OCR Nationals Spec. B - Coasts

• Hydraulic Action - Force of waves which cause the cliffs to crack, break apart and corrode.

• Abrasion - Powerful waves pick up stones and throw them against the base of a cliff which attacks the cliff over time.

• Attrition - Stones smash into each other and break apart as the sea carries them. They slowly get smaller and rounder.

• Corrosion/Solution - Chemicals in a sea dissolve rocks such as chalk and limestone.
• 

• High and steep
• Backwash> swash (Materials removed from the coast)
• Factors that affect the size and power:
  • Wind - Strong Wind = large powerful waves
  • Fetch - Strong Fetch = bigger and more powerful waves.

• Deposit more material than they erode
• Low and long
• Swash > backwash
  • swash carries material to a coast
  • Backwash doesn't take a lot of material back down to coast = deposited
• Weaker winds and shorter fetch than destructive waves.

• Waves attack the base of the cliff
• Cliff under cot and wave cut notch forms, this enlarges as erosion continues, cliff above notch becomes unstable and collapses.
• Collapsed material is washed away and a new wave cut notch forms.
• Repeated collapsing results in cliff retreating.
• Wave cut platform is the platform left behind as the cliff retreats.

• soft rock = quick retreat

• More Vegetation = more stable = less erosion = slow retreat

·         Resistant rocks with cracks – enlarged by waves crashing

·         Repeated erosion and enlargement of cracks cause a CAVE to form

·         Erosion breaks through the headland forming an ARCH

·         Rock supporting arch wears way forming a STACK

·         Stack worn away to give a STUMP which can be covered by high tides

·         Material is transported along coasts

·     Waves follow the direction of the prevailing wind

·    Hit coast as an oblique angle

·    Swash carries material up the beach in the same direction as the wind

·    Backwash carries material down the beach at right angle, back towards the sea

·         Beaches that stick out in the sea. They’re joined to the coast at on end

·         Form at sharp bends in the coastline

·         LSD transports sand past the bend and deposits it in the sea

·         Behind the spit it is a sheltered area which is protected from waves

·         The sheltered area accumulates a lot of material and over time becomes salt marsh

·         Spit connects with another bit of mainland

·         Bar cuts off the bay between the headland and the sea

·         Logoon can form behind the bar

·         Bar that connects the shore to an island is called a tombolo

·         Loss of tourism

·         Businesses near cliff – collapse – damage – money – shut down

·         Agricultural land – damage – poor soil fertility

·         Property prices – decrease – can’t insure it

·         Death

·         Water supplies polluted

·         Loss of homes (homeless)

·         Loss of jobs

·         Damage of roads

· High salt content = kill organisms

·  Force of flood water = uproots trees and plants

Sea Wall

• reflects waves
• Prevents erosion, barrier to flooding
• Expensive, strong backwash = erosion.

Rip Rap

• Boulders
• absorb wave energy
• Moved around by strong waves

Groynes

• Right angle, trap materials from LSD
• wider beaches = slower waves
• Starve beach as narrow, which means poor protection = erosion

Rip Rap Armour -

• Foot of Cliff
• Absorb wave energy
• Expensive. Strong BW = erosion

Gabions

• rock filled cages
• Absorb wave energy
• Not Attractive

Beach Nourishment

• Sand added to the beach
• wider beaches = slower waves
• Expensive and needs reacting