Coastal Processes

Question 1

Wave Refraction

Answer 1

1) Waves bending with land as approach shore
2) Caused when waves are not parallel to shore OR if coastline uneven
3) Portion of wave reaching shallow water first slows down + causes wave line to bend (refract)

Question 2

Effect of wave refraction

Answer 2

1) Smooths out coastline by wearing back headlands + increasing sediment accumulation

Question 2

Headland

Answer 2

1) part that juts out in coast –> more erosion since waves have more energy
2) salt wedging + pneumatic weathering

Question 3

Wave Erosion

Answer 3

1) Continually pounds shore
2) Storms bring huge strong waves, moving ~70 mph
3) Loosens rocks in coastline by forcing air into them, creating pneumatic action
4) saltwater = saltwater wedging in onshore rocks/cliffs

Question 4

Tsunami

Answer 4

major oceanic wave system caused by sudden disruption

Question 5

How are tsunamis formed

Answer 5

1) Abrupt movement on ocean floor, especially from reverse/thrust faults
2) Faults –> cause entire column of water to be disrupted –> shifts enormous volume of water
3) tsunamis in open water are small BUT have long wavelengths (125 miles) BUT this changes when it approaches coast + slows down

Question 6

Tsunami effects

Answer 6

1) Arrive as very rapidly advancing surge of water up to 130 feet high
2) immediately behind wave crest is enormous volume of water that goes deep inland

Question 7

Longshore Currents

Answer 7

1) causes water + sediment moves parallel to shoreline
2) caused by waves striking coast at slight angle
3) longshore currents = reflect local wind direction

Question 8

Beach drifting

Answer 8

1) zigzag movement - short distance shifting of sand
2) sand is moved forward by waves BUT some is brought back when wave recedes + cycle keeps repeating

Question 9

Beach

Answer 9

1) exposed deposit of loose sediment adjacent to water
2) relatively homogenous sediment

Question 10

Beach profile

Answer 10

1) Backshore = upper part of beach + usually dry except when severe storms
2) foreshore = regularly covered + uncovered by tides
3) nearshore = place where waves break + surf action greatest; never exposed to atmosphere
4) offshore = always underwater AND deep enough that wave action doesn’t influence bottom

Question 11

Sediment budget

Answer 11

Amount of sediment deposited by waves = amount of sediment removed
can change significantly during storms

Question 12

Spits

Answer 12

1) Linear deposit of sediment attached to land at one end + extending into open water (in direction of longshore current)
2) can go connect land on other side OR move inward toward mainland

Question 13

Baymouth Bar

Answer 13

1) spit that connects two separate pieces of land
2) “trapped” water is called a lagoon

Question 14

Tombolo

Answer 14

1) Spit that connects mainland to a tiny island close by
2) acts like bridge of sorts

Question 15

Barrier Island

Answer 15

1) Long, narrow island built up in shallow offshore waters
2) created by deposition of sediment when large waves “break” in shallow waters of continental shelves (reduced CC bc of slowed velocity)

Question 16

Barrier Island Lagoon

Answer 16

1) Forms when barrier islands isolate water between itself + mainland
2) Results in more deposition of sediment from coastal streams + tidal deposits + wind –> creates mudflats –> coastal marshes

Question 17

Barrier Island “migration”

Answer 17

1) After barrier island reaches certain size –> migrates shoreward bc more sediment deposited
2) Eventually merges with mainland

Question 18

Problem with barrier islands

Answer 18

1) Very susceptible to large storms BC it’s just few meters above sea level

Question 19

Groin

Answer 19

1) short wall/dam designed to impede longshore current + force sand deposition on up-current side of structure (reduced CC)
2) problem = does not stop erosion on the back side (down-current side) SO you could build a series of groins (groin field)
3) side where sand piles up IS where the longshore current comes from

Question 20

Jetties

Answer 20

1) Built in pairs on either side of river
2) Confines flow of water to narrow zone + inhibits deposition in navigation channel
3) goal = maintain clear navigation channel by controlling sediment deposition
4) Whichever one has more sediment, that’s where longshore current comes from

Question 21

Breakwaters

Answer 21

1) designed to provide shelter to small craft at anchor
2) horizontal bar behind which small boats can dock –> area inside breakwater has reduced energy + CC –> deposition
3) Must have angular face presented to wave approach + creates tombolos

Question 22

Sea Wall

Answer 22

1) Massive structure originally designed to prevent storm-induced flooding BUT now used as beach-protection structure
2) High enough to block storm surge + parallel to shoreline –> traps sediment in trapped water bc of reduced CC
3) BEHIND the beach

Question 23

Anatomy of a Wave

Answer 23

1) Crest = top
2) Trough = bottom
3) crest - crest = wavelength
4) wave height = amplitude

Question 24

Why do waves increase in height as they approach shore

Answer 24

1) as approach beach, water is not as deep SO there is more friction –> energy needs to go somewhere, increasing height

Question 25

Swash vs backwash

Answer 25

1) swash - wave hits + goes upward on coast
2) backwash - wave going backwards
SMOOTHING + SHAPING COAST