The soil in an alluvial plain is too good to be wasted. Floods were common but managable along the Medway until they built the Thames Barrier.

The area where I lived had been inhabited before the Romans came.

The reason they built the Thames Barrier was that the south east corner of England is sinking at a rate of about a tenth of an inch a year. They just didn't think about (or didn't care) where the water was going to go.