River processes and landorms

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What is mechanical weathering?
physical changes causing rocks to break down
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What is discharge?
the volume of water in a river passing a point in a given time
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What is lateral erosion?
the wearing away of the landscapes when a river erodes sideways
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What is a long profile?
a section of the course of a river drawn from the source to the mouth
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What is vertical erosion?
the wearing away of land in a downwards direction
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What are the factors leading to deposition in a river?
shallow water, end of the rivers journey, when volume of water decreases
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Describe the upper course
It has steep slopes which increases the velocity of the river when discharge is high, the channel is narrow and shallow,it has a large load
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What does high discharge in the upper course lead to?
High vertical erosion, meaning erosion of riverbed and large sediment is transported due to traction
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Describe the middle course
The gradient is less steep, the channel becomes deeper and wider and sediment gets smaller in size,more lateral erosion
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Describe the lower course
The sediment in the load is fine and the channel is at its widest and deepest
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What are the causes of flooding?
prolonged rainfall,relief,geology,vegetation and urban land use
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What is infiltration?
when the water is absorbed by the soil
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How does prolonged rainfall cause flooding?
the land becomes saturated, if there is more rainfall later it cannot be soaked up so its runs along the surface
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How does relief cause flooding?
a steep valley is more likely to flood than a flatter valley because the rainfall will run off into the river more quickly
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How does geology cause flooding?
permeable rocks allow water to pass though the pores, whereas impermeable rocks don't
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How does urban land use cause flooding?
when an area is built on with tarmac and concrete (impermeable surfaces) then it cause surface run off
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How does vegetation cause flooding?
trees and plants absorb water during interception
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What is the peak discharge?
the maximum amount of water held in the channel
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What is peak rainfall?
the maximum amount of rainfall
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What is the lag time?
the time taken between peak rainfall and peak discharge
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What is the rising limb?
the increase in discharge
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What is the falling limb?
the return of discharge to normal flow
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What is the base flow?
the normal discharge of water
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What factors affect lag time?
geology,soil type,slope,shape of drainage basin,antecedant conditions and vegetation
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How does soil type affect lag time?
clay soils do not drain easily and become saturated very quickly, meaning no more water can be absorbed and lag time is shorter
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How do slopes affect lag time?
Steep slopes lead to rapid water transfer leading to shorter lag time
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How does the drainage basin shape affect the lag time?
High density water basin means more streams and rivers which speeds up water transfer and shortens lag time
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How do antecedant conditions affect lag time?
wet conditions before a storm can cuase ground to become saturated which speeds up overland flow and shortens lag time
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What do dams and reservoirs do?
dams trap water, which therefore builds up behind it forming a reservoir
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What are the advantages of dams and reservoirs?
can produce electricity by passing water through a turbine, reservoirs can attract tourists
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What are disadvantages of dams and reservoirs?
They are very expensive, dams trap sediment which reduces volume of water that reservoir can hold,habitats are flooded leading to rotting vegetation and methane being released,settlements are also lost
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What does river straightening do?
speeds up the water so high volumes of water can pass through an area quickly
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What does dredging do?
makes the river deeper so it can hold more water
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What are the advantages of river straightening and dredging?
more water can be held in the channel and they can be used to reduce flood risk in built up areas.
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What are the disadvantages of river straightening and dredging?
dredging needs to be done frequently and speeding up the river increases flood risk down stream
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What do embankments do?
raise the banks of the river meaning it can hold more water
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What are the advantages of embankments?
they are cheap, allow for flood water to be contained within the river
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What are the disadvantages of embankments?
water speeds up and can cause an increased flow risk down stream
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What do flood relief channels do?
cause floodwater to flow into them, and is taken to an area where it can be absorbed or re-enters the river further down its course
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What are the advantages of flood relief channels?
removes access water from the river channel to reduce flooding
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What are the disadvantages of flood relief channels?
they are expensive to build, and if water levels continue to rise the relief channel may also flood
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What are flood warnings?
environmental agencies monitor the river and issue warnings
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What are the advantages of flood warnings?
people have time to protect their properties, possessions can be saved, resulting in fewer insurance claims
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What are disadvantages of flood warnings?
some people may not have access to warnings, flash floods happen to quickly,they don't stop flooding just warn people
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What is floodplain zoning?
allowing only certain land uses on the floodplain reduces the risk of flooding houses and more important buildings
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What are advantages of floodplain zoning?
more expensive buildings and land uses are further away from the river, so they have reduced flood risk, less damage caused, fewer insurance claims
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What are the disadvantages of floodplain zoning?
its always possible to change existing land uses
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Other cards in this set

Card 2

Front

What is discharge?

Back

the volume of water in a river passing a point in a given time

Card 3

Front

What is lateral erosion?

Back

Preview of the front of card 3

Card 4

Front

What is a long profile?

Back

Preview of the front of card 4

Card 5

Front

What is vertical erosion?

Back

Preview of the front of card 5
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