetlands, non-tidal wetlands connected by surface flow contiguous to tidal wetlands or tributary streams, tidal shores and other designated lands, and if not properly managed will degrade water quality. A 100-foot buffer is required landward to protect against runoff, and to stabilize soil. There are 3,356 acres of RPAs designated by the Board of Supervisors in Lancaster County. All counties, cities, and towns in the Tidewater region have zoning ordinances, which incorporate measures to protect the quality of state waters. Regulations allow clearing of the 100-foot vegetative buffer for only reasonable water view, water accessibility, and forest management. Buffers with similar effectiveness must be replaced by the property owner after clearing occurs. RMAs include all lands outside of RPAs in Lancaster County s Performance Standards. RMA regulations allow for limited land disturbances during development, and property owners are required to preserve indigenous vegetation, incorporate best management practices, and reduce impervious cover. Any land activity must also comply with the Lancaster County Erosion and Sediment Control Ordinance. Storm water management must follow the goals of Virginia storm water management regulations, and agricultural lands must have soil and water conservation plans. Silvicultural activities are exempt as long as they follow the guidelines set forth by the Virginia Department of Forestry (DOF) in the Forestry Best Management Practices Handbook for Water Quality in Virginia. OTHER REGULATIONS Other state acts and policies include the Virginia Endangered Plant and Insect Act (EPIA), authorized by the Virginia Department of Agriculture and Consumer Services (DACS) to regulate and protect Virginia s endangered plants and insects. The Virginia Endangered Species Act (VAESA), as amended in 1987, regulates endangered or threatened species and prohibits the capture, transportation, processing, sale, or sale attempts of any listed species. The General Assembly has legislation under review to provide greater enforcement through the DEQ and has supported a green land management movement. Increased land stipulation regarding the zoning, permitting, and regulating of development will likely ensue. It will also provide a base for educating citizens and protecting private and state property. 4.4 LOCAL POLICIES OVERVIEW Chapter Four of the Lancaster County Comprehensive Plan describes the goals and policies of Lancaster County for shoreline land management. The County promotes and encourages shoreline protection strategies that address the erosion conditions at specific locations. In low-energy and less-developed areas, the County supports the use 38

42 of soft erosion prevention techniques such as fringe marsh establishment or beach nourishment, while discouraging hard structures such as bulkheads and groins. In high-energy areas, revetments are preferred over bulkheads if the structures sufficiently armor the shore. Furthermore, the County seeks to maintain RPAs established by the CBPA by assessing shoreline protection proposals from housing subdivisions and recommends changes to the RPA to offset proposed impacts. Individual property owners are also encouraged to use natural vegetation in their RPA to enhance water quality and protect the shoreline. Finally, the County promotes cooperative or multi-parcel shoreline protection strategies instead of individual strategies within communities and subdivisions (Lancaster County 2007). SHORELINE PROTECTION PLAN Shoreline property owners in Lancaster County have the opportunity to review the various erosion protection strategies and choose the most appropriate for their circumstances. Heavy armoring with hard structures results in greater economic and environmental costs than soft methods. However, when the extent of erosion is severe, Lancaster County and the Wetlands Board encourage hard structures that will minimize the environmental impact, such as porous revetments that dissipate wave energy, over concrete ones that reflect the energy. Under the Subdivision Ordinance of Lancaster County, newer subdivisions must produce a shoreline management plan to implement shoreline protection methods. Subdivision shoreline management plans, as opposed to individual plans, enable the County to oversee more coordinated efforts on a larger scale. The County promotes this cooperative approach because it provides a uniform and effective solution to erosion issues and shared costs. Vegetative methods are favored by the County because of their reduced costs, increased potential habitat, aesthetic values, and improved biodiversity. Resource Protection Areas under the CBPA can also be maintained with enhancement of vegetative buffers. The County further pursues educational opportunities to inform property owners about erosion issues and shoreline protection alternatives (Lancaster