The lack of maintenance that would normally be expected is a fair point and something the authorities should be castigated for. That said some of the roads around Brighton and Hove are close to becoming undriveable due to potholes and lack for maintenance so the issue isn't unique to Somerset et al.
Have to agree with those saying if you don't want to be flooded then don't buy a house in an area liable to flooding. Those buying a property should always pay for a decent solicitor who will complete all the due diligence for getting this sort of information. From that point it is your choice (...