Coasts: Beaches and Shoreline Processes

1. Coasts: Beaches and Shoreline Processes

2. Coastal Processes • Three Main Coastal Zone Processes controls what features we see along the coasts. • Tectonics- 1st order control (i.e., Primary) • Geology/rock type- 2nd order control • Waves and currents- 3rd order control

3. Coastal BedrockRates of erosion and deposition (Trujillo & Thurman, 2005)

4. Tectonics imparts a first order effect on coastal geomorphology • Two major geomorphic types of coastline: • Leading Edge Coasts/ Erosional Coasts • Emergent coasts (uplift) • Trailing Edge Coasts/Depositional Coasts • Submergent coasts (subsidence)

5. Leading Edge Coasts are characterized by erosional features • Sea cliffs • Marine terraces/ wave cut platforms • Sea Caves • Sea Arches • Narrow shelves • Pocket beaches • Sea stacks and headlands • Small drainage basins, low sediment supply • High gradient with coarse sediment • Tectonic uplift

6. Schematic drawing of important erosional features (Garrison, 6th ed., Fig. 12.4a)

7. Wave cut Platforms/Sea Stacks (Garrison, 2005) (Garrison, 6th Ed., Fig. 12.4b-d)

8. Trailing Edge Coasts are characterized by depositional features • Barrier islands • Tidal marshes, estuaries and inlets • Wide shelves • Broad coastal plains • Long continuous beaches • Large drainage basin, high sediment supply • Low gradient with fine sediment • Subsidence

9. Depositional features along a trailing edge coast (Garrison, 6th Ed., Fig. 12.19)

10. Typical Beach Profile (Garrison, 6th Ed., Fig. 12.14)

11. Beach Profiles Summer Winter (Trujillo & Thurman, 2005. Also a similar figure 12.15 in Garrison, 6th Ed.)

12. Longshore CurrentBeach a river of sand (Trujillo & Thurman, 2005)

13. Coastal Cells in Southern California (Garrison, 6th ed., Fig. 12.18b)

14. Coastal Sediment Transport Cells (Garrison, 6th Ed., Fig. 12.18 a and c)

15. Rip Currents (Trujillo & Thurman, 2005)

16. Environmental Aspects of the Coastal Zone • The coastal zone is in a dynamic equilibrium • Therefore most features are ephemeral, both • Natural ephemeral features • Man-made features

17. Natural Ephemeral Features • Tombolos • Spits • Barrier Islands (Garrison, 6th Ed., Fig. 12.19)

18. Man-made features/Construction in the coastal zone • Main reasons for construction in the coastal zone: • Improve navigation • Reduce coastal erosion • Aesthetics

19. Main man-made structures • Jetties/Groins • Breakwaters • Sea Walls/Rip-rap

20. Jetties and Groins (Trujillo & Thurman, 2005)

21. Breakwater Santa Monica, CA (Trujillo & Thurman, 2005)

22. Estuaries • Define an estuary? • A protected coastal body of water with freshwater input at its head and seawater input at its mouth.

23. Origin of Estuaries • Coastal plain estuaries/Drowned river valleys • e.g., Tampa bay; Chesapeake Bay • Fjords/Glaciated U-shaped valley • e.g., Strait of Juan de Fuca, WA; Norway • Bar-built estuaries/Coastal lagoons • e.g., Albemarle and Pamlico Sounds, NC • Tectonic/Fault block estuaries • e.g., San Francisco Bay and Tomales Bay, CA

24. Estuaries classification by origin (Garrison, 6th Ed., Fig. 12.30)

25. Drowned River Valleys (Trujillo & Thurman, 2005)

26. Types of Coral Reef Coasts (Garrison, 6th Ed., Fig. 12.28)

27. Coasts Formed by Biological Activity Types of Coral Reef Coasts

28. Examples of a Fringing Reef and an Atoll (Garrison, 5th Ed., Figs. 12.26 and 12.27)