River Exe Flashcards
(21 cards)
Where is the River Exe located and how long is it?
It is in southwest England, 82.7 km long, flowing from the Exmoor Hills to the sea at Exmouth.
What is the source of the River Exe?
The Exmoor Hills at 514 metres elevation.
What is the size and nature of the upper catchment?
60 km² with steep topography.
What type of rock underlies most of the River Exe basin?
84.4% is impermeable rock, causing fast runoff and throughflow.
What are the main land uses in the River Exe catchment?
67% agricultural grassland, 15% woodland, 3% moors and peat bogs, <5% urban.
What is the annual rainfall in the River Exe catchment?
~1,200 mm/year (up to 2,300 mm in upland Exmoor).
What percentage of rainfall becomes runoff?
65% becomes runoff.
What is the River Exe’s discharge like throughout the year?
Highly variable—4 m³/s in summer and up to 120 m³/s in winter.
What causes the River Exe’s flashy regime?
Steep slopes, impermeable bedrock, low woodland cover, high drainage density, and quick soil saturation.
How does the degradation of peat bogs affect the river system?
Increases runoff and sediment transport, reducing natural water storage.
How did moorland drainage in the 19th–20th centuries impact the River Exe?
Reduced water storage and increased flood risk due to higher surface runoff.
What impact does urbanisation have on the River Exe catchment?
Increases impermeable surfaces and water demand, raising flood risk.
What are the effects of agriculture in the River Exe basin?
Soil compaction and erosion increase surface runoff and river sedimentation.
What role does Wimbleball Reservoir play?
Stores 120 million litres of water, regulates river flow, reduces floods, and supplies water.
How many properties are at flood risk in the River Exe catchment?
About 11,000, especially in Exeter and Tiverton.
What causes high flood risk in the River Exe basin?
Flashy regime, steep slopes, impermeable geology, and intense rainfall.
What is the aim of the Exmoor Mires Project?
Restore peat bogs to increase water storage and reduce flood risk.
How does the Exmoor Mires Project work?
Blocking drainage ditches with peat dams and barriers, promoting sphagnum moss growth.
What are the effects of the Exmoor Mires Project?
Increased water storage (33%)
Raised water table (2.2 cm)
Reduced flood and drought risk
Less sediment and CO₂ emissions
Retained water equal to 6,000 Olympic pools
What sustainable land use strategies are used in the River Exe basin?
Better grazing/soil management and tree planting to increase interception.
What flood defences are used in urban areas like Exeter?
Flood walls, barriers, and Sustainable Drainage Systems (SuDS).
