1. Coastal Process Chapter 9:

2. Wave Dynamics Wave length (L)= Distance between crests, Wave height (H) = Vertical distance between the crest and the trough Wave base = depth below which waves have no effect = ½ * wave length Period (T)= Time taken for two successive waves to pass a point Velocity (V) = L/T

4. Breakers form when the sea-bottom is at a depth less than the wave base Surf Zone = Zone along which breaking waves collapse Swash and backwash = up and down movement of water along the shore line

5. Sydney, Australia Notice the surf zone and also the rip currents

6. Coastal erosion and sand transportation Wave refraction Longshore current and Littoral drift Cliff erosion Groin and Breakwater Groin

10. Sea-stacks

12. Beach

13. Offshore = Farthest out, beyond surf zone Foreshore = surf zone, tidal flat and swash zone Backshore = Inwards from Foreshore upto the coastal dunes Berm

17. Virginia Keys What is the direction of the Longshore Current?

18. Commenced 1970 s $62 million over 10 years, 160 K m 3 of sand 18 million m3 of sand dredged and pumped 200 m wide beach by 1980s

19. Berm Swash Zone Miami Beach

20. Nature of Coast Line Active Margin –Western Coast of USA –Steep Continental Shelf –Narrow beach –Rocky cliffs Passive Margin –East Coast –Wide, gentle beach, sandy offshore islands –Broad Continental Shelf

23. Erosional and Depositional Landforms Erosional: Wave-cut terrace (or platform)= Flat rocky surface beneath the surf zone Sea-stacks = Remnants of sea-cliff left standing in the sea

25. Wave-cut Terrace

26. Coastal Hazards Sea Level Rise Hurricanes, Storm surge Recognition of coastal hazards

32. Coastal Erosion Human modification has accelarated erosion Coastal Engineering structures e.g., sea walls Damming of rivers Subsidence due to withdrawal of groundwater, oil etc

33. Spit Depositional Landforms: Spits = narrow extension of beach formed by longshore current Barrier Island = sandy offshore islands parallel to the shoreline Do you know this place?

34. Safety concerns High elevation (>5 m) above normal high tide Well developed beach dunes between the site and the water-line Overall water level – maximum storm-surge limit Emergent or Submergent coast? Rate of coastal erosion (from USGS and county maps)