The Government has placed priority on the need to take full account of the risks associated with flooding at all stages of the planning and development process, to reduce the future damage to property and risks to life and their expectations are enshrined within ‘PPS 25 – Development and Flood Risk’.
PPS25 identifies that flood plains are at risk from flooding but that water-corridor development are historically and currently popular areas for human habitats. Consequently, the risk of flooding for developments in these high risk areas needs to be assessed.
There is technical guidance on why and how to prepare a Flood Risk Assessment (EA R&D report FD2320 - http://www.hydres.co.uk/). It makes things look very difficult.
The hazards from flood water is the rate of flow and the final depth of water, and whether any flood defences will be adequate. A simple FRA, where there is little or no risk, is quick to produce. In high risk areas flood simulation programmes are required.