County 2007). ORDINANCES Chapter Two of the Lancaster County Comprehensive Plan outlines several other relevant aspects of local policy in its code of ordinances. The ESC Ordinance exists to protect water quality in the Chesapeake Bay. Any land disturbance that exceeds 2,500 square feet is included under this ordinance, requiring a Zoning Ordinance approved erosion and sediment control plan. The Zoning Ordinance guides various types of land use. The Waterfront Residential Overlay Zone (Article 18 of the Zoning Ordinance) requires all land parcels created after May 11, 1988 and located within 800 feet of tidal waters or wetlands to be at least two acres in size. There must be a 100 foot vegetative buffer, consisting of stable planted area, inward of the high water line and tidal wetlands, a 50 foot buffer inward from wetlands that are not tidal or RPAs, and a 200 foot wide waterfront for new subdivisions. Virginia s CBPA is also included at the local level within the County s Zoning Ordinance, and 3,356 acres of land have been designated as RPAs by the board of supervisors. All remaining lands in the County are considered RMAs. The Flood Plain Overlay (Article 23 of the Zoning Ordinance) includes lands that have been designated by the Federal Emergency Management Agency (FEMA) as part of the 100 year floodplain. Zoning permits are required for all activities within the district, and any development must adhere to the Virginia Uniform Statewide Building Code and the Lancaster County Subdivision Ordinance. To develop in the floodplain, a site plan must be submitted including existing and proposed changes, a 100-year flood elevation, and the elevation of the first floor of any planned residential structures. Finally, the Subdivision Ordinance regulates wastewater disposal, implementation of the CBPA, erosion and sediment control measures, drainage, stormwater management, and flood control within subdivisions in order to protect water quality. The Comprehensive Plan notes that the ordinance fails to promote rural and open space, one of the County s objectives, and it may be subjected to alterations in the near future. At Mosquito Point, any 39

43 type of new development must comply with these ordinances. Given the small scale of erosion protection strategies, the regulations mandating the permitting process, described in detail below, are generally the most relevant. Furthermore, because of the County s emphasis on natural shoreline protection methods, pursuing a natural shoreline is likely to entail a smoother process and greater support from the County itself (Lancaster County 2007). PROCESSES Once a mitigation method has been selected, a permit must be obtained from the County. Lancaster County uses a joint permitting application along with U.S. Army Corps of Engineers, Virginia Department of Environmental Quality (VADEQ) and Virginia Marine Resources Commission (VMRC). This application can be found through the Environmental Codes Compliance Officer of the county. All county officials contact information can be found on the Lancaster County website ( The application must be completed in full and returned to the county offices. It is then sent to VMRC for review. VMRC sends the application back to the county with a review code and a letter regarding the project. A hearing date is then selected, where all concerned parties will discuss the project and a committee will vote. The committee can reject, accept, or request modifications to the project. In the event that modifications are requested, another hearing will be scheduled and the process will start over from there. If the project is rejected, it is possible to appeal to the VMRC. Besides this process, there is a regular fee of $300 associated with obtaining a permit. A key concern when applying for a permit for various projects is the effect that project will have on the habitat of other species. In particular, Lancaster County is concerned with endangered and threatened species. While there is a portion of the permit application that addresses endangered species, Lancaster County also enjoys interaction with Virginia Institute for Marine Science (VIMS). VIMS uses its own research of the project area to predict the potential for endangered or threatened species. They are then able to advise permit applicants on their specific project. Aside from VIMS, the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Services survey and take inventory of the presence of endangered or threatened species. If the project site provides habitat to one of these species the project may need to be modified, or provided with time-of-year restrictions. Also, a special federal permit may be further required. The Rappahannock River and Mosquito Point have historically been known to provide habitat to the Northeastern Beach Tiger Beetle (Cincedela dorsalis dorsalis). This species remains a concern for county officials when reviewing permit applications for the area. Northeastern Beach Tiger Beetles typically survive best in high energy, sandy beach shorelines (Fenster et al. 2006). Data from 1998 indicate that 184 Northeastern Beach Tiger Beetle were found on Mosquito Point (Knisley et al. 1998, Gowan and Knisley 2001) and more recent U.S. Fish and Wildlife surveys showed four adults in 2005 and one adult in 2008 (Knisley pers. comm.) Lancaster County is eager to promote the health of the beach and the safety of Mosquito Point residents. With those concerns in mind, the County encourages shoreline erosion mitigation projects with a low impact on the environment and endangered and threatened species. 40

