Topic3(5)- Coastal Management Flashcards
Aims of coastal management
1)protect homes,businesses, and environment from erosion
3 main categories of impacts erosion can cause
Social
Economic
Environmental
Why isnt everywhere defended and how do people choose where to protect
- money available (limited) especially in LIC’s
- Cost benefit analysis (large settlements/important industrial sites rather than isolated small settlements)
4 main options for coastal management
1) hold the line
2) advance the line
3) do nothing
4) managed retreat
Types of hard engineering
1) Sea walls
2) Revetments
3) gabions
4) riprap
5) groynes
6) breakwaters
7) earthbank
8) tidal barrier
9) tidal barrage
Sea walls
-how do they work
Reflects water back out to sea, preventing erosion
Cost(price) of sea wall and disadvantages
- Expensive to build and maintain
- Creates a strong backwash which erodes under the wall.
Revetments
-how do they work
- Slanted structures built at cliff foot
- made from concrete/wood/rocks
- absorb wave energy and so prevent cliff erosion
Revetments
-disadvantages/cost (price)
-Create a strong backwash, but relatively cheap
Gabions-
How do they work
- rock filled cages
- built at foot of cliffs
- absorb wave energy and so reduce wave erosion
Gabions-
Price/disadvantages
- cheap
- ugly
Ripraps
-how do they work
-boulders piled up along coast absorb wave energy, so reduce erosion
Ripraps
-cost/disadvantages
-fairly cheap/ can shift in storms
Groynes-
How do they work
- fences built at right angles to coast
- trap beach material transported by longshore drift
- creates wider beaches, which slow the waves- reducing energy so less erosion
Groynes
-cost/disadvantages
-quite cheap/ starve beaches further down of sediment; so they have thinner beaches, therefore less protection from erosion/flooding
Breakwaters
-how do they work
- concrete blocks/boulders deposited off the coast
- force waves to break offshore
- waves energy reduced before they reach shore
Breakwaters
-cost/disadvantages
- expensive
- can be damaged in storms
Earth bank
-how does it work
Mounds of earth act as barrier to flooding
Earth banks
-cost/disadvantages
- quite expensive
- can be eroded
Tidal barrier-
How does it work
- built across river estuaries
- contain retractable floodgates that can be raised to prevent flooding from storm surges
Tidal barrier-
-cost/ disadvantages
-VERY expensive
Tidal barrage
-how does it work
- dams built across river estuaries
- generate electricity
- water trapped behind dam at high tide
- controlled water release( turbines)
- prevent flooding from storm surges
Tidal barrage
-cost/disadvantages
- VERY expensive
- disrupt sediment flow-may cause increased erosion elsewhere
