River Processes

Unit 1: Dynamic Planet


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  • Created by: Aniqa
  • Created on: 17-01-11 21:14

Upper Course.

Load: Material carried by a river. 

 Erosion: wearing away the landscape.

Solution: where dissolved chemicals are carried.

Suspension: Tiny particles of sediment carried in the river's current.

Saltation: Smaller stones or pebbles picked up & dropped again. 'skipping' motion. 

Traction: large stones dragged along.

Abrasion: sand & pebbles are dragged along the river bed, or knock into by saltation, wearing away the bed. 

Attrition: rocks & stones wear away each other as the knock.

Solution: where alkali rocks like Limestone are dissolved in acid rainwater. 

Hydraulic action: fast-flowing water is forced into cracks, breaking up the bank overtime. 


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How Waterfalls are formed.

1. Occur when a river crosses a bed of more resistant rock.

2. Erosion of the less resistant rock underneath continues - undercutting the rock above it. River's energy creates a plunge pool.

3. Less resistant rock beneath is eroded more by abrasion and hydraulic action. Creates a Ledge, which overhangs and collapses. 

4. Waterfall takes up a new position leaving behind a steep valley or gorge. 

Weathering: breakdown of rocks in situ. This means it happens where the rock is. Rocks are broken by being chemically attacked & mechanically broken down. 

  • Biological: plant roots penetrate rocks in search of water. 
  • Physical: Physical forces break rock into pieces, freeze-thaw.
  • Chemical: Chemical change or decay of solid rock.
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Meanders: Middle course.

Meanders: have a Helical flow.

Sediment is deposited by slower currents. 

Continued erosion of Meanders can lead to Ox Bow lakes. 

Sheffield Floods, UK.

  • Prolonged rain:
  • Soil saturation:
  • Confluence of several rivers:
  • Physical landscape:
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Storm Hydrographs.

- The graph which shows how a river changes as a result of rainfall. It shows rainfall and discharge.

Time Lag: length of time between peak rainfall and peak discharge of the river.

Peak discharge: where river flows reaches a peak.

Falling Limb: where river discharge decreases. 

Rising Limb: as water reaches the river, the discharge increases.

Hard engineering: structures built to defend from flood water.

  • Build flood banks, Increase the size of the river channel, divert the river away from the city centre, increase the size of drains, increase maintenance budget. 

Soft engineering: adapt to flood risks, and allow natural processes to deal with rainwater. 

  • Flood proofing, Flood plain zoning, Flood prediction & warning. 


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