FACTORS EFFECTING RIVER FLOOD RISKS

How does increased discharge cause river level to increase?
- High discharge=more water in channel. - Factors that increase discharge cause flooding.
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Human - land use: buildings
- Made from impermeable materials (e.g. concrete). - Impermeable tarmac roads. - Impermeable surfaces increase runoff and drains quickly take runoff to rivers - increases discharge quickly=greater flood risk.
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Human - land use: trees
- Trees intercept rainwater on their leaves, which then evaporates. - Trees also take up water from ground and store it. - Cutting down trees increases volume of water that reaches river channel=discharge increased=flooding more likely.
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Physical - prolonged rainfall
- Long period of rain = saturated soil. - Further rainfall cant infiltrate = runoff increased into rivers = discharged increased = flooding more likely.
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Physical - heavy rainfall
- Heavy rainfall = water arrives too rapidly for infiltration = a lot of runoff = discharge increased = increased risk of flood.
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Physical - geology (rock type)
- Clay soils and some rocks (e.g. granite and shale) are impermeable = runoff increased. - When it rains, discharge increased quickly, could cause flood.
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Physical - relief (change in height of land)
-If river is in steep-sided valley, water will reach river channel much faster because water flows more quickly on steeper slopes. - Discharge increases rapidly, increasing flood risk.
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Other cards in this set

Card 2

Front

Human - land use: buildings

Back

- Made from impermeable materials (e.g. concrete). - Impermeable tarmac roads. - Impermeable surfaces increase runoff and drains quickly take runoff to rivers - increases discharge quickly=greater flood risk.

Card 3

Front

Human - land use: trees

Back

Preview of the front of card 3

Card 4

Front

Physical - prolonged rainfall

Back

Preview of the front of card 4

Card 5

Front

Physical - heavy rainfall

Back

Preview of the front of card 5
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