44 CHAPTER 5. ECONOMIC ANALYSIS 5.1 INTRODUCTION In order to determine the Best Management Practice (BMP) most appropriate for Ms. Betty Price s property, it is important to form a strategy based on an evaluation of the physical, economic, and political conditions present at Mosquito Point. We analyzed physical data concerning wave energy and water quality in order to ascertain the environmental conditions present at The Property. We then applied the information gathered and examined three different categories of erosion prevention in light of the existing conditions: hard structures, soft alternatives and hybrid prevention models. Hard structures, such as groins, revetments and breakwaters are engineered structures typically constructed of concrete, rocks, or wood used to stabilize the shoreline and allow for limited movement of the sediment. Soft erosion mitigation strategies allow for increased sediment movement along the shoreline and often seek to replicate natural processes, such as those created by planting vegetation on shorelines and beach nourishment. Hybrid options are mixtures of hard and soft erosion prevention methods, which a goal of enhancing water quality and habitat formation, while allowing hard structures to absorb or deflect most of the wave energy. 5.2 HARD STRUCTURES The hard structures most appropriate for The Property are groins, breakwaters, and revetments. We chose to focus on these types of hard erosion prevention structures for several reasons, including the fact that several other property owners on The Point have utilized these methods. They are also marketed towards individual residents who wish to protect their property. Finally, these structures can have some additional environmental advantages, such as providing habitat for shellfish. Groins are structures typically installed perpendicular to the shoreline and are intended to block the longshore transport of sand. Most are constructed with stones, or as a freestanding wall to stabilize a stretch of beach against erosion. They can be constructed in series or as a single unit. Groins can be used to establish or build out a preexisting sandy beach, and will absorb or deflect enough of the wave energy to provide a calmer habitat for aquatic plants. Unfortunately, groins can also cause erosion. This occurs because they interrupt longshore transport, which will build out a beach on the updrift side of the groin at the expense of the downdrift side. Groins also require an extensive permitting process and can cost roughly $2,000 per linear foot to install. Revetments consist of layers of stone (usually gneiss, granite or limestone), wood, concrete, or oyster shells set up along the shoreline to help protect and stabilize areas subject to erosion. This durable and long-lasting erosion prevention method is easy to install or repair, and costs between $120 and $170 per linear foot. This structure dissipates wave energy while maintaining the land behind the revetment to prevent erosion. An environmental benefit of revetments is that they can provide habitat for young oysters. A potential downside to a prevention strategy that focuses entirely on revetments is that it prevents the natural migration of wetlands and natural erosion of bluffs, which can eliminate a source of sediment to the beaches. Additionally, revetments tend to have a large footprint on the aquatic bottom because wave energy erodes the sediment foundation of the revetment. In addition, the land shoreward and at the edges of the revetment can be expected to erode. A breakwater is as an offshore structure, typically positioned parallel to the shoreline, which protects the shore from the impact of waves. This occurs because the breakwater dissipates waves before they reach the shore, thus reducing the amount of energy reaching the shore and providing storm protection for the coast. Additionally, beaches can build up behind the breakwater as longshore transport of sand is halted. Breakwaters can be constructed in several different ways, utilizing materials such as rock, wood, oyster shells, and other materials. 41

