Coasts

• The 4 types of erosion

  1. hydraulic action
  2. Abrasion
  3. Attrition
  4. Solution
• Properties of destructive waves

  1. Have a high frequency (10-14 waves per min)
  2. Are high and steep
  3. Stronger backwash than swash
  4. carries out erosion
• Properties of constructive wavers

  1. Have a low frequency (6-8 waves per min)
  2. Are low and long
  3. Swash is more powerful than backwash
  4. carries out deposition
• Longshore Drift

  1. Waves follow the prevailing wind direction
  2. hit the coast at am oblique angle
  3. Swash carries material up the beach
  4. backwash carries material down the beach at a right angle (makes the zig-zag movement)
• 4 types of transportation

  1. Traction
  2. Suspension
  3. Saltation
  4. Solution
• Deposition

  When material is deposited or left behind
• Two types of coastlines

  1. Concordant (alternating bands of hard and soft rock parallel to the coast)
  2. Discordant (alternating bands of hard and soft rock at a right angle to the coast)
• How climate affects the coasts

  1. different temperatures can have an impact on salt or freeze thaw weathering
  2. More storms mean more destructive waves and saturated cliffs
  3. Prevailing winds (Direction if LSD)
• Wave cut platform

  1. waves cause erosion at foot of the cliff
  2. this forms a wave cut notch
  3. over time the notch becomes unstable due to more erosion
  4. the material collapse and is washed away and new notch forms
  5. repeated process cause cliff to retreat
  6. a wave cut platform is left as the cliff retreats
• Headlands and bays (formed along Discordant coasts)

  1. The rock with low resistance to erosion erodes quickly
  2. this forms a bay with a gentle slope
  3. The more resistant rock is eroded more slowly and sticks out forming a headland
• Headlands ----> Stacks

  1. Waves crash into headlands and erode by Hydraulic action and abrasion
  2. Repeated erosion causes a cave to form
  3. continued erosion causes the cave to deepen until it breaks through and forms a arch
  4. Erosion wears away at the supporting rock until the arch collapse
  5. A stack is now formed sepreate from the headland
• Beaches

  1. Sand beaches are flat and wide. Due to weak backwash it forms a gentle slope
  2. Shingle beaches are steep and narrow. Since weak backwash can't move the shingle it forms a steep slope
• Spits

  1. Longshore drift transports sediment until the coast changes direction and deposits material due to low energy
  2. Strong winds and waves curve the end of the spit
  3. The area behind the spit becomes a salt marsh or mud flat due to it being protected from waves
• Bars

  1. When a spit crosses over a bay
  2. the bar cuts off the bay between the headlands
  3. A lagoon is formed behind the bar
• How do humans affect the coast (Industry)

  1. Coastal quarries (exposes rock)
  2. Gravel extraction (Less protection for cliffs)
  3. Ports (Building on salt marshes)
• How do Humans affect the coast (Urbanisation)

  1. Coast have more infrastructure
  2. Increase in coastal defenses
  3. Restricted sediment supply to beaches
• How humans affect the coast (Agriculture)

  1. Clearing vegetation can expose soil (clifftops are vulnerable)
  2. Marshland is drained
  3. Agriculture land is left unprotected
• Impacts of coastal flooding on people

  1. Coastal industries may shutdown
  2. Cut off of tourism
  3. damage to infrastructure such as train lines
  4. Housing lost to sea
• Impacts of coastal flooding on the Environment

  1. Force of floodwater can uproot trees
  2. brings saltwater into freshwater ecosystems
  3. conservation areas are at risk
• What is hard Engineering

  Man-made structures built to reduce flooding and erosion
• What is Soft Engineering

  Schemes set up using knowledge of natural process to reduce the affects flooding and erosion
• Sea wall

  • A wall made up of hard material like concrete that reflects the waves back into the sea

  + Prevents coastal erosion

  + Acts as a barrier against flooding

  = strong backwash is created which erodes under the wall

  = Are very expensive
• Rip rap

  • Boulders piled up against the coast
  • act as a sea wall as the gaps absorb wave energy

  + reduces erosion and flooding

  + is fairly cheap

  = need to be replace as they move around

  = no new material replenishing the beaches as cliff isn't eroding
• Groynes

  • Wooden or stone fences that are built at right angles
  • trap material to stop LSD and build up the beach

  + They create wider beaches which slows waves which reduces erosion and flooding

  + fairly cheap

  = Starve beaches further down the coast

  = Beaches further down the coast have greater erosion and flooding
• beach nourishment

  • Sand or shingle from elsewhere are added to the upper part of beaches

  + creates wider beaches

  + protection from erosion and flooding

  = taking material from the seabed can kill sea creatures

  = expensive

  = has to be repeated