Parts of Banwell flood, and parts do not. About one in seven addresses sit in the highest river-flood zone. Almost none fall in the middling zone in between. The village lies on the edge of the drained Somerset Levels, where a fifth of postcodes fall under a drainage board whose whole job is keeping the ditches moving. The risk is real, concentrated in one corner, and simple to check before you commit.
The river and tidal picture is where the numbers gather. Around one in seven addresses land inside the highest flood zone, the band carrying the greatest chance of river or coastal flooding. Barely any sit in the lower-probability zone below it. That is an unusual shape. Most places grade gently from dry to wet, whereas Banwell jumps almost straight from safe to high, which is the tell of low ground kept dry by drainage rather than a floodplain that eases in slowly.
Add surface water and local drainage and the reach widens a little. About a third of postcodes carry at least a low risk of the flooding that comes when heavy rain overwhelms the drains and ditches rather than a river bursting its banks, and roughly one in seven sit at the high end of that scale. On the Levels the two problems are cousins, because the same flat, slow-draining ground that struggles to clear a downpour is the ground the rivers back up onto.
The forward look is the part that steadies the nerves. Under the standard climate allowance, which loads expected sea-level rise and heavier rainfall onto the maps, no extra Banwell land tips into the top zone. There is also no recorded history of past flooding across the village. The exposure that exists is the exposure already on the map, not a share quietly climbing the streets year on year.
For insurance, the split matters far more than the headline. A home clear of the flood zones will insure like any other house in the country. A home inside the top zone can mean a higher premium, a bigger excess, or a policy that needs the flood cover written in on purpose rather than assumed. None of that stops a sale, but it is a question to put to the seller and the insurer at address level and not street level, because two houses on the same road can sit on opposite sides of the line.
Flooding in Banwell is a middling, manageable risk: a genuine problem for about one in seven homes and a non-event for the rest. Get the specific address checked, and let that answer pick the house rather than the postcode.