G Water On The Land

Question 1

What are levees (2)

Answer 1

Raised banks along course of river

Formed naturally made of transported material by river or artificially

Question 2

Explain formation of levees (4)

Answer 2

During periods of high rainfall and discharge river burst its banks and loses energy
River can no longer carry material transporting so deposition occurs largest material carried left behind first
Thick sediment deposited at channel edge
Thin over outer part of floodplain
Occurs many times causing levees to build up bigger along course of channel

Question 3

What is river flooding (2)

Answer 3

When river overflows

And spills onto floodplain

Question 4

One physical cause of flooding (2)

Answer 4

Heavy rain

Infiltration cannot occur rapid surface run off

Question 5

Explain how hard and soft engineering strategies help to manage risk of flooding in areas such as Boscastle (8)

Answer 5

Hard
River bank widened to increase capacity so reduce risk of flood
Jordan
River wall and lowered road means theres area for water to spill reducing flood risk
Car park raised
Soft
Tree
Positioning of car park next to ricer less important land use placed next to river less sig if flood
Salmon

Question 6

Describe how shape of river valley changes downstream (4)

Answer 6

Source 
V shape
Steep valley
River take up more of narrow valley floor
Middle
Broad 
U 
Lower gentler sides
Wider
Mouth
Flat wide

Question 7

How cross profile change downstream (3)

Answer 7

Near source narrow stop sided relatively deep valley
Downstream wider less deep valley sides less steep
Near mouth valley broad sides long way for river gentle low lying

Question 8

Waterfall features (3)

Answer 8

V shaped
Plunge pool
Steep drop

Question 9

Formation of waterfall (4)

Answer 9

Hard rock over soft, eroded mainly by hydraulic and abrasion faster cause overhang to develop
Overhang too heavy collapse into plunge pool which enlarges due to continued erosion
Continues to fall water retreats upstream leaving step sided gorge of recession

Question 10

Compare hydrographs (3)

Answer 10

High peak
Lag time
Gradient of rising and falling limb
Flashy

Question 11

Why hydrographs different(4)

Answer 11

Relief steeper rapid surface run off reduce time to get to stream flashier
Impermeable cannot soak in flow over land
Lack of vegetation in drainage basin no interception rots not take up water rapid run off shorter lag time

Question 12

How water demand met in UK (8)

Answer 12

Some areas have more water than they need (surplus); some have too little (deficit). These are areas of water stress and there needs to be transfer from areas of surplus to deficit. This means storing water in these areas a dams and reservoirs. Water can be long distance via aqueducts and pipelines. More and more local areas try to store enough water as this saves cost of transfers. Water companies try not to waste water in transfer and so pipelines need repairing when there are signs of leaks. This is expensive and currently, smaller, local schemes are important. As well as trying to get water where it is needed, people try not to waste water and new fittings in houses can try to conserve water such as washing machines that use less water; dual flush toilets and having systems installed that will recycle water used in the home
Wales lake vrynwy Liverpool

Question 13

How river erodes (4)

Answer 13

Hydraulic action force of water against bed and banks more effective when river in high flow air bubbles forced into cracks can suddenly collapse and vibrations caused weaken rocks
Abrasion load carried hit banks lateral and vertical erosion material break off occurs especially when discharge high
Attrition reduction in size of load itself as it knocks into other items of material load bits break off
Solution certain rock tunes like limestone and chalk dissolved by slightly acidic rainwater. Rate depends in water acidity and temp

Question 14

Ox bow lake formation (4)

Answer 14

River erodes laterally forms meanders
Outside bend water flows faster so erosion
So outside bends move closer together and meander necks narrower swan neck meander
Flood high discharge river cut across rivers and take straight ciyrse
Old course of river channel becomes ox bow lake
Lake dries form meander scar

Question 15

Why rivers flood (3)

Answer 15

Town on floodplain impermeable not infiltrate rapid surface run off reduce lag time
No vegetation not interception roots not take up water rapid run off

Question 16

Benefit of hard and soft engineering (8)

Answer 16

Widening of river bank and build wall river can hold more water, less likelihood of flooding. Dams and reservoirs: hold back water to control flooding people’s lives and their property should be safe, people not live in fear of flooding or losing family and friends. (Three Gorges Dam has reduced risk from 1 in 10 years to 1 in 100 years), many dams and reservoirs are multipurpose projects (help flood control, water supply and irrigation). It is more immediate than strategies like planting trees that take a long time to grow. Warning systems may save people’s lives, but their property is damaged and their possessions lost not good way of managing floods. They will be able to prepare but will suffer much more than if a dam had been built. Floods can still happen with dams and people may not be prepared if they are not warned Straightening and deepen: speed up the flow, or line it with concrete. Dredge the river to make it deeper and able to carry more water

Flood warnings and preparation: warning people of floods is useful as they can prepare, taking their possessions to higher floors. Environment Agency monitors river levels and rainfall, use this and weather forecast to predict areas at risk of flooding Floodplain zoning: land next to the river less important land uses are placed next to the river and so it is less significant if these areas flood, no buildings. pasture for grazing, fields, car parks, industry then house. Do nothing: let natural processes occur, in rich, money can be saved in non-flood years for when a flood strikes. When river floods, eroded material deposited on floodplain making it more fertile which is an advantage, but doing nothing a lot of damage caused and the risk flooding not reduced. planting trees slows down the speed of the water and reduces flooding. This tries to help slow down the water cycle in a natural way.

