6 - coastal processes and deposition with associated landforms

Question 1

what are the processes of transportation

Answer 1

SOLUTION - dissolved in sea water, carried in solution, not visible
SUSPENSION - small particles carried in water
SALTATION - load bounced along sea bed, currents cant keep larger and heavier sediment afloat for long times
TRACTION - pebbles/larger sediment rolled along sea bed

Question 2

what is longshore drift

Answer 2

net movement of sediment along a coastline in zig zag form

waves move up beach in swash at direction of prevailing wind
waves drain back down beach as backwash at right angles to beach (gravity)

larger sediment needs more energy = slower pace of transport , smaller it is the faster it is

Question 3

how does the coast influence LSD

Answer 3

irregularities in shape of coastline = refraction not always achieved

= longshore drift, major force in transport of material

Question 4

what is gross and net littoral drift

Answer 4

GROSS littoral drift = total volume of sand transported both up and down coast

NET littoral drift = difference in upwardly and downwardly transported volumes of sand

Question 5

what is coastal deposition

Answer 5

DEPOSITION in open water occurs when energy of transporting water is too low to transport sediment

= laying down/depositing of material

Question 6

what is stokes law

Answer 6

stokes law defining sediment deposited by water = directly proportional to mass (size) of sediment being transported

larger material deposited first, smaller material transported further

Question 7

what is flocculation

Answer 7

clay particles aggregate together, forming larger material = floc

process increases mass of particles, deposition speeds up

flocculation beds deposited in deltas as rivers enter coastal waters and lose energy

Question 8

what is sediment storing

Answer 8

usually largest sediment deposited first, smaller further

however in shallow water, wave energy causes differential deposition and largest cobbles and boulders are thrown above high water mark by storm waves

Question 9

what are beaches

Answer 9

depositional landform
made of loose, unconsolidated sands/pebbles
they are mobile and able to adjust dynamic equilibrium

Question 10

how/when are beaches built up in UK

Answer 10

most beaches built up in summer months - long periods of stable, anticyclonic weather, constructive waves

lose mass in winter as depressions bring destructive waves

profiles change annually

Question 11

what are the three main types of beaches and what are they influenced by

Answer 11

main influence on beach profile = wave energy. prevailing wind conditions and sediment supply result in 3 main types:

• SWASH-ALIGNED
• DRIFT-ALIGNED
• ZETA-FORMED

Question 12

what is a swash aligned beach

Answer 12

• waves break parallel to shore
• little longshore drift
• sediment moving in onshore-offshore direction

Question 13

what is a drift aligned beach

Answer 13

• wave arrive at oblique angle
• lots of LSD
• plenty of sediment available
• depending on morphology, spits forming down drift end of beach

Question 14

what is a zeta formed beach

Answer 14

• form at oblique angle to dominant wave approach with LSD
• where headlands at each end cause wave refraction and block sediment movement
• at far end, sediment builds up in front of headland creating wider down drift

Question 15

what is a BERM and where/how is it formed

Answer 15

ridges of deposited material

• formed at top of foreshore of beach
• formed by deposition from top of swash during high tide

Question 16

what is a RIDGE/RUNNEL

Answer 16

raised bank of sand and trough forming runnel

• located on lower foreshore
• strong backwash on beach with low gradient = transported sand then deposited back to foreshore

Question 17

what is a RIPPLE

Answer 17

small ridges

• located in lower beach at back of foreshore
• caused by repeated orbital movement of water in waves

Question 18

how is a spit formed

Answer 18

1. beach material transported by LSD in direction of prevailing wind
2. change in direction of coastline transportation
3. deposition of larger, heavier storm material
4. further deposition making spit extend into estuary (spits can become narrow and breached if sediment supply interrupted)
5. change in direction of prevailing wind causing spit to curve (hook)as direction of transportation altered
6. silt deposited in sheltered area behind spit
7. salt marsh develops and becomes vegetated

Question 19

what is a bar

Answer 19

bars are elongated deposits of sand and shingle lying parallel to coast

laid down by constructive waves and separated from shore by lagoons varying in size

Question 20

how is an offshore bar formed (7 steps)

Answer 20

1. elongated ridges of sand/shingle parallel to coastline but unattached
2. waves approach gently sloping coast, friction between waves and sea bed = waves break and deposition occurs
3. more material builds up parallel to coast to form ridge of sand called offshore bar
4. body of coastal water could be completely shut off from open sea - lagoon
5. further deposition encouraged
6. submerged bars exposed at low tide and barrier islands partially exposed even at high tide
7. most material deposited onshore side of bar resulting in coastward migration

Question 21

what is a barrier beach/island

Answer 21

at macro scale, bars known as barrier beaches/islands. occuring in sea with shallow offshore gradients, low tidal range yet high wave energy

unlike small bars, they arent submerged at high tide

eg Fresian Islands

Question 22

what is a tombolo

Answer 22

TOMBOLO = complex features develop when LSD joins an island onto mainland or larger island. this island known as a tied island

some smaller tombolos formed when cuspate foreland linked up with islands

Question 23

what is a cuspate foreland

Answer 23

CUSPATE FORELAND = triangular shaped projections with apex pointing out to sea

varying in scale

Question 24

what causes a cuspate foreland to be formed

Answer 24

where sediment, moved by LSD, becomes trapped when equilibrium is reached between sediment inputs and there is energy available to move it

Question 25

how is a cuspate foreland formed

Answer 25

1. triangle shaped accretions of sand and shingle extend seaward
2. change in direction of coastland
3. LSD extending both directions due to two dominant wind directions
4. sediment brought in from both directions, foreland developed
5. possible joining of 2 spits, trapping sediment
6. sedimentation enhanced by rivers bringing sediment to their mouths

Question 26

how was dungeness formed (CP)

Answer 26

formed largely of shingle beach in form of cuspate foreland sheltering large area of low lying land called Romney Marsh

result of two directions of LSD

Question 27

describe beach equilibrium, what is involved and changes

Answer 27

a beach is a dynamic geomorphic system that is a buffer against erosion that can respond to changes:

when rate of sediment being added to beach equals amount leaving the beach resulting in the beach remaining the same size

if something happens the break this equilibrium (human actions, natural variations) the system will undertake negative feedback to restore equilibrium and sedimentary budget so erosion doesn’t increase