45 Some problems with breakwaters include the disruption of aquatic habitat through the alteration of wave strength, frequency, and direction. Breakwaters also require extensive permits for implementation, and can cost anywhere from $125 to $250 per linear foot. Breakwaters are not typically constructed by single property owners due to the scale of the project and the effects on neighboring properties. 5.3 SOFT SOLUTIONS The Lancaster County Comprehensive Plan suggests using natural solutions whenever possible when faced with erosion prevention. Given that marshes seem to thrive on the creek side of Mosquito Point, the installation of a marsh seems to be a potential erosion prevention method for the study area. Fifty percent of the wave energy directed at a beach can be dissipated within the first eight feet of marsh. Marshes are resistant to erosion, especially during storms, and are particularly effective when used in conjunction with other erosion prevention methods. Vegetative alternatives are primarily successful on low to moderate wave energy beaches, with erosion rates of less than one foot per year and one to three feet per year respectively. Marshes also provide aquatic habitat and enhance the water quality in an area. The plants cost from $1.25 to $3.00 per plant, including installation costs, and between 50 and 100 plants cover a 200 ft 2 area. We estimate the embayed area fronting The Property at 325 ft (along the beach) x 5-10 ft (across the beach) = 1,625-3,250 ft 2. Consequently, the maximum number of plants The Property would require using these dimensions is plants at a maximum cost of $2,400 - $4,800 at $3.00 each. Soft solutions such as marshes reduce the area of an open beach, which would be a disadvantage for property owners who prefer a recreational beach. Also, marshes are not as effective in areas of high wave energy (more than three feet of erosion per year), and establishment of new marshes takes up to a year. Additional maintenance and replanting may be necessary based on seasonal factors and planting conditions. Beach nourishment is a method that involves borrowing (dredging or truck hauling) sand from one place and placing (often by pumping or dumping) the sand at a new site where a new beach is needed or an existing beach widened. Beach nourishment projects, like most solutions, have advantages and disadvantages. Advantages include the protection of landward structures (e.g., buildings), the creation of new a recreational beach, and minimal residual damage once the artificially placed sand erodes. Disadvantages include the cost given the potential for a short longevity and destruction of habitat for organisms such as invertebrates. Trembanis et al. (1999) show that the average cost per cubic yard (yd 3 ) for U.S. east coast beaches is approximately $5.00 / yd 3 and can reach $15-$20 yd 3 in New England (1999 dollars). Assuming a source of sediment was available, extending the beach 50 ft seaward to a water depth of 6 ft along the beach for 325 ft would require approximately 0.5 x 50 x 6 = (area of a triangle) = 150 ft 2 x 325 ft = 48,750 ft 3 = 1,806 yd 3 x $5.00 gives a total cost of approximately $9,000. This cost most likely does not include mobilization-demobilization of equipment and other factors. 5.4 HYBRID STRUCTURES Hybrid structures combine hard and soft erosion prevention methods in an attempt to protect the shore while maintaining natural conditions with aesthetic benefits. These methods have gained popularity in the last few decades as the long-term advantages of reinforced marshes have become apparent (Berman et al, 2005). Examples of hybrid structures include marsh-toe revetments and sills. Hybrid erosion prevention methods fall into the category of Living Shorelines (Figure 37). A Living Shoreline involves using organic material consisting of aquatic and non-aquatic vegetative root systems to hold back the erosion-prone sediment, preventing habitat from destruction, and improving water quality. 42

46 Sills are semi-continuous structures built to reduce wave action and thereby preserve, enhance, or create a marsh grass fringe for shoreline erosion control (Figure 37). The sill is usually low, and designed to trip or break storm waves before they cascade across the marsh fringe. Thus, they dissipate wave energy before it reaches the upland bank and minimizes marsh toe erosion. They also help to keep marshes healthy and stabilize the shoreline around marshes. Unfortunately, the sill system may reduce the sediment supply to adjacent shores. Also, building a sill system requires encroachment into the bay, usually beyond Normal High Water or the Mean High Water Line. This line constitutes the property limit in most states and complicates the process for obtaining installation permits. Marsh-toe revetments are placed at the toe of a marsh in order to dissipate (lower) the wave energy that reaches the vegetation (Figure 38). These revetments