case study: River Exe

Question 1

what are the characteristics of the river Exe’s basin in the upper course (near simonsbath)?

Answer 1

• land use - town, hotel, housing (concrete)
• little vegetation (few areas of forest)
• steep sloping land around the river - average 350m

Question 2

what are the characteristics of the middle course (near dulverton)?

Answer 2

• lots of vegetation (large areas of forest)
• rural - not many buildings - caravan park, farmland, castle
• not as steep as upper course, average approx. 250m

Question 3

what are the characteristics of the lower course (near Exeter)?

Answer 3

• high density buildings
• barely any vegetation (only golf course)
• low lying land - approx. 40m

Question 4

what are the characteristics of the wimbleball reservoir?

Answer 4

the dam impounds water from the river haddeo to form a reservoir with a net storage of 21,320 megalitres and surface area of 150 hectares

Question 5

what is the job of the wimbleball reservoir?

Answer 5

to supply Exeter and parts of east Devon by releasing water into the river exe. the water is then abstracted at Tiverton and Exeter. water also supplied by pipeline to Wessex waters Maundown water treatment works.o

Question 6

what happens as a result of the wimbleball reservoir?

Answer 6

peak discharge lowered, regulates and controls discharge throughout the year, helps meet demand and decreases likelihood of flooding

Question 7

what caused the problem on the Exmoor mires?

Answer 7

drainage ditches dug and peat cutting. this causes the mires to dry out, which reduces the water capacity of the moors.

Question 8

what happens as a result of the drying of the moors?

Answer 8

oxidation of exposed peat bogs, releasing large quantities of carbon into the atmosphere

Question 9

what has been done as a result of the Exmoor mires project?

Answer 9

blocking drainage ditches using sustainable methods, local materials, contractors in order to rewet the bog, enabling it to retain water and carbon.

Question 10

what impact has the work done by the project had?

Answer 10

• re-wetted peat bogs slow down the run-off of water from land before steadily releasing it
• floods less likely, reduced soil erosion and the amount of silt entering the rivers
• peat cuttings reduce surges after storm event, minimising flood damage - 1/3 less water in storms
• water naturally filtered through the vegetated peat
• slower flow of water gives suspended particles in water more time to settle = reduction of suspended particles and dissolved organic carbon (DOC) - 30% less

Question 11

what is a benefit of reduced amount of silt entering rivers?

Answer 11

water is 20% less expensive to treat

Question 12

what areas are at the most risk from flooding?

Answer 12

Exeter and Exmouth - 2,000 to 5,000 properties at risk

Question 13

what areas are at the least risk from flooding?

Answer 13

Cowley and Bampton - 100 to 250 properties at risk