Writtle's flood risk comes from rain, and the river is barely a factor. None of its postcodes fall in the river-and-sea flood zones. Only a handful of homes register any river risk at all. Fewer than one postcode in ten rates high on some measure once surface water is counted. The village's real flood question is about rain running off, and the river hardly comes into it.
On the Environment Agency's flood zone mapping, 0% of Writtle's postcodes are in flood zone 3, the highest-probability band for flooding from rivers and the sea, and 0% are in flood zone 2, the medium-probability fringe that lies beyond it. For river and sea flooding, that is as clean a result as the map can show. The Romans valued Writtle partly for how easily the river could be forded, which makes it the oldest flood survey the village has.
Those zones only measure water coming out of rivers and the sea. Surface water is a separate problem, rain falling faster than the ground and drains can take it and then running down roads and pooling in dips, and it appears nowhere in the flood zones. In Writtle that is the risk worth looking at, and it shows up in the postcode-level measure below.
Looking ahead, about 2% of Writtle's postcodes fall inside the Environment Agency's flood zone with an allowance for climate change, the version of the map that adds the extra rainfall and river flow expected in future. It is a small share, and it marks the few spots where the river's edge could move closer to houses.
For insurance, being outside both river-and-sea zones helps, because that is the first question many insurers' systems ask. Surface-water flags are applied postcode by postcode and can still turn up in a quote, so the household on a flagged postcode may pay more than a neighbour two streets away, and the village's clean river map will not help them argue the point.
The broader postcode measure counts a postcode if it rates at a given level on at least one of several flood measures, surface water included alongside rivers and sea. On that basis, about 9% of Writtle's postcodes rate high on at least one measure, about 18% medium and about 32% low. That is where the village's flood risk shows up, and it varies from one street to the next. The Environment Agency's long-term flood risk service lets anyone look up a single address and see the surface-water result on its own, and that result matters more than the village-wide numbers.
Counting homes gives a smaller picture. The Environment Agency's rivers-and-sea assessment lists only the postcodes that carry some risk, and in Writtle that is five postcodes containing 572 properties. Of those, three properties are rated high risk, two of them homes, four are medium and ten are low. The rest of the village does not appear on that list at all.
On the question of defences, the Environment Agency's modelled high-risk extents cover 0% of Writtle's postcodes with a defence in place and 0% without one. Nothing in the village falls in the modelled high-risk area, so the question of whether a defence stands in the way never comes up. Where a defence does appear in that modelling, it only means a structure exists, and it says nothing about whether a house behind it stays dry.
Writtle's flood risk is moderate overall. The river is close to a non-issue, and the rain decides which streets need a closer look.