RIVERS: Flooding
- Created by: Thea Tuckey
- Created on: 19-12-17 09:32
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- RIVERS: FLOODING
- CAUSES
- Human
- Deforestation
- Increased surface runoff
- Deforestation
- Physical
- Steep Relief
- Narrow Valleys
- Long periods of rain
- Wet, saturated soil
- Confluence (2 rivers joining)
- Heavy rainfall
- Snow melt
- Cold Temperatures
- Small basin
- Lack of Vegetation
- Large volumes of water reaching the channel & exceeding its capacity
- Any factor decreasing lag time = increasing peak discharge over channel capacity.
- Faliure of Defence
- Human
- DEFINITION
- Flooding occurs when the rivers discharge exceeds the channels capacity and overflows its banks and surrounding land.
- MANAGEMENT
- Hard Engineering
- Using technology/construction to control or prevent flooding.
- Dams
- Control river discharge.
- Expensive/Interrupts in river ecosystem & river processes
- Levees
- Increases channel capacity
- If fail - trap flood water = more damage/expensive
- Channel straightening and lining
- Increases efficiency
- Expensive/Break from ecosystem/increase flood risk downstream
- Flood Relief Channel
- Increase Channel capacity
- Uses land/Expensive
- Dredging
- Increase channel capacity
- Environmental Damage
- Soft Engineering
- Using natural processes to reduce the severity of flooding.
- Land Management
- Aforestation
- Increasing infiltration rates; reducing surface runoff; increasing lag time
- By afforesting 5% of land, flood peaks could be reduced by 29%
- But this is slow.
- Increasing infiltration rates; reducing surface runoff; increasing lag time
- Reduce Livestock
- Soil is less compact & +permeable; increased percolation
- But this reduces productivity.
- Soil is less compact & +permeable; increased percolation
- Contour Ploughing
- reduces soil erosion
- less efficient
- Aforestation
- River Restoration
- Returning the river to a more natural state
- Decreases efficiency
- Leaky dams
- Slow the flow of water w/o trapping
- Breaks easily
- Beaver Reintroduction
- Creates natural dams enables other species to create habitats eg. fish
- Increase channel stability, slows flow
- Flood risk
- The probability of a flood of a certain magnitude occurring affecting a number of people and their property.
- The higher the frequency the lower the magnitude.
- Hard Engineering
- CAUSES
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