The River Catchment Case Study: River Holford Flashcards
Where is the River Holford located?
The River Holford is in the Quantock Hills, Somerset, England. It is 4.5 miles long and flows into the Bristol Channel at Kilve Beach.
What is the geology of the River Holford catchment?
The river sits on sandstone geology, which is impermeable, preventing percolation into the rock layer.
How does vegetation influence water movement in the River Holford catchment? (2 things)
• Upper slopes: Maritime heather moorland, intercepting rainfall.
• Lower slopes: Forested, allowing infiltration into peat soils.
How does rainfall occur in the River Holford catchment? (3 things)
• Prevailing winds from the southwest bring moisture from the Atlantic.
• Relief rainfall occurs as air rises over the Quantock Hills.
• Average annual rainfall: 790-890mm.
How does water enter the River Holford?
Water flows from saturated soils at the source into a narrow, shallow channel.
What were the results of the infiltration fieldwork study? (2 things)
• Near the river channel: Infiltration rate was higher (2.15cm/min), suggesting most water reached the river through throughflow.
• Further up the valley: Infiltration rate was lower (0.1cm/min), suggesting more surface runoff.
How does geology affect infiltration in the River Holford catchment? (2 things)
• Upper areas: Impermeable sandstone, leading to more runoff and less infiltration.
• Lower areas: Permeable limestone, allowing greater infiltration.
Why is flooding unlikely in the upper course of the River Holford? (2 things)
• Water enters the river slowly through throughflow and soil water storage.
• Steep slopes prevent long-term accumulation.
Why is Holford village in the middle course prone to flooding? (2 things and example)
• Gentler gradient slows water movement.
• More impermeable surfaces (roads, houses).
- Example: Flooding in February 2014 due to Storm Amber (heavy rain, 80mph winds).
How is flooding managed in the lower course at Kilve? (3 things)
• The river flows through flat land and is carefully managed.
• Kilve village has flood defences to prevent flooding.
• The river forms a pool on the beach before reaching the sea.
