Aldenham's flood risk is low, and the little there is comes from rain. No river or sea flood zone touches the village. No flooding is on record. A few postcodes show some sensitivity to heavy rain. Aldenham's water stays mostly where it belongs.
The Environment Agency's river-and-sea flood mapping puts none of Aldenham's postcodes in Flood Zone 3, the highest-probability band, and none in Flood Zone 2, the medium-probability band just outside it. Both figures are 0%. The village has no river large enough to put it in either zone. No house here is going to have a riverbank at the bottom of the garden.
Rain is a different matter. Surface water comes from heavy downpours that drains and fields can't absorb fast enough, and it is mapped separately from rivers and the sea. Here it is folded into the postcode measure below, alongside the other sources. Because the river-and-sea maps are clear, any risk in Aldenham comes from water running off the land, and that depends on how each street and driveway slopes. To check a particular house, put its full postcode into the Environment Agency's long-term flood risk service and look at the surface-water layer.
The forward look is just as clear. With the Environment Agency's allowance for climate change built in, the share of Aldenham's postcodes inside a river-and-sea flood zone is still 0%.
That should make insurance easy. A home outside every river-and-sea zone, with no flooding on record, is the kind insurers quote for without asking extra questions. The surface-water readings on a few postcodes are the only thing likely to make an insurer look twice. An early quote on the specific house will show whether it is one of those.
Counting every source together, about 4% of Aldenham's postcodes rate high on at least one flood measure, including surface water, none rate medium, and about 8% rate low. Each postcode is counted under the worst of several separate measures, so these shares cover more than the river-and-sea zones above and shouldn't be added to them. The overall pattern is a small pocket of rainwater risk in a dry village.
Defences don't come into it. The Environment Agency's modelled flood extents put 0% of Aldenham's postcodes in the high-probability area, with or without a defence in the model. Nothing needs holding back here, so there is nothing to ask about how sound a flood wall is. In places where the model does show a defence, that tells you a wall exists. It doesn't tell you the house behind it is safe.
The nearest tide gauge to Aldenham is at Portsmouth, where sea level rose by about 2 millimetres a year between 1962 and 2023. That is the rate measured at Portsmouth over those years, and it is about as relevant to Aldenham as Portsmouth is.
The Environment Agency's records show no historic flooding in the area. That is reassuring, but it means nothing has been recorded, which is not quite the same as nothing ever having happened.
Flood risk is one of Aldenham's real strengths. Rivers and the sea are not a threat here, and the only thing to check is surface water at the few postcodes that show it.