Processes of erosion
- Attrition - material is moved along the river bed, collides with other material and breaks into smaller pieces.
- Abrasion - fine material rubs against the river bank, the bank is worn away by a sandpapering action.
- Solution - rocks from the banks and the river bed are dissolved by acids in the river.
- Hydraulic action - the sheer force of the water hitting the river banks.
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Processes of transportation
- Traction - large rocks are rolled along the river bed.
- Saltation - smaller stones are bounced along the river bed.
- Suspension - small grains of sand are carried in the water.
- Solution - material is dissolved and carried downstream.
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The Finer --> The Fragments --> The Futher --> They Flow.
Deposition occurs when a river can no longer support material.
Material is put down when the river no longer has the energy to carry the load.
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River Basin/Drainage Basin
- Watershed - a boundary that separates drainage basins.
- Main channel - the main river.
- Confluence - Where the tributary meets with the main channel.
- Tributary - a small stream flowing into the main channel.
- Mouth - where the river meets the sea.
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Factors affecting discharge
- Slope/relief - the steeper the slopes, the faster the runoff, so more water in the river.
- Rock type - impermeable rock will mean a surface runoff.
- Soil - thin soil, less infiltration. Deeper soil, more infiltration.
- Land use - rural areas with little tarmac/concrete or drains there will be a higher level of infiltration.
- Precipitation - more intense rain, the shorter the lag time/more rain in the river.
- Temperature - in the summer, dry soil, longer lag time as rain infiltrates. In the winter, frozen or saturated soil, shorter lag time as water cannot infiltrate so runs off quickly.
- Previous weather - large amounts of rain, saturated soil, cannot allow any more infiltration so run-off increases.
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Flood Defence Schemes - Hard Engineering
- Dams and Reservoirs - used to save/manage the flow of excess water. Some are used to generate hydropower.
- Man-made Levees - stop water flooding over. Commonly used in rivers near the sea.
- Straightening Meanders - Involves digging a shorter channel. This can cause flooding downstream.
- Dredging Channels - Can allow importing and exporting. But can cause a mess in the sea traffic.
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Flood Defence Schemes - Soft Engineering
- Do nothing - The natural habitat is left, doesn't interfere with the rivers flow, it's cheaper to maintain.
- Flood warnings and preparation - Buildings will be saved and people will be prepared. However unexpected floods will mean the equipment won't be available.
- Floodplain zoning - Identifies areas of varying flood hazards.
- Re-afforestation/plant tree - Replacing of forests and woodlands that have been destroyed. Trees intercept the rain and slow down the run-off to the river.
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