AQA GCSE Geography - River Landscapes in the UK

what are the four types of river erosion?

hydraulic action

abrasion

attrition

solution

what is hydraulic action?

air becomes trapped in the cracks of the river bank and bed by the force of the water, and causes the rock to break apart

what is abrasion?

when pebbles grind along the river bank and bed

what is attrition?

when rocks that the river is carrying knock against each other, becoming smaller and more rounded

what is solution (erosion)?

when the water dissolves certain types of rocks

what are the four types of river transportation?

traction

saltation

suspension

solution

what is traction?

large, heavy pebbles are rolled along the river bed

what is saltation?

pebbles are bounced along the river bed

what is suspension?

lighter sediment is suspended within the water

what is solution (transportation)?

the transport of dissolved chemicals

what is deposition?

when a river loses energy and drops the sediments it has been carrying

what are the factors leading to deposition?

. shallow water

. reaching river's mouth

. when the volume of the water decreases

what is a drainage basin?

the area of land around a river that is drained by the river and its tributaries

what is the watershed?

area of high land forming the edge of a river basin

what is the source of a river?

where a river begins

what is the mouth of a river?

where the river meets the sea

what is a confluence?

a point at which two rivers meet

what is a tributary?

a small river or stream that joins a larger river

what is the river channel?

where the river flows

what is the long profile of a river and what does it show?

. a line representing the river from its source to its mouth

. it shows how the river changes over its course.

what is the river's load like in the upper course?

. often an upland area

. the river's load is large in the upper course, as it hasn't been broken down by erosion yet

what is the river's load like in the lower course?

. land is a lot flatter

. the river's load is fine sediment, as erosion has broken down the rocks

what is the cross profile of a river?

it is a cross-section of a river's channel and valley at a certain point along the river's course

what is happening in the upper course in a cross profile?

. as the river flows downhill there is an increase in vertical erosion

. the channel is shallow and narrow because there is not a lot of water in it

what is happening in the middle course in a cross profile?

. as the river flows into the middle course, there is some vertical erosion but more lateral erosion

. the channel is wider and deeper as a result

what is happening in the lower course in a cross profile?

. in the lower course there is a lot less erosion, with only some lateral erosion

. the channel is at its widest and deepest

what is a waterfall?

a sudden drop along the river course

what does the rock have to be like for a waterfall to form?

horizontal bands of resistant rock over exposed, less resistant rock

what is the process of the formation of a waterfall?

. the soft rock is eroded faster than the hard rock, creating a step

. erosion continues, hard rock is undercut forming an overhang

. abrasion and hydraulic action create a plunge pool

. over time this gets bigger, increasing size of overhang until hard rock is no longer supported and collapses

. process continues, waterfall retreats upstream

what is created by waterfall retreat?

a steep sided valley, called a gorge

what are interlocking spurs?

a series of ridges projecting out on alternate sides of a valley around which a river winds its course

how are interlocking spurs formed?

. in the upper course there is more vertical erosion

. the river cuts down into the valley

. if there are areas of hard rock which are harder to erode, the river will bend around them

. this creates interlocking spurs of land which link together

what are meanders?

large bends in a river

how are meanders formed?

. as a river goes around a bend, most of the water is pushed towards the outside, causes increased speed and increased erosion

. lateral erosion on outside bend causes undercutting of the bank to form a river cliff

. water on inner bend is slower, causing water to slow down and deposit eroded material, creating a gentle slope of sand and shingle - a slip-off slope

what are oxbow lakes?

curved lake formed from a meander cutoff

how are oxbow lakes formed?

. erosion narrows neck of land within meander, as the process continues meanders move closer together

. when there is a very high discharge the river cuts across the neck, taking a new, straighter and shorter route

. deposition will occur to cut off the original meander, leaving a horseshoe-shaped oxbow lake

what is a floodplain?

an area of land which is covered in water when a river bursts its banks

how do floodplains form?

. erosion removes any interlocking spurs, creating a wide, flat area on either side of the river

. during a flood, material being carried by the river is deposited

. over time, the height of the floodplain increases as material is deposited on either side of the river

what are floodplains used for?

agriculture due to high fertility

what are levees?

natural embankments along the edges of a river channel

how are levees formed?

. sediment is transported downstream.

. when the river floods, the sediment spreads out across the floodplain

. as the river loses energy, the largest material is deposited first on the sides of the river banks and smaller material further away

. after many floods, sediment builds up to increase the height of the river banks

how are levees helpful?

they mean that the channel can carry more water and flooding is less likely to occur in the future

what is an estuary?

the tidal mouth of a large river, where the sea meets the river

what do rivers form at estuaries?

. when the sea retreats the volume of the water in the estuary is reduced

. the river deposits silt to form mudflats which are an important habitat for wildlife

where is the river tees located?

