Coastal Geography, Wave Induced Currents

Question 1

What are the three types of wave induced currents?

Answer 1

Refraction, difraction, and reflection

Question 2

Wave refraction

Answer 2

Waves bending at different water depths.

Full refraction = Aligned to shoreline

Question 3

Wave diffraction

Answer 3

Wave crests are fragmented and redirected due to obstacles which subsequently form a wave shadow zone. These fragments may remcombine later on.

Question 4

Wave shadow zone

Answer 4

The quiet water behind an obstacle that has diffracted waves

Question 5

Wave reflection

Answer 5

Waves bouncing off the shoreline. This is common on steep beaches

Question 6

Rip currents

Answer 6

A strong seaward current that is responsible for taking excess water and sediment offshore

Question 7

How do rip currents form?

Answer 7

From edge wave eroding the seafloor which causes waves to not break because of the increased water depth

Question 8

What are the six components of nearshore cell circulation?

Answer 8

Mass transport, breaker zone, longshore feeder currents, rip currents, rip head, and bed return flow

Question 9

Mass transport

Answer 9

Slow, onshore movement of water

Question 10

Breaker zone

Answer 10

Area of breaking waves

Question 11

Longshore feeder current

Answer 11

Carry water into rip

Question 12

Rip current

Answer 12

Seaward return flow of water

Question 13

Rip head

Answer 13

Seaward end of rip current beyond the breaker zone

Question 14

Bed return flow/undertow

Answer 14

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

Question 15

Longshore currents

Answer 15

Refers to waves that haven’t fully refracted to align with the shore, thus reaching the coast at an non-parallel angle.

Question 16

How are fully refracted longshore currents different from partially refracted longshore currents?

Answer 16

Partially refracted longshore currents have greater velcoity due to the increased angle of approach.

Question 17

How do wave induced currents affect sand movement?

Answer 17

The orbital motion of water kicks up sediment when reaching shallow waters, allowing it to be transported both onshore and offshore

Question 18

What two types of waves/currents carry water onshore?

Answer 18

Waves and swash

Question 19

What three types of waves/currents carry water offshore?

Answer 19

Backwash, rip currents, and bed return flow

Question 20

What two types of waves/currents carry water alongshore?

Answer 20

Longshore currents and longshore feeder currents

Question 21

Longshore drift

Answer 21

The general movement of sediment along the shoreline due to the interaction of swash and backwash

Question 22

Why are longshore currents, longshore drift, and nearshore cell circulation significant?

Answer 22

These three processes change the morphology of the coastline

Question 23

Headland bypassing

Answer 23

The movement of sediment around rocky headlands by waves and tides.

Question 24

What happens to sand/sediment around headlands?

Answer 24

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