Denmead's flood problem is the rain, not the river. About a third of postcodes carry high surface-water flood risk. About a quarter carry medium. The formal river-and-sea zones are far smaller. Surface water is what catches buyers who only looked at the river map.
On the river-and-sea side, the formal zones cover little ground. About one in twenty postcodes sits in Zone 3, the highest formal flood zone defined by the Environment Agency. Another small share, around two percent, falls into Zone 2, the next band down. Historic recorded fluvial flooding has affected well under one percent of postcodes. Denmead is inland, with no major river running through the village and the coast about six kilometres south. Rivers and the sea are not the central concern here.
On the surface-water side, the share rises sharply. Roughly a third of Denmead postcodes have at least some address at high surface-water flood risk. About a quarter have at least one at medium risk. Around four in ten have at least one at low risk. Surface water is the rain that does not soak away or drain off cleanly, and the formal river-and-sea maps do not capture it. Heavy rainfall overwhelming local drainage is the failure mode buyers need to understand. The distribution of the risk is not uniform across the village, which is why postcode-level data tells you something different from address-level data.
On the climate-adjusted view, the Environment Agency's projection covers more ground than the current formal zones combined. Close to nine percent of Denmead postcodes sit inside the climate-adjusted zone, the area the Environment Agency models as future flood-risk land under climate-change scenarios. The number is not yet a regulatory constraint, but it is what insurers and mortgage lenders are increasingly factoring into their pricing models. The current quote on a house is built on the current zones. The quote in ten years is more likely to be built on the climate-adjusted ones.
For insurance, the surface-water profile matters more than the river-zone share, because surface-water flooding is what most everyday claims look like. A property on a high-risk surface-water postcode can still get standard cover, but the underwriter will want the property-level risk picture before quoting. Premiums reflect what the underwriter finds, and the bigger the gap between the village average and the specific address, the more the quote will move. Conveyancing searches will flag any specific property in a formal flood zone, and that flag stays with the property file for the life of the building. The flood number on the spreadsheet today becomes the flood number on the mortgage application tomorrow.
On the published flood data, Denmead is among the higher-risk places in its district, and the rating across the dimension lands at one out of five. Anyone buying here without checking the surface-water map for the specific address is buying on hope rather than the data.