1. CHAPTER 10 The Coast: Beaches and Shoreline Processes S

2. Overview Coastal region constantly changes Coastal region constantly changes Primarily due to waves Primarily due to waves Erosion Erosion Deposition Deposition Many people live in coastal regions Many people live in coastal regions 80% of people in U.S. live within easy access of coast 80% of people in U.S. live within easy access of coast P

3. Coastal Processes Wave Refraction and the Longshore Current Wave Refraction and the Longshore Current Convergence and Divergence of Wave Energy Convergence and Divergence of Wave Energy Sediment Cells Sediment Cells Sediment Budget Sediment Budget Grain Size and Beach Slope Grain Size and Beach Slope P

4. Fig. 10-1 S

5. Fig. 10.3b P

6. Composition of beaches Locally available material Locally available material May be coarse or fine May be coarse or fine Boulders from local cliffs Boulders from local cliffs Sand from rivers Sand from rivers Mud from rivers Mud from rivers Significant biologic material at tropical beaches Significant biologic material at tropical beaches Example, Coral reef material Example, Coral reef material P

7. Longshore current Wave refraction causes water and sand to move parallel to shore Wave refraction causes water and sand to move parallel to shore Zigzag motion in surf zone Zigzag motion in surf zone Longshore current Longshore current Longshore transport Longshore transport P

8. Longshore transport Millions of tons of sediment moved yearly Millions of tons of sediment moved yearly Direction of transport changes due to wave approach Direction of transport changes due to wave approach In general, sediment transported southward along Atlantic and Pacific coasts of U.S. In general, sediment transported southward along Atlantic and Pacific coasts of U.S. S

9. Wave Refraction S

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12. Convergence Divergence S

13. Lower energy, sand settles out S

14. Beach compartments Rivers supply sediment Rivers supply sediment Beach Beach Offshore submarine canyons “drain” sediments from beach Offshore submarine canyons “drain” sediments from beach P

15. Fig. 10.4 S Erosional Coastline

16. Depositional shorelines Primarily deposited by longshore drift Primarily deposited by longshore drift Beach Beach Spit Spit Bay barrier Bay barrier Tombolo Tombolo Barrier island Barrier island Delta Delta Beach compartment Beach compartment Fig. 10.7 S

17. Depositional shorelines Fig. 10.8 S

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19. Fig. 10.12 P

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23. Winter Summer S

24. 10_02a S Summer

25. 10_02b S Winter

26. 10_Ar S

27. 10_26Al P

28. P

30. Changing sea level Local tectonic processes Local tectonic processes Example, Pacific Coast of U.S. and active plate margin Example, Pacific Coast of U.S. and active plate margin Isostatic adjustments Isostatic adjustments Ice-loading Ice-loading Global (eustatic) changes in sea level Global (eustatic) changes in sea level Changes in sea floor spreading rates Changes in sea floor spreading rates Lake buildup or destruction Lake buildup or destruction Ice volume changes Ice volume changes P

31. Eustatic changes in sea level Ice build up (glaciation) Ice build up (glaciation) Ice melting (deglaciation) Ice melting (deglaciation) Thermal contraction and expansion of Thermal contraction and expansion of seawater seawater About 120 m (400 ft) change in sea level About 120 m (400 ft) change in sea level P

32. Fig. 10.15 P

33. Global warming and changing sea level About 0.6 o C (1.1 o F) warmer over last 130 years About 0.6 o C (1.1 o F) warmer over last 130 years Sea level rose 10- 15 cm (4-10 in) over past 100 years Sea level rose 10- 15 cm (4-10 in) over past 100 years If global warming continues, higher sea level If global warming continues, higher sea level Fig. 10.15 P

34. U.S. coasts Erosion or deposition dominates Erosion or deposition dominates Type of bedrock Type of bedrock Tidal range and wave exposure Tidal range and wave exposure Active tectonics Active tectonics Eustatic changes in sea level Eustatic changes in sea level Fig. 10.16 S

35. Alternatives to hard stabilization Construction restrictions Construction restrictions Limit building near shorelines Limit building near shorelines National Flood Insurance Program encouraged construction National Flood Insurance Program encouraged construction Beach replenishment Beach replenishment Sand added to beach/longshore current Sand added to beach/longshore current S

36. Alternatives to hard stabilization Relocation Relocation Move structures rather than protect them in areas of erosion Move structures rather than protect them in areas of erosion Fig. 10B S