we really liked a house which had flooded in the past, twice, during very heavy rain storms, when there was massive water run-off.
There was a ditch running along the back of the house and garden, which then went under a small bridge through a narrow culvert. When there was a lot of rain, the narrow pipe in the culvert couldn't drain the ditch fast enough and the water backed up, and flooded the house.
The council rebuilt the bridge and the culvert and made a big wide mouth to the drain. The day the work was finished the house went on the market. Below market price, fabulous house with loads of space and a big corner plot garden. My dh is a water engineer. He sat down and worked out the drainage on the new ditch/ tunnel. He was not convinced that the job they had down would actually be enough to let the ditch drain during heavy rainfall, so I remain unconvinced by flood defences.
We phoned up our insurance company, we talked through the insurance with them and the cost etc. They were very reluctant, even given the new changes and the work signed off by the council etc etc.
In the end we walked away. the house sold, but since then we have had a lot of episodes of very heavy rain, unlike anything that used to be considered 'normal.' We talked about that house this week, and dh said, even if it has never flooded, every time it rained hard you would be worried, you would panic about flooding and sandbags etc. I am so glad we didn't buy it, the stress would have been really high.