The extensive shore line of Portsmouth, Langstone and Chichester harbours is highly vulnerable to flooding from climate induced rises in sea level, that requires construction of new coastal defences.

Using a variety of tried and tested responsive modern tidal barrages across the entrances of Chichester, Langstone harbours and Portsea island creek might more rationally reduce flood vulnerability than the extensive length of coastal defences currently envisaged.

The approach identified here also protects existing populations, amenity and recreational facilities, and preserve habitats more effectively and efficiently.