Flooding and Flood Prevention

 

Flooding is when a river gets more water than the river channel can hold. Therefore the river overflows.

There and human and physical causes of flooding.

Human Causes:

  1. Ploughing up and down slopes allows rain water to get to the river faster.
  2. Dams can burst meaning more(excess) water in river channels and flooding.
  3. If vegetation (plants etc.) has been removed, there is less interception and the water will move to the river faster
  4. Towns built on floodplain, storm drains will allow water to move into the river faster

Physical Causes:

  1. Impermeable rocks mean that rainwater cannot soak into the rocks. There water flows faster to the river on the surface or through the soil.
  2. A sudden rise in temperature can cause a thaw (melting). More water into the rivers
  3. Long Periods of hot weather can make the soil hard and dry, which means the water cannot soak in. More surface run-off
  4. River beds that have been silted up make the channel smaller and more likely to flood
  5. During a coldburst in a thunderstorm, the rain droplets are very large and fall quickly. There is no/little time for the water to soak into the ground and water runs very quickly into the river
  6. Large amounts of rain day after day mean the ground will become saturated and the water will flow more quickly into the river
  7. Steep Valley slopes make rainwater run off rapidly into the river

 

Infiltration – Infiltration is the process by which water on the ground surface enters the soil.

Surface Water – Water on the surface

Groundwater – Water in the ground

 

Prediction and Prevention

Prediction

  • Weather forecasts/news
  • Warning Codes (Flood watch/flood warning/severe flood warning/ all clear)
  • Likelihood of flooding in different areas
  • Websites
  • Organizations

 

Prevention of damage

  • Planning Permission (don’t build in flood prone areas – Flood risk assessment done)
  • Moving electrical sockets from low areas
  • Lightweight doors that can be moved (less damage to them if they’re moved)
  • Concrete floors instead of wood floors
  • Yacht Varnish to protect wood from water damage
  • Waterproof MDF (medium-density fibreboard) can be used instead of wood for door frames
  • Buildings on stilts (higher up/flood waters can pass under)
  • Waterproof plaster and wall covering
  • Chemical waterproofing

 

These will not be able to stop flooding, but, they will allow minimum/less damage to houses if they are effected by floods

Hard Engineering Techniques

This type of management involves major construction work

 

  • Embankments – These are raised banks along the river. They can be used as a path for pedestrians, can stop bank erosion and provide habitat for plants and animals. However, the banks are often not built high enough, are not nice to look at.

 

  • Channelisation – The river channel may be widened or deepened and this will allow it to carry more water. A channel can also be straightened so the water can travel faster. This protects the immediate area because water is moved away quickly and this is a long lasting technique. However, Altering the river can lead to greater risk of flooding downstream and this is an unnatural process.

 

  • Flood relief channels – The channel course of the river can be altered (changed) by diverting the floodwaters. This allows the people that live closer to the main river feel safer and this can be used for watersports. However, this requires a lot of land which can be expensive and difficult to purchase.

 

  • Dams – Dams can be built along the course of a river to control the amount of discharge and water is held back and released in a controlled way. But, This is an expensive process. Sediments can get trapped behind the dam, which can cause more erosion down stream. Settlements and agricultural land may be lost when the river valley is flooded to form the reservoir.
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