protect the marshes, which in turn stabilize the shoreline. They also promote shellfish growth by providing hard surfaces to which oysters and clams can cling and fisheries development by providing enhanced aquatic habitat. Both environmental benefits play an important economic role in the Chesapeake Bay. According to the Chesapeake Bay Program ( one oyster can filter more than 50 gallons of water per day. In a scientific study, Riisgard (1988) showed that the eastern oyster (Crassostrea virginica) can filter 6.8 liters/hour (1.8 gallons/hour) or liters/day (43.2 gallons/day). Filtering large volumes of water through their gills removes nutrients, suspended sediments and chemical contaminants which, in turn, leads to improving water quality. Marsh-toe revetments have been used successfully in the Chesapeake Bay and other river tributaries and canals, such as Machodock Creek. The installation costs are roughly the same as revetments, and permitting may be required. Figure 37. Hybrid Structures: A Living Shoreline. Rock sill with a marsh restoration project. From: 43

47 Figure 38. Marsh-toe revetment (side view). From: dcm2.enr.state.nc.us/estuarineshoreline/options.html 5.5 RECOMMENDATIONS We recommend that the best course of action for controlling erosion at The Property is to pursue a living shoreline in combination with a nearshore submerged reef breakwater. This approach has ecological and financial benefits for The Property and the surrounding area. Living shoreline management techniques can prevent shoreline erosion while maintaining benefits to wildlife and water quality. Consequently, a living shoreline is a long-term solution to restore and enhance natural beach habitats at Mosquito Point. These benefits are achieved through the strategic implementation of plants, stone, sand fill and other structural and organic materials. The environmental and financial benefits of living shorelines outweigh the negative environmental impacts and minimize costs associated with hard structures (e.g., revetments, bulkheads, etc.). Moreover, this approach adheres to local land use policies. Because The Property is situated within an area of moderate wave energy, the hybrid erosion prevention methods are appropriate as an erosion management strategy. A typical living shoreline would incorporate a succession of plants and natural filters that would be found in undisturbed ecosystems. As recommended by the Chesapeake Bay Foundation, this implementation of a hybrid method would consist of: riparian buffers above the high tide line, native trees and shrubs, including a mix of shrubs at high tide elevation; tidal wetlands, including grasses, rushes, and sedges at mid-tide elevation, and marsh grasses at low tide; oysters, oyster balls and an oyster reef where appropriate 44

48 underwater grasses in shallow water; and coconut-fiber rolls (biologs) We recommend a living shoreline as the preferred solution to the Mosquito Point erosion problem because of its environmental benefits and demonstrated successes throughout the Chesapeake Bay. Many areas in the Chesapeake Bay such as Cabbage Patch Reef (Cape Charles, VA), Smith Island, (Crisfield, MD), and Poquoson Reef, (Newport News, VA) have all experienced success after implementing a living shoreline and/or oyster reefs. Machodock Creek in Westmoreland County, VA has also had success with their living shoreline that includes vegetation behind a low revetment. Another area that has successfully incorporated a living shoreline is Horsehead Wetland in Queen Anne County, MD. Horsehead Wetland has established a system of offshore oyster bars created from stone rubble to decrease wave energy before reaching the shoreline. In fact, several restored oyster reefs exist in the Mosquito Point area along the mouth of the Rappahannock River. These areas were chosen for restoration because of the historic presence of oyster reefs at these locations and water quality high enough to support benthic life. These examples suggest that it is possible to incorporate a living shoreline and oyster reef breakwater at Mosquito Point as an erosion prevention solution (Figure 39). The erosion control devices initially considered, such as revetments, groins, and breakwaters are not the preferred erosion control alternatives for The Property because of their environmental and/or economic disadvantages. Living shorelines - especially those with built-in oyster reefs as breakwaters - address concerns dealing with aesthetic appearance, erosion control, habitat creation, and overall improvement in water quality. Consequently, living shorelines and natural breakwaters (oyster reefs) offer a long-lasting and environmentally friendly solution to the erosion problem at Mosquito Point. Reef Orientation N 500 ft 200 m Figure 39. Recommended orientation for nearshore submerged oyster reef breakwater. Image source: Google Earth. 45