We all know by now that we should not be building on flood plains. It exposes buildings to very increased flood risk and reduces the area of the flood plain, reducing its ability to absorb flood water and increasing the risk of floods elsewhere.

Our legacy of flood defences, however, may be causing just the same problems. Our Sussex rivers are canalised - restricted between substantial flood defences. The reason for this was agricultural production.

Decades ago we drained flood plains and built flood defences in order to produce productive arable land rather than grazing marshes. At the same time the wildlife associated with grazing marshes declined.

The idea was that floodwaters collecting in these rivers would be encouraged to rush downstream and out to sea, keeping the land dry and productive.

In practice, flood waters go downstream until they meet some resistance, such as a bridge in the middle of a town, or some weak link or low point in the defence. Then they start to flood.

Instead of the flood plain acting as a flood plain, previous flood defence practice restricted the waters into limited space until they build up and eventually flooded.

Once rivers do burst through flood defences the floodwaters are unable to get back into the river even if levels go down, resulting in an unpredictable spread of the water.

There have been predictable calls for significantly more funding to be put into defending land from floods. But our rivers have become de-naturalised. Natural, functioning flood plains have become treated as pipes through which water is forced to flow.

Throwing more heavy engineering at the problem will not make it go away. Flood defence resources should be put into re-naturalising our flood plains.

The strongest flood defences should be built around buildings and urban areas, with significantly reduced defences along the rest of the flood plain, allowing flood waters to be absorbed rather than forced into the weakest link.

-Dr Whitbread, Head of Conservation, Sussex Wildlife Trust