Click on the map below to see a bigger version. This map is taken from the 'Selsey Peninsula Strategy Review' which is a technical review prepared for the Environment Agency by a company called Babtie Brown & Root.

As you can see, the light blue line indicates where the potential flood risk is today (or from 2004) for a 1 in 1 year probability.

The dark blue line indicates where the projected 1 in 200 potential flood risk would be in about 50 years from now.

Of course, this would only occur if the current sea defences were not maintained!