Coastal Geography, Wave Induced Currents Flashcards
What are the three types of wave induced currents?
Refraction, difraction, and reflection
Wave refraction
Waves bending at different water depths.
Full refraction = Aligned to shoreline
Wave diffraction
Wave crests are fragmented and redirected due to obstacles which subsequently form a wave shadow zone. These fragments may remcombine later on.
Wave shadow zone
The quiet water behind an obstacle that has diffracted waves
Wave reflection
Waves bouncing off the shoreline. This is common on steep beaches
Rip currents
A strong seaward current that is responsible for taking excess water and sediment offshore
How do rip currents form?
From edge wave eroding the seafloor which causes waves to not break because of the increased water depth
What are the six components of nearshore cell circulation?
Mass transport, breaker zone, longshore feeder currents, rip currents, rip head, and bed return flow
Mass transport
Slow, onshore movement of water
Breaker zone
Area of breaking waves
Longshore feeder current
Carry water into rip
Rip current
Seaward return flow of water
Rip head
Seaward end of rip current beyond the breaker zone
Bed return flow/undertow
The seward flow of water on the seafloor that exists benath the onshore flow. It is responsible for picking up sediment and eroding the seafloor
Longshore currents
Refers to waves that haven’t fully refracted to align with the shore, thus reaching the coast at an non-parallel angle.
How are fully refracted longshore currents different from partially refracted longshore currents?
Partially refracted longshore currents have greater velcoity due to the increased angle of approach.
How do wave induced currents affect sand movement?
The orbital motion of water kicks up sediment when reaching shallow waters, allowing it to be transported both onshore and offshore
What two types of waves/currents carry water onshore?
Waves and swash
What three types of waves/currents carry water offshore?
Backwash, rip currents, and bed return flow
What two types of waves/currents carry water alongshore?
Longshore currents and longshore feeder currents
Longshore drift
The general movement of sediment along the shoreline due to the interaction of swash and backwash
Why are longshore currents, longshore drift, and nearshore cell circulation significant?
These three processes change the morphology of the coastline
Headland bypassing
The movement of sediment around rocky headlands by waves and tides.
What happens to sand/sediment around headlands?
The combination of longshore transport and the obstruction causes sediment to accumulate around the headland. Too much accumualtion causes the sediment to be carried around the headland, thus bypassing it
