river discharge [hydrographs & flooding] Flashcards
(14 cards)
what do hydrographs show
how peak discharge changes over time in relation to rainfall
what is discharge
volume of water flowing per second
what is peak discharge
hightest discharge in the periodie time you are looking at
what is lag time
the delay between peak rainfall and peak discharge
what is the rising limb
increase of discharge as rainwater flows into river
whats falling limb
decrease in river discharge as the river returns to normal levels
what are the 4 physical factors that affect flood risk
- heavy rainfall
- geology
- relief of land
- prolonged rainfall
expalin heavy rainfall
water arrives to fast cannot infiltrate so lots of surface runoff = inc to discharge
explain geology
if rock type is impermeable like granite no infiltration will occur = inc surface runoff and discharge
explain relief
if there is a steeper grac=dient the water will flow faster down and into river faster = rapid inc of discharge
explain prolonged rainfall
= can saturate the soil [full] = so no more rainfall can infiltrate
= inc surgace runoff and inc discharge
what 2 human factors inc flood risk
- deforesation
- urbanization
explain deforestation
- trees intercept water on leaves which then evaopates & absorbs water from the gorund = dec suraface runoff if trees are removed = less of that occurs = inc discharge
explain urbanisation
building more infastructure such as roads [concrete] means an inc impermeable surgfaces less infiltration = inc of surface runoff = inc discharge
