1.3.1 flooding Flashcards
what is a drainage basin?
the area of land drained by the river.
what is a catchment area?
the area within the drainage basin.
what is watershed?
the edge of highland surrounding a drainage basin.
what is the source?
the beginning of the river.
what is the confluence?
the point where two rivers or streams meet.
what is a tributary?
a stream or smaller river that joins a larger one.
what is a river mouth?
the point where the river ends, usually at the sea.
what is precipitation?
any form of water or moisture that comes from a cloud, eg. rain
what is interception?
precipitation that doesn’t reach the soil and is intercepted by vegetation, leaves/branches, buildings and concrete before reaching the soil. it is only temporary and quickly evaporated.
what is infiltration?
water on the ground surface goes into soil and moves downwards.
what is groundwater flow?
the process by which water flows through rocks.
what is throughflow?
the movement of water downslope within the soil layer.
what is overland flow?
(surface run-off) the movement of water over the land surface when the ground is saturated or frozen or when precipitation is too intense for infiltration to occur.
what happens to cause flooding?
- water reaching the river channel quickly
- the river overflowing onto the floodplain
what are the reasons for flooding in terms of climate?
- climate (heavy rainfall)
- no infiltration and therefore water runs off the surface
- occurs after heavy rainfall (in britain it occurs after thunderstorms in summer)
- this causes a flash flood
- snowmelt happens quickly causing a flood
- the ground may still be frozen so no infiltration occurs
what does impermeable mean?
water cannot get through, eg. concrete or granite.
what does permeable mean?
water can get through, eg. sandstone
where is a flood risk greater in terms of geology?
where there is impermeable rock or soil.
what is relief?
the shape of the land around us.
what do steep slopes do to rainfall?
channel heavy rainfall downwards quickly into rivers due to gravity.
how does vegetation affect flooding?
- trees, wood and forests intercept rainfall and take it into their roots
- trees delay the time water gets into a river
- farmland helps water infiltrate the soil and delay the time water gets into the river
how does human activity affect flooding?
- deforestation means delay times are reduced. higher risk of flooding
- urban growth leads to more flooding
- tarmac and concrete on roads and pavements are impermeable so surface runoff is increased
- water gets into rivers faster
what is peak rainfall?
the time of highest rainfall.
what is peak discharge?
the time when a river reaches it’s highest flow.
what is lag time?
the time water takes to reach the river.
what is the base of a river?
the normal flow
what is the rising limb?
the rising water flow in a river.
what affects the rising limb?
- vegetation
- rock type
- slope
- situation (eg. urban or rural river)
what is a falling limb?
shows that water is reaching the river but in decreasing amounts.
