Coastal communities face greater threat of flooding due to land reclamation

Seafront communities are being left wide open to the risk of flooding because of the loss of coastal ecosystems, a Cambridge academic has warned.

Speaking at the Royal Geographical Annual Conference yesterday, Dr Tom Spencer said that the loss of saltmarshes, mangrove swamps, seagrasses and other natural buffers against wave energy, is leaving the world's coastal populations increasingly vulnerable.

Land reclamation along the shoreline has also increased tidal range and the risk of flooding in areas like the Thames estuary as waves to rush up deep channels restricted by sea walls and other defence structures. Dr Spencer, from the University's Department of Geography, believes that sea defences should be set back from the shoreline, allowing for the recreation of marshes and other natural areas of flood storage that will better buffer surrounding communities against storms and floodwaters.

The same policy would lead to the creation of biologically important habitats. But exactly how such a policy would be executed will require careful planning and further research.

"Our field studies in Essex show that under ordinary conditions very little wave energy reaches the base of a seawall fronted by 150m of saltmarsh," he said. "But if we are going to build new marshes how wide should they be? At what elevation should they be? And how should they be vegetated?

"If we can understand better how waves, tides, sediments and vegetation interact on natural marshes then perhaps we can come up with better guidelines for rehabilitation and reconstruction."

Dr Spencer's warning is particularly pertinent given concerns that a rise in sea levels, spurred by climate change, will increase water depths and, by extension, wave heights in stormy weather. If average global temperatures increase by 3.5 degrees C by 2080, the UK Met Office predicts that serious storm surges extending over 1.5m will occur once in every seven years on average. Under current conditions they are expected to occur once in every 120.