1. Waves, Beaches and Coastal Erosion

2. Tidal forces associated with Moon 1

3. Tidal forces associated with Sun and Moon High tide stays aligned with moon but Earth rotates, yielding 2 high and 2 low tides each day.

4. Tides are cyclical floods Tidal forces associated with Sun and Moon Neap tides: Sun and Moon tides are out of phase Spring tides: Two tides are in phase-- High tide will be higher than usual

5. Tidal Ranges Are Highly Variable: Bay of Fundy--17 m!

6. Tidal Ranges influenced by local conditions and bathymetry Bays tend to focus the water and create larger ranges Organisms are stratified based on tidal zone

7. 2) Sea Level: What and When? Mean sea level is the average height of the sea… Relative to what? When? High or low tide? Measured with tide gauges

8. Sea Level: Changes through time

9. Eustatic Sea Level Changes “Eustatic” refers to changes related to amount of water in the oceans

10. 3) Tidal Flats: exposed mud at low tide

11. 4) Waves and Sediment Transport

12. Wave Velocity- Deep Water

13. Wave Energy Doubling wave height quadruples energy: E w = 0.125  gH 2 L where: E w = energy of wave  = water density (g/cm 3 ; close to 1) g = acceleration of gravity (9.8 m/sec 2 ) H = wave height (m) L = wavelength (m)

15. Passive continental margin Submarine canyons Coastal plain Continental shelf Continental slope Continental rise Continental crust Continental crust Oceanic crust Mantle Deep-sea fan Abyssal plain

16. Path of water particles Longshore current Rip current Path of sand particles 5) Waves approaching the shore at an angle cause a longshore current. Longshore drift results from movement of sand particles by swash and backwash.

17. Sand will move in this direction The beach is a “river of sand”

18. 6)Headlands receive strong wave energy- leads to erosion

21. 7) Rip Currents

23. 8) Sand Supply/Loss

25. Offshore sand bars migrate to beach during summer Winter storms remove beach sand to deeper water Hurricanes result in summer beach sand loss

26. 8) Sand Supply/Loss

27. Engineered Beach Protection Structures

28. 9) Erosion of Gently Sloping Coasts and Barrier Islands

29. Beach migrated 400 m in 60 years

30. Barrier Islands are Geologically Temporary

32. Chandeleur Islands Before (above) and after (below) Hurricane Katrina

33. 10) Sea Cliff Erosion Headlands erode from wave action Creates caves, arches, sea stacks

34. Sea Cave

35. Arches

36. Sea Stacks

39. Sea Cliff Erosion

40. Coastal Erosion