1. Class 30 -- The Oceans BEACH PROCESSES
Transport of sediments along shorelines
Human intervention in beach processes

2. Wave fronts and onshore "swash" -- oblique to beach front
"Backswash" perpendicular to beach front

3. Net Result: Longshore transport,
Water and sediment move parallel to the beach front

4. Longshore transport It’s strength depends on wave energy…
Sediment moves rapidly in areas of greater wave energy
Sediment dropped where wave energy is lesser

6. Erosion occurs in areas of strong wave action (headlands)
Longshore transport tends to be away from headlands and toward quieter areas

7. Both sediment and water converge in recessed areas
Sediment collects there (beaches)
Water turns back seaward
Rip currents move water offshore

9. BEACH PROCESSES -- Natural
Beach = temporary accumulation of sediments
Seds come from rivers, headland erosion
Beach dynamics -- continuous sediment movement due to waves and longshore currents.

10. BEACH PROCESSES -- Natural
Most beaches constantly gain and lose sediment
The budget can have a surplus or a deficit

12. Human Impact On Beach/coastal Processes
(1) Dams on rivers
Reduce sediment input to coasts; beaches become “sediment starved”
Longshore transport continues carrying seds
Beaches are eroded

13. Human Impact On Beach/coastal Processes
(2) "Groins" to minimize loss of beach sand
Upwind side: deposition
Downwind side: erosion; beaches starved of their sediment supply

15. (3) Breakwaters to protect harbors
Reduce wave energy --> deposition in harbor
Need frequent dredging
Erosion of downwind beaches- sediment supply cut off

18. Beach dynamics
2 Common themes:
Sediment transport links all beaches, sediment sources, and sediment traps on a coastline
Intervention to address a single demand of society often leads to a chain of unforeseen consequences due to erosion or deposition.