Exe Pt 2 Flashcards
(9 cards)
What is the impact of drainage ditches on the flood risk of the Exe?
Drainage ditched channel precipitation more quickly off the moorland and into rivers, reducing potential infiltration and increasing flood risk for properties in the lower catchment.
This is due to less water being stored on the moorland and more being transferred downstream via channel flow.
What human feature on the Exe makes the river less flashy than expected?
Wimbleball Reservoir regulates water flow, ensuring a steady regime throughout the year, preventing peaks and troughs that might cause flooding or drought.
Built in 1979, it is a significant water store.
What is being done to reverse damage done to the River Exe catchment?
Areas of peat moorland are being restored by the Exmoor Mires Partnership, and hundreds of kilometres of old ditches have been blocked to increase water storage on the moorlands.
This aims to create wetter, healthier peatland.
Evaluate the positive impact of the peatland restoration project on flood risk.
Water storage on the moorland has increased, with the water table rising by 2.65 cm and a 33% reduction in storm flow leaving restored sites.
Examination of the hydrograph shows a clear increase in base flow.
What limitations exist regarding the peatland restoration project?
The relatively small scale of the project limits its potential impact, although it could be extended in the future if landowners agree.
Future intense storms linked to climate change may counteract recent gains.
Describe the role of peatland in the local carbon cycle.
The moorland on Exmoor contains large amounts of peat, a major natural carbon sink made up of dead organic matter, including sphagnum moss.
Saturated conditions reduce decomposition, maintaining carbon storage.
How did the digging of drainage ditches change the carbon cycle?
Ditches caused the peat to dry out, making it more susceptible to erosion, leading to carbon in the peat dissolving in water and being transported downstream, affecting water quality.
This made the water brown and resulted in potential loss of carbon turning the peat from a sink to a source.
What is the effect of blocking ditches on the carbon cycle and water quality?
Blocking ditches results in wetter, healthier peatland, increasing carbon storage and improving water quality by reducing carbon dissolution in runoff.
Early results show a reduction of carbon leaving restored sites by up to 50%, though long-term data is needed.
Fill in the blank: The Wimbleball Reservoir was built in ______.
1979
