After a long period of rain, the soil becomes saturated. Any further rainfall can't infiltrate, which increases runoff into rivers. This increases discharge quickly, which can cause a flood.
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Heavy Rainfall - Physical
Heavy rainfall means there's a lot of runoff. This increases discharge quickly, which can cause a flood.
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Relief - Physical
Relief is how the height of the land changes. If a river is in a steep-sided valley, water will reach the river channel much faster because water flows more quickly on steeper slopes. This increases discharge quickly, which can cause a flood.
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Snowmelt - Physical
When a lot of snow or ice melts it meaqns that a lot of water goes into a river in a short space of time. This increases discharge quickly, which can cause a flood.
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Geology (Permeable Rock) - Physical
When a river is in an area of permeable rock (limestone), more water percolates into the rock instead of flowing on the surface. This means there's less runoff, so the risk of flooding is lower.
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Geology (Impermeable Rock) - Physical
When a river is in an area of impermeable rock (clay), water doesn't percolate into the rock but flows on the surface. This means there's more runoff, so the risk of flooding is higher.
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Deforestation - Human
Trees intercept rainwater on their leaves, which then evaporates. Trees also take up water from the ground and store it.
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Deforestation 02 - Human
This means cutting down trees increases the volume of water that reaches the river channel, which increases discharge and makes flooding more likely.
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Building Construction - Human
Buildings are often made from impermeable surfaces (concrete), and they're surrounded by roads made from tarmac (also impermeable).
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Building Construction 02 - Human
Impermeable surfaces increase runoff and drains quickly take runoff to rivers. This increases discharge quickly, which can cause a flood.
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Other cards in this set
Card 2
Front
Heavy rainfall means there's a lot of runoff. This increases discharge quickly, which can cause a flood.
Back
Heavy Rainfall - Physical
Card 3
Front
Relief is how the height of the land changes. If a river is in a steep-sided valley, water will reach the river channel much faster because water flows more quickly on steeper slopes. This increases discharge quickly, which can cause a flood.
Back
Card 4
Front
When a lot of snow or ice melts it meaqns that a lot of water goes into a river in a short space of time. This increases discharge quickly, which can cause a flood.
Back
Card 5
Front
When a river is in an area of permeable rock (limestone), more water percolates into the rock instead of flowing on the surface. This means there's less runoff, so the risk of flooding is lower.
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