. north of England

. source is located in the Pennines

. flows east to its mouth where the river joins the North Sea

what is the upper course of the river tees like?

. it has hard impermeable rocks.

. vertical erosion has formed a V-shaped valley

. High Force, the UK's largest waterfall by volume when in full flow is located in the upper course

what is the middle course of the river tees like?

. as the river starts to erode sideways it forms meanders

. these can be identified in the middle course near Barnard Castle

what is the lower course of the river tees like?

. near Yarm, the meanders are much larger, and oxbow lakes have formed.

. there are also levees which have formed when the river has flooded

. very large estuary with mudflats and sandbanks which supports wildlife in the area

. sites such as Seal Sands are protected areas

what are some causes of flooding?

. prolonged rainfall - if it rains for a long time, the land around a river can become saturated

. heavy rainfall - if there is heavy rainfall there is less chance of it being soaked up by the soil

. relief - steep valley is more likely to flood than flatter valley

. geology - permeable rocks allow water to pass through pores and cracks, impermeable rocks do not

. vegetation - trees and plants absorb water, interception

. urban land use - area surrounding a river built on, an increase in impermeable surfaces

what does a hydrograph show?

how a river responds to a period of rainfall

what is the peak discharge on a hydrograph?

maximum amount of water held in the channel

what is the peak rainfall on a hydrograph?

maximum amount of rainfall (millimetres)

what is the lag time on a hydrograph?

the time taken between peak rainfall and peak discharge

what is the rising limb on a hydrograph?

shows the increase in discharge on a hydrograph

what is the falling limb on a hydrograph?

shows the return of discharge to normal

what is the base flow on a hydrograph?

the normal discharge of the river

what are some factors influencing lag time?

size of drainage basin

vegetation

valley side steepness

soil type

what strategies are used to reduce flooding?

hard and soft engineering

what are dams and reservoirs?

hard engineering strategy

the dam traps water, which builds up behind it, forming a reservoir

water can be released in a controlled way

what are some advantages of dams and reservoirs?

can be used to produce electricity by passing the water through a turbine within the dam

reservoirs can attract tourists

what are some disadvantages of dams and reservoirs?

very expensive

dams trap sediment which means the reservoir can hold less water

habitats are flooded often leading to rotting vegetation which releases methane

settlements are lost leading to the displacement of people

what is river straightening and dredging?

hard engineering strategy

straightening the river speeds up the water so high volumes of water can pass through an area quickly

dredging makes the river deeper so it can hold more water

what are some advantages of river straightening and dredging?

more water can be held in the channel

can be used to reduce flood risk in built-up areas

what are some disadvantages of river straightening and dredging?

dredging needs to be done frequently

speeding up the river increases flood risk downstream

what are embankments?

hard engineering strategy

raising the banks of a river so that it can hold more water

what are some advantages of embankments?

cheap with a one-off cost

allows for flood water to be contained within the river

what are some disadvantages of embankments?

looks unnatural

water speeds up and can increase flood risk downstream

what are flood relief channels?

hard engineering strategy

the floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course

what are some advantages of flood relief channels?

removes excess water from the river channel to reduce flooding

what are some disadvantages of flood relief channels?

expensive to build

if water levels continue to rise, the relief channel may also flood

what are flood warnings and preparation?

soft engineering strategy

the environmental agency monitors rivers and issues warnings when areas are likely to flood so people can prepare

what are some advantages of flood warnings and preparation?

people have time to protect their properties, eg with sandbags

many possessions can be saved, resulting in fewer insurance claims

what are some disadvantages of flood warnings and preparation?

some people may not be able to access the warnings

flash floods may happen too quickly for a warning to be effective

they do not stop land from flooding

what is floodplain zoning?

soft engineering strategy

allowing only certain land uses on the floodplain reduces the risk of flooding to houses and important buildings

what are some advantages of floodplain zoning?

more expensive buildings and land uses are further away from the river, so have a reduced flood risk

less damage is caused, leading to fewer insurance claims

what are some disadvantages of floodplain zoning?

not always possible to change existing land uses

planners have to decide what type of flood to plan for

what happened to cause the 2004 flood in boscastle, Cornwall?

a month's worth of rain fell in two hours

what factors contributed to the flash flood in boscastle?

the drainage basin of Boscastle is steep and impermeable rock

Boscastle is also located on a confluence of three rivers

how much did the environment agency invest in boscastle to present future floods?

£10 million

what were the flood management strategies implemented in boscastle?

widening and deepening the river channel - so the river can carry more water

removing low bridges and replacing them with wider bridges - so larger amounts of water can flow freely

raising car park and using permeable surface - less surface runoff

tree management - dead trees removed to prevent them being swept away, causing blockages under bridges