river exe

Question 1

key data facts of river exe

Answer 1

basin in 1300km2
56km long

long thin catchment
exmoor hills to exmouth

1300mm rain

65% runoff
1/3 enters soil

Question 2

overall + seasonal hydrograph

Answer 2

highest = feb 200m3/s
lowest = june 3 m3/s

lots fluctuation

highest winter 200 to 20
lowest summer 3 to 25

flashy

Question 3

relief factor

Answer 3

steep land
lots runoff
short lag
flashy

Upper:
Steep hills and moorland. Lots of rainfall which is channeled into river.

Middle:
Relatively steep topography

Lower course:
starts to flatten out

Question 4

draiange density factor

Answer 4

high density
feeds into river quick and picks up lots of water

Question 5

upper catchment characters

Answer 5

57% grassland - permeable soil
13% woodland - interception
24% arable land - crops take up water

1% peat bogs - were drained

5% urban - impermeable

Question 6

geology facts

Answer 6

61% low permeability

Devonian sandstone

• lots runoff , flood , flashy

Question 7

flood risk of river exe

Answer 7

11,000 properties at risk
1 in 100 yr prob flood

Tiverton exeter exmouth

Question 8

moorland drainage

Answer 8

18th cent - total moorland

18th/19th cent - ditches to drain for crops
lots flood

now - back to moorland as settlements bigger so more flood

Question 9

moorland restoration [exmoot mires project]

Answer 9

£2 mill spent
2000 Ha

block ditches

now 20% cheaper treat water as less sediment washed to river

• water in soil again so sphagnum moss grown - hold 20x weight
• hold 6000 olympic swimming pools
• 2.2cm rise water table
• flood peaks reduced
• 1/3 moisture retained

more carbon stored

Question 10

wimbleball reservoir

Answer 10

120 mill litres
regs discharge and supplies water

100% capacity past year with river still full and meet water needs [sustainable]

Question 11

urbanisation impact water cycle and river

Answer 11

impermeable surface
less infiltrate
surface runoff
flood [tiv, ex, exm]

drains
direct to river
burst banks
flood

Question 12

agriculture impact water cycle and river

Answer 12

67% land agricultural grassland
pastoral farm cows/sheep

cattle and machinery compact soil
less permeable
overland flow

les vegetated
less interception
overland flow

Question 13

role of peat bogs store carbo

Answer 13

carbon oxidises with oxygen in air when dry form co2

million tonnes could enter if ditches not repaired