Rivers - Physical Flashcards

Question

What happens to the upper course in the cross profile change downstream?

Answer 1

- The river erodes its bed hydraulic action and abrasion. - As the river travels downstream it is joined by a number of tributaries - these increased the volume of water which gives the river energy which means more erosive power. - this allows it to cut a much deeper channel with increased distance downstream,

Answer 2

- becomes wider as the gradient becomes less steep as there is less vertical erosion

Answer 3

Lateral erosion is dominant, this erodes the river banks which makes the channel wider

Answer 4

There is a steep V-shaped cross profile - vertical erosion by the river is important, - creates a slope that weathered material from the valley sides can fall down. - rivers have their source in upland areas sonthe rock is harder. - weathering and erosion cannot have much impact and the slopes remain steep.

Answer 5

- The gradient is less steep, river begins to meander and erode into valley sides - rate of weathering also increases on the softer rocks. - the river uses more energy on lateral erosion so not as much weathered material is removed - this builds up the valley floor to give it a more gentle profile.

Answer 6

The river is passing through low lying country. Deposition from floods builds up the flood plain meanders migrate. This builds and widens the valley

Answer 7

- The volume of water in the river falls - The amount of eroded material in the water increases - The water is shallower eg on the inside of the bend - The river reaches its mouth

Answer 8

- They are fingers or projections in the hillsides, that alternate from either side of the valley and project into the valley floor - They are caused by fluvial erosion - Found in the upper course

Answer 9

- A steep gradient - Convex slopes - Separated by a narrow valley which is taken up the river channel - Freeze thaw weathering may occur on the slope scree

Answer 10

Its is where water falls down a vertical drop in the channel

Answer 11

1) . Softer rock is eroded by hydraulic action and abrasion, more than the hard rock creating a 'steep' in the river 2) . As water goes over the steep it erodes more and more of the softer rock 3) . A steep drop is eventually created, which is a waterfall.

Answer 12

1) . The hard rock is eventually undercut by erosion. It becomes unsupported and collapses. 2) . The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion, this creates a deep plunge pool. 3) . Over time, more undercutting causes more collapses. The waterfall will retreat leaving a steep-sided gorge.

Answer 13

- the river erodes downwards as boulders, stones and rock particles are bounced back and scraped along the channel bed. - as river cuts down, the steep sides are attacked by weathering. This breaks up and loosens the soil and rock - the loosended material slowly creaps doen the slope because of gravity and is washed into the river and carried away - the end result is a steep sided valley that has the shape of a V

Answer 14

1) . Meanders migrate over time across the valley floor, they may start to erode towards each other 2) . Gradually the neck of the meander narrows until it is completely broken through, usually during a flood. 3) . This forms a newer straightner channel, the old meander loops are cut off by deposition to form a ox bow lake

Answer 15

A wide flat area of marshy land on either side of a river and is found in the middle and lower courses

Answer 16

- meanders could migrate across the floodplain due to lateral erosion, when they reach the edge of a floodplain they erode the valley side which explains why is it wide - when the river floods it deposits silt, creating a vey flat floodplain

Answer 17

A raised river bed found alongside a river in its lower course

Answer 18

1) . During low flow conditions deposition takes place, raising the river bed and reducing the capacity of the channel 2) . When flooding occurs, water flows over the sides of the channel. The velocity of the river decreases quickly leading to deposition of sediment on river banks. 3) . After many floods the height of the banks can be raised forming levees

Answer 19

Transitional zones between river and coastal environments and are affected by wave action as well as river processes. - main river process is deposition

Answer 20

Where the land is not normally underwater becomed inundated.

Answer 21

When a river channel can no longer hold the amount of water flowing in it. Water over tops it and floods the adjacent land - the floodplain

Answer 22

Increase - Steady rainfall over a long period of time can lead to saturated soils and high river levels

Answer 23

Increase - Can lead to flash floods

Answer 24

Increase - Impermeable rocks such as shales and clay encourage water to flow overland and into river channels. - this speeds up water flow and makes flooding more likely

Answer 25

Increase - Building on impermeable surfaces such as tarmac roads leads to water being transferred quickly to drains and rivers and into river channels - this rapid movement of water makes flooding more likely

Answer 26

Increase- Water that falls in trees is stored in leaves and branches as it is good for their growth. - when trees are removed, water flows more rapidly to the river

Answer 27

Soil is left unused and exposed for a long period of time, this can lead to more surface run off. - this is increased if land is ploughed up and down steep slopes as water can flow quicker along furrows.

