GEOL 1 Lecture Notes - Lecture 31: Longshore Drift, Wave Power, Refraction
Jeff Koo
Geol 1
Physical Geology
Spring 2019
4 Units
COASTAL PROCESSES
● Coastal Environments
○ Dynamic environment
■ High energy vs. mass
● Moving water acting on land
○ Shoreline response
■ Erosion, transport and deposition
■ Result: constant change
● Energy in Oceans
○ Wave action
○ Tides
○ Currents
■ From both waves and tides
● Waves in the Ocean
○ Waves result from wind on water’s surface
■ The higher the wave, the more energy it has
● Wave Refraction
○ If waves approach shore at angle other than 90…
● Longshore Drift
○ Refracted waves have some of their energy directed parallel to shore
○ Creates a current along the shore
■ Longshore current
○ Moves sediment along the coast
■ Longshore Drift
● Rip Currents
○ Where wave energy flows back out to sea
○ Incorrectly called “rip tides”
Document Summary
Waves result from wind on water"s surface. The higher the wave, the more energy it has. If waves approach shore at angle other than 90 . Refracted waves have some of their energy directed parallel to shore. Where wave energy flows back out to sea. Daily change in sea-level due to gravitational pull of sun and moon. Gravitational pull of the sun and moon. Height and number of cycles per day vary around the globe. Semi diurnal, two high tides, two low tides, 24 hour period lower than other) Large tidal range = strong tidal currents. Tidal currents may dominate in an area and be the primary control on erosion and deposition. Timing of tidal cycle critical for determining the storm tide. Easily moved by wind, waves and tides. In winter, storm waves increase erosion; sand washed off beach is stored in bar offshore. In summer, smaller waves and tides re-deposit sand on beach.
