Best use of floodplains : ...

Best use of floodplains : Traditionally floodplains have been used for agricultural and urban development because they are flat and (in the case of urban development) near rivers for transport, etc.  Banks and walls have been built to prevent flooding.  However this causes higher flood levels in rivers because the flow area is reduced.  The best use of floodplains is to allow the areas to flood and only use the land for purposes that are resilient to flooding (for example, pasture where animals can be removed from the floodplain in flood periods).  This approach means that flood levels are lowered and downstream flood flows are reduced.  Bearing in mind that many existing floodplains have defences, the use of floodplains could be improved by the construction of ‘polders’ that store flood water and reduce downstream flooding.  However this is a very artificial situation.  Another possibility is to breach or remove the defences, allow flooding on the floodplains and allow the rivers to develop naturally.  This is only possible where the impacts of flooding on existing floodplain development are accepted (e.g. loss of agricultural land, flooding of properties, etc.).

 

Defined public policy for economic use of flood plains : There are countries that have floodplain policies related to the use and development of floodplains, including the UK.  However they have to deal with an existing situation where development on floodplains already exists.  The policies are therefore often concerned at avoiding new development in flood risk areas, and measures to reduce risk to existing development.

 

Free software available to mark river flood plains : HR Wallingford does not use free software for this purpose but I think the HEC-RAS modelling system from the USA is free.