Confusion over data used to offer flood insurance in mixed flood zones.
CFELH
Forumite 
I am told the insurers use ‘Gov data’ to determine flood risk for offering flood insurance. So, in the example below, can anyone who perhaps works in insurance explain how insurers derive information from two conflicting sources run by the same Gov agency?
My son is buying a home in a street of eighteen houses. The street is surrounded by a flood plain which flooded quite badly in 2019. The ‘Gov long term flood risk website’ confirms all properties in this street are ‘very low risk’ for rivers, sea and surface water. So far, he has had no trouble obtaining insurance quotes for flood.
However: many the homes that surround this street for up to 1km radius are in flood zone three when viewing the ‘Flood map for planning’. But low risk when consulting the ‘Gov long term flood risk website’ despite 50 homes in this area being flooding in 2019.
How can 50 homes that flooded in 2019 be categorised by planning to be in flood zone 3, but the same properties be deemed low risk for long term flooding, and insurance purposes?
Replies
Long term view is saying what the flood risk is assuming nothing else changes and so at the moment it doesn't sound to be too bad for where they are. The planning view however considers what will happen if more land is covered by concrete and other non-permeable materials so surface water cannot be absorbed. As such its possible to be in an area that is ok for now but would become problematic if it became more built up.
For those that aren't buying reinsurance from Flood Re then there is the government data, several third party models like RMS, Air etc plus some large insurers may be able to come to their own view... one prior client used RMS with a loading factor for non-Flood Re cases as they found RMS was always a little too pessimistic on the likely losses.