Question 17

How river transports load (4)

Answer 17

Traction large material dragged along bed
Saltation smaller pebbles bounce a,one bed hopping motion
Suspension fine material carried in water itself floats
Solution some rocks soluble dissolve like limestone invisible dissolved

Question 18

Floodplain formation (4)

Answer 18

Flat area adjacent to river channel especially in lower course natural area for rivers to flood. Form due to both erosion and deposition. Erosion widens the valley taking away the interlocking spurs present nearer the source and creating wide, flat river. Lateral erosion caused by meanders and area next to the slip off slope provide slow migration downstream to widen flood plain. Deposition on slip off slope provide sediment to build up valley floor. When the river overflows, material being it up speed is lost. over time, this sediment forms layers on the flood plain, building it up

Question 19

Case study responses to flooding (8)

Answer 19

Cumbria The government provided £1 million to help with the clean-up and repairs and agreed to pay for road and bridge repairs in Cumbria, the Cumbria Flood Recovery Fund was set up to help victims of the flood. It reached £1 million after just 10 days, Network Rail opened a temporary railway station in workington, the visit cumbria’ website provided lists of recovery services and trades, and people who could provide emergency accommodation.
Bangladesh: supply food, medicines and blankets to survivors. Local people rebuild their homes. began to the An emergency appeal was launched for S74million by UN had posters displaying risks of drinking flood water and they tried to supply water purification tablets. In the longer term, ways of warning people were looked at so that there would be fewer deaths and the provision of flood shelters. Here, raised areas are identified where people can move with their cattle and dried food is available. Clean water is obtained before flooding. World Bank loaned money for the repair of roads to help with education, following loss of many schools.

Question 20

Factors affecting discharge (6)

Answer 20

Amount and type of rainfall: more rain, saturate soil and underlying rock. In drizzle, more time for water to infiltrate, freeing more space for rain Temperature: higher, more evaporation and transpiration, river levels go down
Previous weather conditions: if it has been dry, rain will soak into the ground and will be slow to reach the river.
Prolonged rain: rain for a long period of time means that the ground will be saturated and infiltration will not be able to occur, causing rapid surface runoff. Heavy rain ground cannot soak up the rainfall quickly enough.
Snowmelt: frozen ground less infiltration
Relief: The amount of water will be high if the river is in an area with steep slopes. This will cause the water to nun quickly over the surface due to gravity (by surface runoff, before it has time to soak in it will reach the river quickly and the amount of water will increase.
Rock type: areas of impermeable rock will have more water in them as they do not allow water to soak in, so water flows quickly over the surface to the channel. In contrast, rocks like limestone have joints and bedding planes that provide pathways for river, so enter and go through, so water is removed from the surface and takes a slower route to the river so there is less water route present in the channel.
Land use lack of vegetation in drainage basin, no interception, roots do not take up water so runoff is rapid. Deforestation, less infiltration, water reach ground faster. urbanisation/bulding construction, expanding towns, impermeable surface, overland flow, drains take water quickly into river channel, reduce lag time.

Question 21

Why area suitable for dams and reservoirs (2)

Answer 21

Mountainous low lying areas have rivers
High up more rain
Pop density low less disruption

Question 22

Issues building dams and reservoirs (8)

Answer 22

Social: At Carsington, people lost homes and livelihoods when River yrynwy was created, the village of Llanwyddyn was flooded, people were forced to move as 10 farmhouses, 37 houses, 2 chapels and 3 pubs were drowned, taking away the whole community. Many parts of Wales have more water than they need so water stored in reservoirs like River Vrynwy s used to supply cities like Liverpool, local object to seeing it as their water.
Economic: dam built, £107m -to meet increased demand for water for increased use for things like washing machines.
Environmental: loss of land and habitat, impact on the flow of the river and impact of new uses such as recreation and tourism; reduction of flood risk.

Social: The Three Gorges dam benefit over 15 million people living in high-risk flood areas, At least 14 million people were forcibly moved from their homes to accommodate the dam. These displaced people were promised compensation for their losses, but many not received this $30 million of the funds set aside taken by corrupt local officials.
Economic: constructed at Yichang on the River Yangtze, S25.5b.
Environmental: The capacity of the reservoir should reduce the risk of flooding downstream from a 1 10 year event to a 1-in-100-year event. Protect over 25,000ha of farmland. Yangtze used to carry over 500 million tonnes of silt every year, up to 50% of this is now deposited behind the dam waste storage capacity of reservoir water heavily polluted from shipping, factories and discharged from cities-Chongqing pumps in over 1b tonnes of untreated sewage/yea