dennis@home wrote:

What people forget is that flood plains are natures way of controlling
floods and if you build on them you will get flooded. What's needed is
some sanity and to stop building where you shouldn't and pull the houses
down that do flood frequently rather than *moving* the floods to
somewhere else by building flood defences.

You can't do that. Planning departments are infamous for lack of common
sense. A relative was plagued by a damp patch on his dining room wall.
In desperation, he lifted the floor boards and found that he was looking
at his reflection in the water under the floor. By chance, I talked to
someone who lived in the area and he said that he wondered what would
happen when they built that group of houses on the local duck pond!
Relative moved quickly.