Great Leighs has almost no river or sea flood risk, and what risk it has comes from rainwater with nowhere to go. No postcode in the village is in a river or sea flood zone. Allowing for climate change does not move that. About one postcode in nine still carries a high flag on some measure. So the risk is local and patchy, and it depends on which street you buy on.
On the Environment Agency's river-and-sea mapping, 0% of Great Leighs' postcodes are in Flood Zone 3, the highest-probability band, and 0% are in Flood Zone 2, the medium-probability band outside it. That is the measure most sale particulars refer to, and in Great Leighs it is clear.
Surface water is a separate risk, the kind that comes from heavy rain overwhelming the ground and the drains before any river is involved. The river zones are empty, so any flood flags on Great Leighs postcodes come from the other measures, and surface water is the main one of those. That risk depends on the dip in a road, the slope of a garden and where the nearest drain is, and it varies from one close to the next.
Looking ahead, the Environment Agency's zones adjusted for climate change also cover 0% of the village's postcodes. On the river-and-sea measure, the extra rainfall and higher river levels built into that projection still leave Great Leighs out of the zone.
For insurance, a clean river-and-sea picture is the part most underwriters look at first, and it helps. A surface-water flag can still appear in an insurer's own model and push up a quote for one house while its neighbour gets the standard rate. Putting the exact address into the Environment Agency's long-term flood risk check, and getting a buildings insurance quote while the solicitor is still on searches, will show which kind of house it is.
The postcode-level picture combines the measures. Counting any of several flood measures together, rivers, sea and surface water among them, about 11% of Great Leighs' postcodes rate high on at least one, about 13% medium and about 44% low. Because a single postcode only needs one flag to count, these shares sit on top of the clean river zones without contradicting them. Most of the village is flagged low or not at all; a minority of streets account for all of the high flags.
The defences question hardly applies. In the Environment Agency's modelled high-probability flood extents, 0% of postcodes are undefended and 0% are defended. In plain terms, the model places nothing in the main river flood area, so there is no defence for a homeowner to rely on and nothing that needs one.
No historic flooding is on record for the area, with 0% of it inside the Environment Agency's recorded flood outlines. That is worth something, since recorded floods tend to recur in the same places. Surface-water floods are recorded far less thoroughly than river floods, though, and a drive that floods once in a cloudburst rarely makes it into the national record.
Great Leighs is in the middle on flood risk. The rivers leave it alone, and the remaining risk depends on the individual property, so each address needs checking.