River Landscapes in the UK

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  • Created by: tobyf
  • Created on: 12-05-18 12:06
Describe the different courses of rivers
Upper: v-shaped valley, steep sides. Narrow, shallow channel. Middle: gentle sloping valley sides. Wider, deeper channel. Medium gradient. Lower: very wide, almost flat valley. Very wide, deep channel
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Why are the courses different?
Upper course: closest to source; lower course: closest to mouth. Rivers erode landscape, then deposit material elsewhere - they valley shape depends on whether erosion or deposition is the dominant process.
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Difference between vertical and lateral erosion?
Vertical erosion: deepens the river valley, making it v-shaped; dominant in upper course of rive; particles scraped along river bed. Lateral erosion: widens the valley during formation of meanders; dominant in middle and lower course
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What are the four processes of river erosion?
Hydraulic action: the force of water. Abrasion: eroded rocks scrape and rub the channel. Attrition: eroded rocks smash into each other, breaking into smaller fragments. Solution: river dissolves some types of rock (chalk/limestone)
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What are the four processes of river transportation?
Traction: large particles are pushed along river bed. Saltation: pebble-sized particles are bounces along the river bed. Suspension: small particles (silt/clay) carried along by water. Solution: soluble materials dissolve in water, are carried along
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Why does deposition occur?
Occurs when river slows down, because: volume of water falls, amount of eroded material increases, water is shallower (inside of a bend), or the river reaches its mouth.
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How are waterfalls and gorges formed?
River flows by hard rock, then soft rock. Soft rock eroded more than hard rock, creating wf. Hard rock under cut, becomes unsupported & collapses - material erodes softer rock, forming plunge pool. As this repeats, the wf retreats, forming gorge
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What are interlocking spurs?
At river's upper course, most erosion occurs vertically, creating v-shaped valleys. Rivers aren't powerful enough for lateral erosion, so they have to wind around hillsides. With hillsides that interlock with each other, the rivers wind around them.
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How are meanders formed?
The current is faster on outside of bend as channel is deeper, more erosion occurs forming river cliffs. The inside current is slower as it's more shallow, so eroded material is deposited on the inside of the bend, forming slip-off-slopes
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How are ox-bow lakes formed?
Erosion causes the outside bends to get closer, until there is only a small bit of land separating them. The river breaks through, causing the water to flow through the shortest course. Deposition cuts off the meander, forming an ox-bow lake
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Explain floodplains
Flood plains are wide valley floors which occasionally flood. When there is a flood, water slows down and deposits eroded material, building it up. Deposition on slip-off-slopes also builds it up. Meanders migrate across flood plains, making it wider
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How are levees formed?
During floods, the heaviest material is deposited closest to the river as it gets dropped first as the river slows. Over time, material builds up, creating levees along the edges of the channel, or natural embankments
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What are estuaries?
They're found the mouth of the river. The water here is tidal. The water floods over the banks carrying silt/sand onto the valley floor. As the tide reaches its highest, the slow water deposits more sediment. As mud builds up, mudflats are formed
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Along the River Severn, name a waterfall, meanders, floodplain/levees and estuary
Waterfall: "Severn Breaks its Neck". Meanders: near Ironbridge and Welshpool. Floodplain and levees: Gloucester. Estuary: Severn Estuary near Bristol
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Define peak discharge, lag time, rising limb and falling limb
Peak discharge: the highest river discharge. Lag time: delay between peak rainfall and peak discharge. Rising limb: increase in river discharge as rainwater flows into river. Falling limb: the decrease in discharge as river returns to normal level
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What factors increase chance of flooding?
Prolonged rainfall saturates soil. Heavy rainfall means water arrives too rapidly for infiltration, increasing runoff. Some rocks and soils are impermeable, so runoff is increased. Steeper valleys cause water to reach channel quicker
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How can land use increase flood risk?
Buildings are often impermeable, & are surrounded by impermeable roads. This increases runoff & ∴ risk of flooding. Trees intercept water & remove it from the ground - cutting them down increases water that reaches the river ∴ increasing discharge
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Name some hard engineering strategies for reducing flood risk
Dams are huge walls, reservoirs are formed behind them where water is stored. River's course could be straightened, reducing distance water travels. Embankments allow river to hold more water. If river's too high, can be diverted around certain areas
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Name some soft engineering strategies for reducing flood risk
Flood warnings allow evacuation & preparation. Buildings can be strengthened. Restrictions on building near floodplains (flood plain zoning). Planting trees to increase interception. Making the river more natural to lower risk downstream
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Cockermouth - location and reasons
Small town on the northern Lake District National Park border. Area is at risk from flooding due to steep mountains, thin soil, impermeable rock. Experienced flooding before - 1300 homes flooded and £100 million cost in 2009
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Cockermouth - management strategies
Glass panels, 53cm high to allow views and protection. Self closing barriers 1m high, 120cm long detect high water levels. Reinforced concrete walls allow water in, not out. Flood gates allow for no gaps in the river wall, easy dredging & crossing
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Cockermouth - positives & benefits
Flood walls fit in with Georgian character of town. River views not blocked. Self closing barriers operate on their own. Flood gates allow for dredging to deepen & widen channel so it can hold more water. People feel safe & have cheaper insurance
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Cocketmouth - limitations and conflict
Scheme took 4 years to complete. Flood walls overflowed & town flooded in 2015. Dredging can disturb wildlife and harm biodiversity. Some parts of the design don't keep in with town's character. Cost: £4.4 million
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Other cards in this set

Card 2

Front

Why are the courses different?

Back

Upper course: closest to source; lower course: closest to mouth. Rivers erode landscape, then deposit material elsewhere - they valley shape depends on whether erosion or deposition is the dominant process.

Card 3

Front

Difference between vertical and lateral erosion?

Back

Preview of the front of card 3

Card 4

Front

What are the four processes of river erosion?

Back

Preview of the front of card 4

Card 5

Front

What are the four processes of river transportation?

Back

Preview of the front of card 5
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