1. Some Types of Coastlines A closer look at: Estuaries, Deltas and Barrier Islands

2. Estuary An estuary is a partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with tidal influences from the sea /ocean

3. Why are estuaries important? They are very productive ecosystems which provide habitats for wildlife To find shelter To find food As breeding grounds

4. Fig 20.22

5. Unique ecosystem: Salt marsh

6. Mangroves

7. Oyster bars

8. Mud flats

9. Horseshoe crab

10. Blue crab

11. Estuary Types (4) 1 Drowned river valley – Chesapeake

12. Ancient river channel is on the east side of the Bay.

13. Other Estuaries Bar-built – Sand bar blocks river Fjord – Flooded Glacial valley Tectonic – Land moved via regional tectonic activity

14. Bar Built Estuary

15. (sand) bar built estuary, Cape Hatteras NC

16. Fjord

18. Greenland fjords from satellite

20. Glaciers (depositional) As huge continental glaciers melt they leave behind sediment called moraines.

22. Tectonic Estuary

23. Baja Peninsula from satellite

24. Deltas Rivers deposit sediment at coast If more fluvial influence than ocean influence Bird’s foot delta If more ocean influence than river influence Arcuate delta FIG. 11.11b

25. Nile River empties into the Mediterranean Sea Arc shaped delta, ocean forces dominates, think longshore transport reshaping the front edge

28. Mississippi Delta

29. Barrier Islands Detached linear islands of sand that run parallel to the shore Backed by a bay, lagoon, marsh Built by waves, wind and tides http://www.virginiaplaces.org/geology/barr ier.html

30. Shape and Size Barrier islands occur in chains Chains are separated by inlets Storms produce inlets Tides keep them open Waves transport sediment that fills them in Width of the island is determined by amount of sediment supply

31. 4000 km barrier islands on east coast and gulf coast

32. New Jersey Barrier Islands

40. http://coastal.er.usgs.gov/hurricanes/denni s2005/photosets-santarosa.html

42. Origin of Barrier Islands At the end of the last Ice Age, sea level was a the edge of the continental shelf. The climate was much colder. Large dunes formed a beach ridge and were the natural shoreline

43. As sea level began to rise, the dunes were breached as the waves washed over them and a lagoon or bay began to fill in behind them. The beach ridge becomes a barrier island backed by a bay or lagoon

44. The barrier system migrates landward across the shelf as sea level continues to rise

45. Rising sea level pushes barrier island landward

50. http://coastal.er.usgs.gov/hurricanes/denni s2005/photosets-santarosa.html

51. Oyster shells exposed here have been found to be 8000 years old. When they were alive this was the sound side of the barrier island

52. Ocean City in Winter

54. . From the period 2014 to 2044 at least 9 million cubic meters of sand will be required to maintain Ocean City beaches.

56. Interesting … There have been 16 sets of barrier islands in the past 2 million years. They come and go with the rise and fall of sea level during ice ages.

59. The Future of Barrier Islands Barrier islands need new sand input to continue to grow and rising sea level to keep the lagoon from filling with sand So, barrier islands may eventually disappear

60. Fig 20.16 Oops, shouldn’t have put the house there (part 13)

61. Cape Hatteras Lighthouse (before)

62. Fig 20.C (after)

63. Hard stabilization Groin and groin field Perpendicular to shore Traps sand between groins Interrupts longshore current Jetty similar Built to protect harbor entrance Sand on upcurrent side

64. Breakwater Parallel to shore Offshore Deposition behind breakwater

65. Seawall Built on beach Parallel to beach Erosion enhanced seaward of wall Seawall destroyed Beach narrowed Fig. 11-25

66. Alternatives to hard stabilization Limit construction near shore Relocate businesses/homes destroyed by wave erosion Beach replenishment

67. End of Chapter 11: The Coast: Beaches and Shoreline Processes