rivers gcse geography

freeze thaw, water gets into cracks, feezes and widens the crack

roots of plants grow in cracks

acid is present in rain which reacts with minerals in rocks to dissolve them

gravity pulls rock matter down a slope

the river erodes the bottom of a valley slope whcih cases material above to slide downwards specifically if saturated in water

large boulders roll along the river bed

smaller pebbles bounced along the river bed

finer particles of sediment suspended in the water giving river a brown appearence

dissolved minerals in the river stream e.g chalk

where a river starts

where a river joins the sea

the makeup of a river as it flows

amount of water in a river

steepness of a river

upper course

steep gradient, small discharge, shallow, narrow with steep sides, large angular boulders of sediment

upper course

upper course

less steep gradient, large discharge, deep, flat steep sides, fast, rounded rocks transported through saltation

middle and lower course

middle and lower course

shallow gradient, very large discharge, deep, flat riverbed with gently sloping sides, smooth rounded pebbles with saltation

lower course

lower course

it becomes impermeable due to snow covering it making areas with rivers prone to flooding

the top layer bakes causing it to be impermeable and increased surface runoff directing water into rivers

where water of low energy and low discharge flows around ridges in the valley of hard rock causing the stream to form a zig zag pattern, found in the upper course of a river

where a river undercuts hard rock through hydraulic action forming a plunge pool and making a waterfall

a steep sided valley where a waterfall once was, usually having a river running through it, its what a waterfall leaves behind as it retreats

area around the river that is prone to flooding, layers of aluvium are deposited here when the flood looses energy building the floodplain up

the embankments on the side of rivers naturally created by the deposiotion of heavy sediment during a flood, building the river bank up

lateral (sideways) erosion causing large bends to form called meanders, material is eroded on the outer edge where the current is greatest creating a river cliff, this material gets deposited on the inner edge causing point bars

where the lateral erosion of a river causes the river bank to be undercut causing a small cliff

the neck of a meander is slowly eroded as the water takes the quickest route, deposiotion seals off the meander, an oxbow lake is left and completely dettatched from the meander

water cannot penetrate/ infiltrate rocks

where water is unable to saturate into the ground so it sits on the surface

the steepness of a valley, steeper valleys will flood faster as water moves with more velocity

citys full of impermeable rock e.g concrete are built meaning water cannot seep through rocks and it just sits on top, more houses are built on flooplains changing the natural landscapes

there are less trees to intercept the rainfall which helps to reduce surface run off removing them means water reaches rivers quicker

the sediment from the fiekds being ploughed increases the amount of sediment eventually ending up in rivers heightening the risk of flooding

pollute them with chemicals, use the water up

rainfall intensity, geology, snowfall, drainage basin

lots of rain falling preventing infiltation

land may consist of less permeable rocks than others causing water to sit on the top of the land

warmer temperatures in cold climates melt snow causing a higher volume of water and more discharge in the river

an increase in tributaries leading to a river may casue it to flood due to more discharge

man made structures acting as defenses to prevent rivers flooding

barries constructed to hold back water in artificial lakes. pros= long-lasting, can be used to generate hydroelectric power, can store large volumes of water. cons= expensive, sediment can build up over time, floods the original landscape

deepening or widening the river channel replacing the natural meanders and flooplain. pros= allows water to flow quickly away from areas of flood risk. cons= ugly, more water is taken downstream increasing the flood risk to settlements

making a river taller to increase the dishcharge its able to hold. pros= one off cost, flood water is contained in channel. cons= unnatural, water speeds up causing more issues downstream

use of natural processes to reduce the impacts of river flooding

where areas near the river (floodplains) are not able to be built on. pros= reduces homes flooding, allows infiltration, protects and preserves natural floodplain. cons= limits settlement growth

deliberate flooding in order to prevent thje river flooding to more important areas. pros= creates area for flood to go, allows for natural processes, preserves floodplains. cons= limits use of land

warning people about the floods coming. pros= effective and gets the message across, reduces insurance claims as people know what to expect. cons= dont do anything about the flood, may be too late

graph showing how a river reacts to prolonged amounts of rainfall

maximum amount of water held in the channel

maximum amount of rainfall (millimetres)

the time taken between peak rainfall and peak discharge

shows the increase in discharge on a hydrograph

shows the return of discharge to normal/base flow on a hydrograph

the normal discharge of the river