Mostly no, but the drains are the asterisk. Zero postcodes sit in current river or sea flood zones. Nothing in the village has flooded in the historic record. About one in eleven postcodes carries some high surface-water risk though, and another one in seven carries medium. The sea is not the problem. The drains can be.
On the official river-and-sea flood maps, Southbourne is genuinely clean. Zero percent of the area falls into either of the two zones that signal real flood-plain status. The historic flooding record is also zero. The village sits high enough relative to Chichester Harbour and far enough back from any meaningful river that the standard river-and-sea threat picture does not apply here. That is not nothing for a postcode this close to a wetland of international importance.
Surface water is the actual flood story. Roughly one in eleven postcodes carries some high surface-water flood risk, about one in seven carries medium risk, and close to four in ten carries some low risk. This is the kind of flooding that happens when an hour of heavy rain has nowhere to go because the drainage cannot keep up. It is more common in places with hardstanding and impermeable surfaces than buyers expect, and post-war village expansion is exactly the kind of building pattern that produces it. The high-risk postcodes are not evenly distributed across the village, so checking the surface-water flood map for the specific address matters more than reading the headline.
Climate-adjusted projections push the picture further. About two percent of the area falls into a flood zone once sea-level rise and increased rainfall are modelled in. That is small but non-zero, and it concentrates in the postcodes closest to the harbour. About one in seventeen postcodes sits within five hundred metres of the coast, and the median postcode is roughly a kilometre back. The nearest long-running tide gauge at Portsmouth has been recording a sea-level rise of about two millimetres a year since the 1960s. The shoreline management policy for this stretch is hold-the-line across twenty, fifty and one-hundred year horizons, which is reassuring within its own terms but does not promise the maths will stay favourable forever.
For insurance, the practical implication is straightforward. The river-and-sea map being clean means most addresses will not trigger the specialist-cover regime that high flood zones impose. The surface-water risk is more nuanced. Insurers price on postcode-level surface-water data too, and addresses in the higher-risk zones can carry meaningful premium loadings without anything dramatic on the river map. Get quotes before exchange, not after.
Average flood risk for an English village next to a protected harbour, which is exactly what the numbers add up to. Nothing catastrophic on the official maps. Surface water is the risk to read. Climate is the risk to watch.