3.1.3.4 Coastal Management Flashcards
what is the aim of coastal management?
to protect homes, business and the environment from the risk of erosion and flooding
how are places chosen to be protected?
cost-benefit analysis
what are the four options for coastal management?
Hold the line
Advance the Line
Do nothing
Manage retreat
what are different hard engineering strategies
sea wall revetments gabions rip rap groynes tidal barrier
how do sea walls operate?
reflect wave energy back to sea, preventing erosion of the coast
acts as a flood barrier too
how do revetments operate?
slanted structures at the foot of cliffs to stop cliff erosion as they absorb and break wave energy
what are gabions and what do they do?
cages of rocks that absorb wave energy to reduce erosion
what is rip rap and what does it do?
boulders piled against the coastline to absorb wave energy and reduce the rates of erosion
what are groynes and what do they do
fences built at right angles to the coast
they trap material transported by longshore drift
which creates wider beaches which slow waves
what are tidal barriers and what do they do?
built across river estuaries
contain retractable flood gates that can be prevented to prevent flooding from storm surges
cost / disadvantage of sea walls
£6000/m
creates strong back wash which erodes under the wall
needs consistent maintenance
ugly
cost / disadvantage of revetments
£4500/m
less durable than sea wall
cost / disadvantage of gabions
cheap but ugly
cost / disadvantage of rip rap
£1000/m
still lets water through so some erosion still takes place
easily moved by high energy waves
cost / disadvantage of groynes
£1000/m
cause erosion to increase further down the coastline
last up to 40 years
cost / disadvantage of tidal barriers
VERY expensive
Thames barrier total construction cost was £534 million which is equivalent to £1.6 billion at 2016 prices