Factors influencing flood risk Flashcards

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1
Q

what are the human factors that influence flood risk?

A

-urbanisation
-deforestation
-agriculture

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2
Q

what are the physical factors that influence flood risk?

A

-precipitation
-geology
-steep slopes

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3
Q

why does precipitation cause flooding?

A

torrential rainstorms can lead to sudden flash floods as river channels cannot contain a large volume of water, steady rainfall over several days can also lead to flooding

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4
Q

why does geology cause flooding?

A

impermeable rocks encourage water to flow overland and into river channels, this speeds up water flow and makes flooding more likely

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5
Q

why does steep slopes cause flooding?

A

in mountain environments steep slopes encourage a rapid transfer of water toward river channels, this increases the risk of flooding

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6
Q

why does urbanisation cause flooding?

A

building on a flood plain creates impermeable surfaces such as tarmac roads, water is transferred quickly to drains and then into urban river channels, this rapid movement of water makes flooding more likely

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7
Q

why does deforestation cause flooding?

A

much of the water that falls on trees is evaporated or stored temporarily on leaves, trees also use water when they grow, when trees are removed much more water becomes available and increases flood risk

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8
Q

why does agriculture cause flooding?

A

in arable farming, soil is left unused and exposed to the elements, this can lead to more surface runoff, this increased if the land is ploughed up and down steep slopes, as water can flow quickly along furrows

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9
Q

what’s a hydrograph?

A

it shows how a river’s discharge changes in response to a precipitation event

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10
Q

peak rainfall

A

highest amount of rainfall per time unit

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11
Q

rising limp

A

shows how quickly the discharge rises after a rain storm event

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12
Q

lag time

A

the time difference between the peak rainfall and peek discharge

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13
Q

falling limb

A

shows the reduced discharge once the main effect of runoff has passed

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14
Q

base flow

A

the normal flow of a river when its water level is being sustained by a groundwater flow

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15
Q

bankfull discharge

A

will be drawn as horizontal line marking the level of discharge above which flooding will occur as the river will burst its banks

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16
Q

what factors create a short lag time?

A

-small basin size
-high drainage density
-impermeable rocks
-urbanisation
-steep slopes
-saturated soil
-heavy rainfall

17
Q

what factors create a long lag time?

A

-large basin size
-low drainage density
-permeable rocks
-forests
-gentle slopes
-dry soil
-light rainfall