erosional landforms at the coast

discordant coastline

rock bands perpendicular to the sea are different

concordant coastline

rock bands parallel to the sea are the same

headland

more resistant rock and stick out into sea

bays

less resistant rock and eroded back by the sea

how headlands and bays form

hydraulic action and abrasion eroded less resistant rock faster than more resistant rock. differential erosion

Wave refraction

when wave reaches back of bay it has less energy so deposition occurs to form a beach. wave refraction causes waves energy to be concentrated on the headland, erosion will occur.

Caves arches stacks and stumps

crack is formed by hydraulic action. crack eroded by hydraulic action and abrasion forming a cave. continued erosion by hydraulic action and abrasion breaks through the back of the cave forming an arch. erosion and weathering at the top of the arch collapses forming a stack. erosion and weathering erodes stack forming a stump.

wave cut platform formation

crack between LT and HT eroded by hydraulic action. Top of cliff eroded by weathering. Crack eroded to a wave cut notch between LT and HT. Weathering causes top of cliff to collapse; cliff retreats.

Transportation of sediments

solution, suspension, traction, saltation

solution

dissolved chemicals in the water

suspension

particles carried in the water

traction

large pebbles rolled along seabed

saltation

bouncing motion of particles too heavy to be carried

Longshore drift

movement of sediment along beach by waves.

prevailing wind is wind direction & swash direction. swash moves up at an angle. backwash moves down at 90 angle

Formation of spits

longshore drift moves sediment to the end of the beach. sediment is deposited and grows the beach to form a spit. secondary wind changes direction of longshore drift and makes spit form a hook. salt marsh formed behind spit.

formation of bars

longshore drift occurs. deposits sediment at the end of beach and forms a spit. spit grows and joins beach on the other side forming a bar. lagoon left in old bay

formation of tombolos

longshore drift occurs at beach and deposition forms a spit. spit continues to grow until it reaches the island forming a tombolo

formation of sand dunes

needs a large flat beach, large supply of sand, onshore wind to move sand to the back of beach, and an obstacle.

hard engineering

structures built to alter the environment

soft engineering

adapt/encourage natural processes on the beach

sea wall - HE

built along cliffs/back of beach. curved so waves are reflected back on themselves & reduces its energy. expensive (5000 per metre). adv = seating, bicycle routes, security, lasts up to 50 yrs.

dis = destroys habitats, ugly, restricts access.

gabions - HE

boulders encased in wire mesh, absorb energy from waves. adv = blends in better, lasts 20 - 25 yrs.

dis = destroyed easily, damaged ones are ugly, people can get injured

groynes - HE

wooden barriers at right angles to stop longshore drift. adv = cheap, lasts up to 40 yrs, concrete crests for fishing/viewing.

dis = ugly, traps sediment & restricts supply of sediment downdrift, dangerous

rock armour - HE

boulders placed to absorb wave energy. adv = cheap, easy to build, lasts long time. dis = ugly, imported rocks doesn't match local geology, less access to beach

beach replacement - SE

shingle dredged from seabed and pumped onto beach. adv = wider beaches protect properties, attracts tourists, natural, more room. dis = cheaper but still expensive

sand dune regeneration - SE

sand dunes to absorb wave energy. adv = maintains habitat, cheap, protects land behind them. dis = deters tourists, fertilisers, not stable, expensive systems to prevent trampling, 2-3 years to become established

beach reprofiling

making wider beaches by using material already on the beach. adv = residents feel safe, protects ecosystems, natural. dis = steep, uninviting to tourists, expensive