Hard Engineering Defences – Built Structures

  • Sea wall- reflects waves back out to sea, preventing erosion and flooding, expensive creates a strong backwash which erodes under the wall.
  • Revetment- slanted structures built at the foot of cliffs; waves break against them which reduces their power, expensive to build and create a strong backwash.
  • Gabions- rock-filled cages which absorb wave energy, cheap and ugly.
  • Riprap- boulders piled up along the coast and they absorb wave energy, cheap and change shift in storms.
  • Groynes- fences built at right angles to the coast which trap material transported by longshore drift, cheap and starve beaches further along.
  • Breakwaters- concrete block or boulders deposited off the coast which force waves to break offshore; reducing wave power is expensive and can be damaged in storms.
  • Earth bank- mounds of Earth act as a barrier to prevent flooding which are expensive and can be eroded.
  • Tidal barrier- built across river estuaries; contain flood gates which are expensive.
  • Tidal barrage- dams built across river estuaries; hold water at high tide and control release of it which is expensive and disrupt sediment flow which increases erosion elsewhere.