Wooburn has a moderate flood risk, and most of it doesn't come from the river. No postcode is in the highest river zone. A small share is in the next band down. More than one in ten rate high once rainwater is counted. Add climate change and the map gets much bigger.
On the Environment Agency's river-and-sea flood zones, about 5% of Wooburn's postcodes are in zone 2, the medium-probability band, and none are in zone 3, the highest. Zone 2 covers the fringe beyond zone 3, so a village can have postcodes in zone 2 without having any in zone 3. The Environment Agency's records hold one flood event here, in December 1981, when a main river overflowed a channel that had no raised defences. Water is never far away in Wooburn, about 130 metres from the average front door, and on the official zones it mostly stays where it is.
Surface water is the risk the river zones miss. It comes from heavy rain that the drains and the ground can't take, and it can reach a house the river never would. With no postcode in zone 3, Wooburn's highest flood ratings come from those other measures, surface water among them. The best-looking postcode on the river map can still rate badly here.
Add climate change and the picture changes. The Environment Agency's climate-adjusted zones take in about 43% of Wooburn's postcodes. These zones are modelled from projected rainfall and river flows. A village that looks almost entirely dry on today's zones looks very different on the climate-adjusted map.
For insurance, a home outside zones 2 and 3 with no record of flooding usually gets standard cover without trouble. Insurers increasingly price surface-water and climate-adjusted risk as well. A house that rates high on any measure can therefore face higher premiums or a larger excess, even when it is nowhere near the river. The Environment Agency's long-term flood risk service shows each measure for a single address, and it is worth checking before asking for a quote.
Postcodes can also be rated on several flood measures at once, river, sea and surface water among them, with each postcode counted at the highest rating it gets on any one. On that basis, 14% of Wooburn's postcodes rate high on at least one measure, 19% medium and 57% low. In the modelled river flood extents, none of Wooburn's postcodes fall in the high-risk zone, either with defences or without them. A defence being present in the model would not make a house safe in any case. Here the question barely comes up, because the modelled river doesn't reach these postcodes at the high level at all.
The nearest tide gauge is at Portsmouth, where the sea rose by about 2 millimetres a year on average across its record from 1962 to 2023. That is a measured past rate on the south coast. Wooburn is an inland village in the Thames valley, so the sea is the one flood source it can largely ignore.
Wooburn's flood risk is middling. The river zones barely touch the village, while the surface-water ratings and the climate-adjusted map leave a good share of postcodes worth checking one address at a time.