River Exe Flashcards
1
Q
Where is the river Exe?
A
- flows for 83km from its source in Exmoor, through Exeter and to the sea at Exmouth on the south coast of Devon
2
Q
What is land-use like?
A
- most of the land is agricultural grassland (67%) with 15% woodland. On the high ground of Exmoor, there are moors and peat bogs
3
Q
What is geology like?
A
84.4% is underlain by impermeable rocks so overland flow is high and infiltration is low
4
Q
How have recent developments affected the water cycle?
A
- construction of Wimbledon reservoir - regulates water flow and prevents the peaks and troughs of water discharge that lead to droughts and flooding
- peatland restoration on Exmoor - for decades, ditches have been dug in peat bogs to make it suitable for farming which has increased the speed of water flow and reduces water quality as more silt is carried downstream. The Exmoor mires project aims to block the drainage ditches which increases water content and helps to retain carbon stores within peat
this will lead to:
- increased water storage in upper catchments
- improved water quality
- more carbon storage
5
Q
Facts about the Exmoor mires project
A
- aims to restore 2000ha by blocking drainage ditches with peat bogs
- by 2015, over 1000ha restored and 100km drainage ditches blocked, raising the water table by 2.65cm
6
Q
How has flooding affected the river Exe?
A
- October 1960, half of the average annual rainfall fell (380mm), leading to devastating flooding
- hard engineering strategies were employed to prevent further flooding at a cost of £8 million
7
Q
What hard engineering strategies have been implemented?
A
- 3 flood relief channels eg. in Cowley
- radial gates which divert excess water into the Exwick relief channels
- levees and embankments to increase capacity
8
Q
What other flood defence strategies have been implemented?
A
- peat bog restoration leading to the equivalent of 104 olympic pools of water extra being held
- deepening trews flood relief channel and removing a weir
- scheme cost £30 million
9
Q
Why does peat need to be wet?
A
dry peat released CO2 through oxidation, wet peat absorbs and stores CO2
