river defences

Question 1

Dams (HE)

Answer 1

a wall built across a river, usually in the upper course, with a resevoir stored behind it. Resevoirs can store water for drinking and HEP and reduces the risk of flooding

Disadvantages - very expensive, resevoirs flood large areas of land

Question 2

Channel straightening (HE)

Answer 2

the river;s course is straightened and meanders are cut out. water moves more quickly which reduces the risk of flooding.

disadvantages - flooding may occur downstream, more erosion as water is faster

Question 3

Embankments (HE)

Answer 3

raised walls built along the river bed. increased channel size meaning that the river can hold more water, reducing the risk of floodings.

disadvantages - expensive, risk of more severe flooding if they break or if water goes over the top

Question 4

Afforestation (SE)

Answer 4

a woodland is created in order to increase interception and transpiration. Discharge and flood risk are reduced; vegetation reduces soil erosion and builds habitats.

disadvantages - trees take time to become mature and grow

Question 5

river restoration (SE)

Answer 5

the river is made more natural and returned to its original course. e.g embankments are removed to allow the river to flood the floodplain naturally. reduces risk of flooding downstream as discharge is reduced.

disadvantage - local flood risk increases

Question 6

floodplain zoning (SE)

Answer 6

different uses of land are restricted to different locations along a floodplain. Areas closest to the river are used for low-value land use. Flooding reduced as impermeable surfaces are away from river, reduces impacts.

disadvantages - cannot be used where land has already been built on.