Gly 558. Introduction to Coastal Management. Aeolian Processes and Dunes. Namib Coastal Desert. What Can Dunes Tell Us About the Coastal System?

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1 Gly 558 Introduction to Coastal Management 300m high Namib Coastal Desert GE Crescent dunes Onshore prevailing wind Benguella Current Aeolian Processes and Dunes Linear dunes Fog What Can Dunes Tell Us About the Coastal System? Their presence can provides clues about: Wind direction Sand supply, Storm history (scarps & washovers) Erosion history Sea level change Shoreline stability (with vegetation) Relative age Presence of inlets Man s influence Dune Types and Morphology Along NC coast there are two major types of dunes and several variations. Transverse Parabolic Medanos Sand sheets Slipface Transverse Dunes Parabolic dunes Dune Types and Morphology Parabolic Recurved Dunes and Spit Growth Recurved dune ridge complexes typically develop on the updrift side of migrating inlets. Sand Sheet Caswell Beach,NC Caswell Beach,NC Parabolics Parabolics Parabolics New Topsail Inlet Rich Inlet

2 SC Spits and Recurved Dune Lines Large sand supply at migrating inlets leads to development of a variety of recurved dune complexes. Kiawah Island, SC Kiawah Island Modified Dune Ridges Vegetation has been stripped on some dune ridges (on regressive barriers). Results in remobilization of sand. Vegetation changes due to fires, hurricanes, man s activities (timber for boats & grazing). Remobilization of sand leads to different dune morphology (plan view and height). A Cape Romain B C Complex Parabolics Ilha de Florianópolis SC Moçambique Santinho Ingleses Migrating and arrested parabolics Praia Ingleses, SC, Brazil, SC, Brazil Outer Banks of North Carolina Currituck Banks Bodie Island Oregon Inlet Pea Island Cape Hatteras Hatteras Inlet Ocracoke Inlet Hatteras Island Drum Inlet Portsmouth Island Cape Core Banks Lookout 2

3 Outer Banks, NC (Currituck Spit) Flood Tidal Delta (FTD) Currituck Inlet Parabolics Parabolics/Medanos FTD FTD FTD Parabolic Dune Migration Kitty Hawk Jockey s Ridge Nags Head Area Roanoke Channel Sisters Dunes Wright Brothers Monument Feb 1984 Hatteras Lighthouse / Buxton Area Hatteras Island Buxton Hatteras Island 3

4 Mid 1930s Ocracoke Island Ocracoke Island / Mid 1990s Mid 1960s 1984 Core Banks Core Banks - Cape Lookout, NC New Drum Inlet 1978 Hurricane Gloria (1985) Breaches and Washovers Shackleford Banks Bogue Banks NC - Former Regressive Barrier Bogue Banks is comprised of several regressive barrier segments. Numerous areas of recurved beach/dune ridges testify to presence of former inlets. 4

5 Forested Dune Ridges Maritime forest colonized sequence of high dune ridges Sand Rich Barriers Emerald Isle, NC (Bogue( Banks) Bogue Banks (East View 1975) Browns & Bear Islands Sand Rich Modified Dune/Beach Ridge Barriers Bogue Inlet Inlet Influence and Hurricane Response Hurricane Fran 9/7/96 Onslow Beach Impact of USMC amphibious exercises Loss of dune integrity Overwash & erosion Post Hurricane Fran Oct 1996 AIWW Hurricane Bonnie 8/28/98 5

6 New River Headland Area North Topsail Beach New River AIWW Onslow Beach Browns Inlet Bear Inlet Browns Island Bear Island Sand Rich Barriers New River Inlet N North Topsail Beach Sand Poor Barriers 0 3 KM North Topsail Beach Hurricane Fran (Sept. 5, 96) Topsail Island North Topsail Beach & Surf City 6

7 Topsail Beach Surf City, March 10th, 2001 Headland Pleistocene Barrier System Flood delta Refurbished dune Topsail Beach Chronic Erosion New Topsail Inlet, NC Net Drift 9/99 1/86 9/99 1/86 12/00 1/86 1/87 Lea & Hutaff Islands SE North Carolina North Topsail Beach Sand-Rich Barriers I Cape Lookout Submarine Headland Figure Eight Island N II Wilmington) Wrightsville Beach 15 km Kure Beach Cape Fear Sand-Poor Barriers 12/75 1/86 ONSLOW BAY Subeaerial Headland 8/99 8/00 7

8 Figure Eight Island North End Figure 8 Island 5/20/84 F8I North End Erosion (8/02) Figure Eight Is. Storm Related Damage A Post Hurricane Floyd (9/19/99) Shell Island Wrightsville Beach Figure Eight Island C Shell Island Resort 1986 Oct 98 12/75 8

9 Wrightsville Beach Old Moore s Inlet /98 Masonboro Island Mid Barrier Change 9/80 8/98 Scarped 1980 Grasslands / /1998 Masonboro Island 1/87 1/98 10/98 Atlantic Intracoastal Waterway Lagoon (estuary) Termination Carolina Beach Masonboro Island Carolina Beach Inlet Rip-rap ~ 18 M yd 3 Beach Fill Former Tidal Creek (ca 1900) 9

10 Carolina Beach South View Kure Beach (Post-Hurricane Fran 9/96) Humate SS (Pleistocene) 3/1995 Pleistocene Stump Forest Rip-Rap Cape Fear River Cape Fear (Bald Head Island) Seawall Coquina Outcrop Mainland Riggins Townhouses Kure Beach Beachfill Project Cape Fear Foreland Fort Fisher Shoreline Change Jan 1998 Bald Head Island Oak Island Setting Pleistocene Sandstone /Coquina Long Beach Spit Yaupon Beach Headland Caswell Beach Spit 10

11 Eastern Spit (Caswell Beach) Cape Fear River Western Spit Oak Island (Long Beach) Caswell Spit Yaupon Beach Pleistocene Headland CPL Nuclear Plant Cooling Canal Caswell Spit Cape Fear River Hurricane Floyd (9/99) Beach Nourishment Holden Beach Inlet-Related Erosion 1994 Parabloic Dunes Erosion ranged from m since Holden Beach Erosion 1996 Eroded or Relocated 11

12 Ocean Isle Shallotte Inlet AIWW Oak Island Holden Beach Ebb Channel 19th C shoreline? 150 m erosion Ocean Isle 1996 Cleary 5/01 Ocean Isle & Sunset Beach Sunset Beach Sunset Beach Progradation Little River Inlet (SC/NC) Sunset Bch. Bird Is. Tubbs Inlet Mad Inlet Little River Inlet 1999 Little River Inlet Jetties Waites Is. Mad Inlet Sunset Bch

13 Little River Jetties - Bird Island 1996 Bird Is. Jetty 13