Drainage basins of the UK Flashcards
What 5 factors influence the rate of which water moves through a drainage basin?
Type + quantity of rainfall Type + quantity of vegetation cover Size + shape of drainage basin Steepness of slopes Geology + soil type within the drainage basin
Define drainage basin
The area of land drained by a river.
Define interception
When rainfall does not reach the ground as it is blocked by trees, buildings etc.
Define infiltration
The movement of water into the soil.
Define throughflow
The downhill flow of water through soil.
Define overland flow
The flow of water over the surface of the land.
Define groundwater flow
The flow of water through rocks.
Define transpiration.
Water given off by plants.
Define stem flow.
Movement of water that has been intercepted down the stem or trunk of a plant.
Define percolation
Movement of water from the soil into the bedrock.
List the flows in a drainage basin.
Infiltration Percolation Overland flow Through flow Groundwater flow Evaporation Precipitation Transpiration Stem flow
List the stores in a drainage basin.
Atmosphere Vegetation Ground surface Soil Rocks Rivers and lakes Oceans
What physical and human factors cause rivers to flood?
Climate (physical)
Geology (physical)
Urbanisation (human)
Vegetation (physical)
How does seasonal rainfall cause rivers to flood?
Continuous rainfall causes ground to become saturated, leading to more overland flow - therefore higher river levels.
How does a storm event cause rivers to flood?
Brings high volume of rainfall in short period of time, causes sudden rise in river levels that can lead to flash floods.
How does heavy rainfall cause rivers to flood?
Lower chance of heavy rainfall being infiltrated, so runs off into river. The faster the water reaches river, more likely it is for it to flood.
How does prolonged rainfall cause rivers to flood?
If rains a lot, land around river can become saturated. If more rainfall, can’t be infiltrated, so runs along the surface - surface runoff.
How does geology cause rivers to flood?
Impermeable rocks don’t allow water to pass through them, so little water passes through, more overland flow so higher flood risk.
If valley made up of impermeable rocks, higher chance of flooding as increase in surface runoff.
How does steep relief cause rivers to flood?
Steeper valleys are more likely to flood than a flatter valley as the rainfall will run-off into the river quicker.
How does vegetation/deforestation cause rivers to flood?
Trees + plants absorb water (interception), so reduces flood risks. Deforestation increases risks of floods, as water isn’t intercepted, so quicker saturation + water will flow into the river quickly.
How does urbanisation cause rivers to flood?
Area surrounding river is built on, ground is covered with impermeable surfaces (tarmac and concrete) - reduces amount of water infiltrated.
So more overland flow + increases chances of flooding.
Drains + sewers take water directly and quickly to river which increases the flood risk.