Long Ashton is mostly dry, and the risk it carries comes out of the sky rather than up from a river. Fewer than one home in a hundred sits in a mapped river or coastal flood zone. Surface water is a different matter, touching close to one postcode in ten at the high end. The threat here is heavy rain finding the low ground, not a swollen river breaching its banks. On the whole this is a low-lying-worries kind of place, with one caveat worth a survey.
Take the rivers and the sea first, because that is where the reassurance sits. Only about one postcode in a hundred falls into the medium river or coastal flood band, and a similar share sits in the highest-probability zone. For an inland village on the edge of Bristol, that is close to the floor of what any English settlement carries. If your worry is the classic image of water rising through the front door from a nearby watercourse, the maps do not support it for most of Long Ashton.
Surface water is the part that earns attention. Around nine in a hundred postcodes carry a high surface-water flood risk, roughly seven in a hundred a medium risk, and a further share a low one, so once you add them up something like a fifth of the village has at least some exposure to water pooling and running off during heavy downpours. This is the flooding that arrives when a summer storm dumps more rain than the drains can move, and it does not respect the tidy boundaries of a river zone. It is patchy and street-specific, which means the village average tells you far less than the individual property does.
Looking forward changes the numbers only slightly. Once the standard climate allowance is applied to account for wetter future conditions, the share of the village in the higher river flood band rises to about one postcode in a hundred. That is a small uplift on today's position rather than a step change, so the direction of travel is gently worse, not alarming. The homes at risk in fifty years are broadly the homes at risk now.
For insurance, the split matters more than the headline. The large majority of Long Ashton homes should attract standard buildings cover without a flood loading, because they sit clear of every mapped zone. The minority exposed to surface water are where premiums can climb and where an insurer may ask for a flood survey or a history of past claims before quoting. The only way to know which side of that line a given house sits on is to check the specific address, not the village, because two homes on the same road can carry very different answers.
The verdict is a genuine middle. Long Ashton is not a flood plain and most of it is comfortably dry, but the surface-water exposure across a meaningful slice of postcodes stops it being a clean bill. Treat it as average risk that hinges entirely on the exact property, and get the individual flood report before you commit.