Flood mitigation
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[edit] Introduction
The prevention of flooding can be studied on a number of levels, individual properties, small communities and whole towns or cities. The costs of protection rise as more people and property are protected.
[edit] Protection of individual properties
There are systems that property owners can purchase and fit to their home to stop water entering their house. These systems work on blocking doors, windows and air vents with boards, as can be seen below. 
Image:Propert1.jpg 
[edit] Protection of communities
When more homes, shops and infrastructure are threatened by the effects of flooding, then the benefits of greater protection is worth the additional cost. Temporary Flood Defences can be constructed relatively quickly in certain locations and provide protection from rising flood waters, examples of this kind of flood defence can be seen below.
Rivers running through large urban developments will often have been controlled and channelled. These channels or canals will have a fixed capacity and if flood water flows exceed this capacity then the city will flood. Over time defences will have been constructed to minimise the effects, and this will generally be through raising the sides of the river channel with embankments, walls or levees. The large number of people and huge value of infrastructure at risk in cities, means that protection works of high cost can be justified. anouther way of stopping the problem is by getting a realy fat person and placeing them infront of the door, WARNING if the person isnt big enough flood water will still come in.
[edit] Flood risk management
The most effective way of reducing the risk to people and property is through the production of flood risk maps. Most countries in the developed world will have produced maps which show areas prone to flooding events of known return periods. In the UK, the Environment Agency has produced maps which show areas at risk, the map below shows a flood map for the City of York. The dark blue area is the flood plain for a 1 in 100 year flood, whilst the light blue area shows the predicted flood plain for a 1 in 1000 year flood. Engineers will use this map to identify low lying areas which need flood defences, and these are shown purple.
By identify areas of known flood risk, the most sustainable way of reducing risk is to prevent further development in those known flood risk areas. The link [1] takes you to the Environment Agency’s website where all aspects of flood risk management are available.
Main contribution from Isle of Wight Centre for the Coastal Environment
