1 September 2006Ian Sample
Low-lying stretches of the seafront act as natural buffers to encroaching seas, but defences built to protect the land forces water to go elsewhere, making it more likely that storm surges will trigger dramatic flooding by inundating estuaries and neighbouring coastal areas.
In Britain, the problem is most acute in regions such as Essex and Norfolk where saltmarshes and other intertidal zones are protected by walled defences. While the barriers protect land locally, they force water inland elsewhere, increasing the tidal range and risk of flooding along the Thames estuary.
Speaking at the Royal Geographical Society meeting in London yesterday, Tom Spencer, director of Cambridge University's coastal research unit, called for the creation of new coastal wetlands by setting sea defences further back from shore.
The controversial proposal could see residents and landowners compensated for reducing the flood risk to neighbouring communities.
"We should be looking to recreate marshes in front of defence structures, and we should be looking to re-engineer estuaries and open coast to include coastal ecosystems which can dissipate wave energy," said Dr Spencer.
"Most of our flood defences were strengthened, repaired and raised after the massive storm surge of 1953 and 50 years on, most of those are approaching the end of their life, so now is an important time to be thinking about this. Do we just replace them, or look at these other options? We need to have that debate."
Field studies in Norfolk and Essex revealed how waves quickly lost power as the water surged inland. By recreating the similar marshlands elsewhere, the risk of serious flooding could be reduced substantially, the researchers believe.
In Britain, coastal building has seen a dramatic reduction of intertidal land, with around 40% lost along the Thames estuary. The problem of flooding is becoming more acute around the world as populations move to the coast.
According to Dr Spencer, climate change makes the need for newly-created wetlands even more urgent.
Calculations from the Met Office show that a 3.5C temperature rise by 2080 would see serious storm surges topping 1.5m strike the east coast of Britain once every seven years, instead of once every 120 years, as experienced today.
