GCSE Geography - Physical Landscapes in the UK

Paper 1

drainage basin

an area of land drained by a river and its tributaries with a boundary (watershed) which are usually hills or mountains

Upper course (9)

• lots of vertical erosion

• v shaped valleys

• low velocity

• shallow low discharge

• narrow channel

• large, angular rocks due to little weathering

• interlocking spurs

• waterfalls and rapids

• gorges

middle course (7)

• lateral erosion and deposition occurs

• smaller more rounded sediments

• higher velocity

• deeper and wider channel

• discharge increases, more tributaries

• meanders

• oxbow lakes

lower course

• flood plains

• levees

• lots of deposition

• highest velocity

• very deep and wide channel

• highest discharge

• fine silt and clay sediment

velocity of water

friction between the river bed and the water slows down the velocity of the river channel. In the Upper course because the river is very shallow, most of the water comes in contact with the riverbed, slowing the speed due to friction

Erosion (4)

• Abrasion: sediments scrape against river bed and bank wearing channel

• attrition: rocks and pebbles hit against each other, wearing down, becoming more round and smaller.

• hydraulic action: air is trapped in the cracks and high pressure from water causes the cracks to force apart and break

• solution: the river can be slightly acidic due to acid ran which slowly dissolves the rocks

transportation (4)

• solution: chemicals are dissolved in the river water

• suspension: particles and small rocks are lighy enough to float within the water

• saltation: pebbles and small rocks which are too heavy to be suspended bounce along the river channel

• traction: large rocks are rolled along the river bed

how interlocking spurs form

• in the upper course the water doesn’t have enough energy so it is not powerful so it can not erode the hard rock, only ther soft rock.

• this means that the river will re-route and curl around the hard rock

how waterfalls form (6)

• when the river flows over hard rock and soft rock, the soft rock underneath erodes more quickly

• overtime this creates a hangover and an undercut.

• the roational movement of the water quickens the erotion, forming a plunge pool of sediments

• the overhang collapses overtime due to gravity, the broken sediments helps deepend the plunge pool due to erosion

• erosion continues to erode the soft rock under the hard rock, forming an overhand again further upstream

• the continual process of the overhang collapsing causes the waterfall to retreat upstream, overtime forming a gorge. this process repeats

how do meanders form? (3)

• the water’s velocity is greater on the outside of the bend of the river which means lateral erosion occurs, leaving a river cliff

• on the inside of the river the velocity is low so the water loses energy as the river changes direction, depositing sediments

• erosion wears away a cliff on the outer edge of a bend and deposition creates a slip off slope on the inside of the bend

thalweg

• the path of the fastest water (if you were on a slide, where you would be flung off (outside of corners of the river)

how an oxbow lake is formed (3)

• in a meander as erosion occurs on the outside where the velocity is the highest and deposition occurs on the inside of the river where the velocity is the lowest

• the meander bends more and more until the neck is broken off, creating a straight tiver

• the old meander seperates from the main river as deposition occurs

how are flood plains formed (4)

• in the lower course there are many meanders

• when the river floods the water spills onto the surrounding land

• the river loses velocity and deposits its load called alluvium

• the flood plains are made from silts which makes it fertile so lots of farming takes place in the lower course

how are levees formed (3)

• levees are raised river banks

• form during a flood when a river overflows its banks so the water loses energy and the largest and heaviest sedimet is deposited first and finer sediment is carried downstream

• repeating flooding causes more sediment to be deposited at the river bank, overtime building up to form natural levees

how mudflats form

at the mouth of the river at the estuary the river water is slowed by the tides, so there is a large amount of deposition which creates mudflats and saltmarshes that overtime will become permanent habitats on the coastline

human factors that increase flood risk (3)

• urbanisation (imperable surfaces = surface runoff increases and decreases time taken for water to reach river) also increases flash flooding

• deforestation - reduces transpiration so more surface runoff and more time for rain to travel to river increasing risk of flash flooding

• river’s capacity. if the river is filled with rubbish or debris, the channel’s size will decrease so the river can carry less water so more likely to flood

physical factors that increase the flood risk (3)

• the rate and volume of precipitation, if there is a storm a large amount of rain will fall at a short amount of time so it will increase flash flooding downstream as it increases the discharge in the river

• geology, many imperamble rocks so the water can’t percolate into the soil and it is surface runoff increasing flash flooding

• topography, the shape of the land will determine how quick precipitation flows into the river.

storm hydrographs (6)

• peak precipitation

• rising limb - increase in discharge

• peak flow - maximum discharge

• lag time: time delay between peak rainfall and peak discharge

• falling limb - decrease of river discharge after peak discharge

• base flow - normal level of discharge in the river

different types of flooding (2)

• flash flooding: steep graph, lots of discharge in short amount of time, short lag time, intense storm, high and steep slopes, less vegetation

• subdued flooding: longer lag time, lower maximum discharge, as it is over the course of a few days because the ground is already saturated the soil can not take in any water so it runs straight to the river as surface runoff, low and gentle slopes less runoff, lots of vegetation to transpire water

what happens if we dont manage drainage basins (3)

• risk of flooding which can damage properties

• famers might lose crops or cattle drowning

• if factories flood workers might lose jobs leading to rise in unemployment

soft engineering strategies to reduce flooding

• floodplain zoning - constructing houses and buildings further from the river. - reduces damage to houses and facilities without altering the river, creates recreational land like football pitches near the river, can only be done for new decelopments, you cant reconstruct an existing town

• wetlands - vegetation is planted and legel protection to stop building on wetlands, - wetlands store river water and can flood when needed so no damage to houses, creates valuable habitats for river wildlife, it takes long timer for wetlands to establish and grow

hard engineering strategies to reduce flooding (4)

• dams - in the upper course to regulate river flow - valves control and release the right amount of water to avoid flooding, can generate electricity, visually unappealing, villages can be flooded to create a resevoir so people must move out of their homes

• embankments and levees - banks of river are built up in brick and concreate to increase channel capactiy - reduces lateral erosion, protects property on river front, looks unnatural and destroys habitats along the river bank

• dredging - rubbish and sediment are dug from the bottom of the river - widens the river channel and removes pollution from the water, doesnt alter the look of the river, cheap hard engineering strategy, takes time and must be done regularly

• channel straightening and flood relief channel - to bypass the meanders increase the speed of river flow - reduces flooding risk since water flows faster downstream, protects urban villages by directing flood water away, expensive and disruptive of natural habitats

flood management (5)

• sandbags in doorways

• temporary flood barriers act like temporary banks to increase rivers capacity

• roads are closed to reduce the risk of someone being swept away

• valuable possesions moved upstairs and locals told to stay inside and upstairs

• in the uk environmental agency monitors and distributes warnings when floods are likely so locals can prepare and evacuate