Answer 28

Total length of all the streams in the drainage basin ➗ total area of the drainage basin

Answer 29

Rainwater either in the river channel, in lakes or in the ground. Excess water is carried back to the sea by rivers

Answer 30

The volume of water passing a given point in a river at any moment in time. It is measured in cucmecs

Answer 31

More likely to cause flooding - as it encourages water to flow over and into the channel

Answer 32

Slow flooding down - as the rock has holes in it which will allow water to pass through

Answer 33

More likely to increase flooding - Can lead to sudden flash floods as river channels cannot contain the sheer volume of water

Answer 34

Will cause flooding- as the ground will become logged with water and there are no drainage systems to store it

Answer 35

Will cause flooding - as if it snows then melts the excess water could over flow the rivers - the ground could also freeze and therefore infiltration can't occur

Answer 36

Reduce risk of flooding- due to evaporation which means less surface water However, the land can be hard and dry which would result in water running over ground and into the channel

Answer 37

Reduce the risk of flooding - as soil absorbs the water | However it could dry up the land too much and lead to not being able to absorb water

Answer 38

Will cause flooding - as saturated soil increase surface run off into river channel

Answer 39

Cause less flooding - as there is more time for water to infiltrate and go down However, the water would still go down and could cause a flood at the bottem

Answer 40

Cause flooding - as water can flow down quicker

Answer 41

Cause flooding - when trees are removed much more water is available and transferred to river channels as there is no storage for the water ie leaves

Answer 42

Reduce the risk of flooding - as there are more trees to collect the water

Answer 43

Will cause flooding - Building on floodplains allows water to be transferred quickly to drains and then the channel

Answer 44

- It may have high tidal range - It may be very wide - It will have mudflats that are visible at low tides - It may have tidal bores - which are huge waves that funnel up the river

Answer 45

In the Cotswold Hills, about 50km north of oxford. Much of the town is on the flood plain of the river Cherwell, a tributary of the River Thames The population is 45,000

Answer 46

Has a history of flood - 1998&2007 = devastating flood affects included the railway station submerging, roads closed, more than 150homes and businesses were flooded, £12.5 million damage

Answer 47

A 2.9km earth embankment- built parallel to the M40 motorway to create a flood storage area; it holds 3 million cubic meters of water. Reduces flooding

Answer 48

The A361 road - the road plus improvements to the drainage basin has helped to prevent flooding

Answer 49

Flow control structures- specially designed openings that control the rate of flow downstream towards Banbury. Any excess water backs up behind filling up the reservoir rather than continuing towards Banbury.

Answer 50

- Hard engineering strategy - Dams are barriers which trap water in a lake (reservoir). Water can be released in a controlled way. - they are often multipurpose and can be used for recreation, H.E.P, water supply and flood prevention

Answer 51

Issues - often controversial people lose land and may have to move if the valley floods Costs - very expensive to build Benefits - can provide renewable energy, store water for when levels are low, effective at controlling water flow eg Elan Valley Dam

Answer 52

Hard engineering | - meanders are cut off to form a straight channel which may be lined with concrete

Answer 53

Issues - can lead to flooding, it can be unattractive, needs maintaining Benefits - speeds up water flow to reduce flooding in an area eg River Derwent

Answer 54

Hard engineering | - they are man made levees

Answer 55

Issues - if made of concrete blocks can make it look unattractive Benefits - allows river channels to hold up more water eg River Trent

Answer 56

Hard engineering | - a man made river built to bypass an urban area

Answer 57

Costs - expensive to build Benefits - during high flow, sluice gate allows water from the river to enter the relief channel to reduce flooding - can create recreational opportunities

Answer 58

- soft engineering | Restricts different land uses to certain locations on the floodplain

Answer 59

Issues - Difficult to implement, farmers may be inconvenienced Cost- Doesn't cost to implement, Benefits- reduces risk to high value land uses e.g. Hospitals

Answer 60

- soft engineering | Fields of grassy areas that are allowed to flood

Answer 61

Issues- Land cannot be used for anything else | Benefits- Reduces flooding elsewhere, creates wildlife habitat

Answer 62

- soft engineering | River levels and weather are monitored by the environment agency who issue warnings

Answer 63

Issues/cost - Cost of running Environment agency, insurance may increase and house prices decrease Benefits- Reduce damage by taking action Emergency service will also be prepared

Answer 64

Tree planting

Answer 65

Issues- Cost of trees, planting and maintenance | Benefits- Trees intercept rainfall and slows down transfer of water to the river channel

Answer 66

- Road A362 - will be open during a flood to avoid disrupting people's lives - reduced levels of anxiety and depression through fear of flooding

Answer 67

- a new biodiversity action plan habitat has been created with ponds, trees and hedgerows - part of the floodplain will deliberately allowed to flood if levels are high

Answer 68

- cost of scheme was about £18.5 million | - donors included environment agency and Cherwell district

Answer 69

its an important river in the north east of England. its source is in the pennine hills near cross fell

Answer 70

- its located close to forest in Teesdale in the river's upper course - it has formed due to a resistant band of ingenious rock, its hard to erode this tough rock which has formed a step in the long profile of the river -> high force waterfall - as the river plunges over the waterfall, it undercuts the weaker limestone forming an overhang. is eventually collapses and the waterfall retreats upstream to form a gorge.

Answer 71

- where streams carry coarse sediment they may develop alternating sequence of shallow, fast flowing sections called riffles, they develop between meander bends where a drop in velocity has led to deposition of coarser sediment. - the deeper, slower-moving sections called pools, they develop close to the outside bend of the meander.