Flood management and SUDs

Flooding is certainly top of the agenda at the moment. While the climate scientists may debate whether global warming has been responsible for the recent extreme weather, it is clear that we can do nothing to control the weather instead we must look at what can be done to prevent flooding.

My training as an engineer has taught me to look at the root causes rather than just spending more money on flood defences. Two trends have been particularly detrimental to the management of flood water. The first has been the building of houses on flood plains. Flood plains exist for a reason – to hold flood water during extreme weather. If we persist in concreting them over, there is no where for the water to go. Tougher building controls are coming in but it very disappointing to see major plans to build on flood plains still being pushed forward.

The second trend is the move to tarmac over gardens and install more impermeable surfaces  - like the roofs of houses. Water falling onto a field can take several days to permeate into our rivers. When it falls on concrete it takes minutes. The result is very peaky flows that rise and fall dramatically. This is well recognised and the EA insists that for new building action is taken to limit the rate of water run off. Sustainable Urban Drainage (Suds) is now well accepted as a methodology for engineering ‘natural features’. 

The main constraint to the use of SUDs is deciding who takes responsibility for the long term operation and maintenance of the SUDs. This was first recognised years ago (Making Space for Water 2005) and is being addressed in schedule 3 of the water bill currently going through Parliament. This key schedule was due to be defined and enacted back in 2010, now 4 years later it is still not in place.

Lets hope the recent flooding is a wake up call and Sir Michael Pitts recommendations from the 2007 floods are actually acted upon.