River Exe Case Study

Summary

This video explores the environmental and human factors shaping the River X's river regime. The river, with its steep terrain and impermeable geology, experiences rapid surface runoff, resulting in a flashy discharge. Human activities, including urbanization, farming, and water extraction, exacerbate flood risks in nearby areas. However, positive restoration efforts, like the Exmoor Myers Project, are reversing some of the damage by restoring peatland and increasing water retention, improving flood control and benefiting the carbon cycle. The video highlights both the challenges and solutions in managing this complex river system.

Takeaways

• 😀 The River X has a flashy river regime, with significant variations in discharge throughout the year, reaching peaks in winter months and falling sharply in summer.
• 😀 The catchment area of River X is located in the southwest of England, with steep slopes on Exmoor contributing to rapid surface runoff.
• 😀 The median altitude of the catchment area is 171 meters above sea level, with the highest point on Exmoor reaching 516 meters.
• 😀 The River X catchment has high drainage density, meaning there are numerous rivers and streams, which contributes to its flashy discharge regime.
• 😀 The land use in the River X catchment is dominated by agriculture (80.5%), including livestock grazing, which can contribute to rapid runoff due to soil compaction.
• 😀 The lack of woodland in the catchment (only 13%) leads to less interception of precipitation and increased surface runoff.
• 😀 The geology of the River X's catchment area is largely impermeable, with 93.5% of the bedrock being of moderate or low permeability, leading to reduced percolation and more runoff.
• 😀 The flashy river regime increases flood risk, with approximately 11,000 properties at risk in the catchment, especially in urban areas like Exeter.
• 😀 Human activities, including drainage of Exmoor's moorlands for farming, have increased runoff and contributed to a higher risk of flooding.
• 😀 The Exmoor Myers Project is a successful restoration initiative aimed at blocking drainage ditches on Exmoor to improve water retention, slow river flow, and reduce flood risk.
• 😀 Peatland restoration, such as the Exmoor Myers Project, not only helps manage water flow but also contributes positively to the carbon cycle by reducing CO2 emissions.

Q & A

What is the river regime of the River X?

The river regime of the River X is highly variable, with significant fluctuations in discharge throughout the year. It peaks in the winter months (November to March) and drops in the summer. The highest discharge is over 100 cubic meters per second, and the lowest point is around 4 cubic meters per second.

Why does the River X have such a flashy discharge regime?

The flashy discharge regime of River X is due to its steep topography, high altitude, and impermeable geology. Additionally, the large drainage density, with many tributaries, means that water flows quickly into the river, exacerbating the variability of discharge.

What are some of the key physical characteristics of the River X's catchment area?

The River X’s catchment is characterized by steep slopes, particularly in the upper course, with a median altitude of 171 meters. Exmoor, the source of the river, has an altitude of 516 meters. This contributes to increased rainfall and surface runoff.

How does the land use in the River X’s catchment area impact water runoff?

The land use, with 80.5% of the catchment being farmland (including 23.5% arable and 57% grassland), contributes to increased surface runoff. The lack of woodland, which typically intercepts precipitation and promotes infiltration, exacerbates runoff, leading to faster water flow into the river.

What is the impact of the River X's geology on its discharge?

The geology of the River X’s catchment is mostly made up of low to moderate permeability rocks (93.5%), which reduces water infiltration and percolation. This leads to quick saturation of soils and increased surface runoff, contributing to the flashy discharge regime.

What flood risks are posed by the flashy regime of the River X?

The flashy regime increases the risk of flooding, particularly in places like Exeter, Exmouth, and Tiverton. Around 11,000 properties are at risk of flooding, especially during high rainfall events, with the flood risk being most significant during heavy rain episodes.

What human activities have impacted the River X’s catchment area?

Human activities, particularly agriculture, water abstraction, and urbanization, have impacted the River X’s catchment. Draining of moorland for farming, compacting of soil by livestock, and the development of urban areas have all contributed to increased runoff and a heightened flood risk.

How did drainage ditches in Exmoor affect the water cycle?

Drainage ditches cut into Exmoor during the 1900s have altered the water cycle by reducing the ability of the moorland to retain water. Water now runs off quickly into these ditches, reaching the main river channel faster, contributing to the flashy discharge regime and increased flood risk.

What steps are being taken to restore the natural state of the River X’s catchment?

Efforts like the Exmoor Myers project focus on peatland restoration by blocking drainage ditches, slowing water flow, and increasing water retention in the catchment. These efforts aim to reduce flood risks, improve water quality, and enhance the carbon cycle by preserving peatlands.

What is the significance of the Exmoor Myers project?

The Exmoor Myers project, a collaboration between Southwest Water, the Environment Agency, and Exeter University, is restoring peatland areas by blocking drainage ditches. This helps slow water flow, improve water quality, and store more water in the catchment, reducing the risk of flooding downstream.