Hertford Heath is safe from rivers and the sea, and less safe from rain. None of the village falls in a river or sea flood zone. The climate-adjusted map adds nothing. About one postcode in seven still rates high on at least one flood measure. The danger here comes from above, the river being a long way below.
The Environment Agency's river-and-sea flood zones cover none of Hertford Heath's postcodes: 0% in Flood Zone 3, the highest-probability band, and 0% in Flood Zone 2, the medium-probability fringe beyond it. The village is on a heath above the Lea valley. The Lea floods the valley floor, and the village was built where the valley ends.
Surface water is a different matter. A flood zone only describes rivers and the sea, and rain that falls on a hilltop and has nowhere to drain does not show up on that map at all. On the measures that fold surface water in, some of Hertford Heath scores high even though no river can reach it. A home can be outside every flood zone and still have water at the back door after a cloudburst, if it is at the bottom of a slope or next to a blocked drain.
The Environment Agency's climate-change allowance, which redraws the river-and-sea zones for higher future flows, puts 0% of the village's postcodes inside them. Higher ground is the one flood defence that needs no maintenance budget.
For insurance, that mix usually helps. Insurers price river and sea risk heavily, and none applies here, so most homes in the village should be ordinary to cover. A house that sits on one of the surface-water flow routes can still be quoted differently from the house across the road, and the quote is where you find out which one you are buying.
The postcode-level picture, which counts a postcode if it rates on any of several flood measures including surface water, puts about 14% of Hertford Heath's postcodes at high risk on at least one, about 14% at medium risk on at least one, and about 37% at low risk on at least one. With the river-and-sea zones empty, the higher ratings come from the other measures. "Not in a flood zone" will be true of every house you view here, and on about one postcode in seven it is the less useful half of the answer. Look the exact address up on the Environment Agency's surface-water flood map. That map shows where rain runs and pools street by street, which a village-wide figure cannot.
The Environment Agency's modelled flood extents put 0% of postcodes in the high-risk extent, whether or not a defence is present in the model, and 0% in the low-risk undefended extent. There is nothing to report on defences because, on the river model, nothing here needs defending. That says nothing about surface water, which no wall or embankment is built to stop.
Hertford Heath has no recorded history of flooding: 0% of the area falls within the Environment Agency's records of past flood outlines. That is reassuring, and it means only that nothing was mapped. A flooded garage on a wet night rarely makes the official record.
The flood risk in Hertford Heath is middling: the river can be crossed off the list, and the rain cannot, and the rain is the part that varies from one house to the next.