river exe case study

Question 1

key facts

Answer 1

river exe flows 185.6 km through Exeter and Devon
network of tributaries running off it
high altitude 516m above sea level
source = exehead
mouth = exmouth
river discharge greatest in summer, lowest in winter = very flashy hydrograph

Question 2

physical impacts on flood hydrograph

Answer 2

land use
geology = 93.5% of ground is moderate/impermeable, increased runoff which reduces lag time
vegetation = 13% is coniferous woodland, majority used for agriculture, increased runoff
= flashy river regime exacerbates flood risk, 11,000 properties at risk from flooding (Exeter and Tiverton)

Question 3

anthropogenic impacts on flood hydrograph

Answer 3

urbanisation = increased housing to accommodate population growth reduces permeability of ground due to roads and infrastructure
agriculture = pastoral farming compacts soil which reduces percolation and infiltration, increases surface runoff which increases peak discharge, reduces lag time
- large areas of exmoor drained for grazing cattle to increase food supply after WWII, moorland no longer soaks up water

Question 4

mitigation: wimbleball reservoir

Answer 4

huge store of water, regulates water supply
120,000,000l of water held in reservoir
= reduces peak discharge, less flood risk

Question 5

mitigation: exmoor mires project

Answer 5

peatbog restoration:
- holds huge amounts of water (30x its weight in water)
- huge carbon store also, reduces carbon in atmosphere
encourages growth of sphagnum moss, soaks up huge amounts of water

Question 6

exmoor mires project success

Answer 6

exeter university monitors project
- 1/3 of water increased after restoration
- water table risen by 2.2cm