Parts of it, yes, and you can guess which parts. The town was built where two rivers meet and empty into a harbour, which is exactly the arrangement that makes a place lovely to look at and complicated to insure. Most postcodes carry no meaningful risk at all. A minority carry a great deal. The flood question here is not whether the town floods, it is whether the specific house does, and those are very different questions with very different answers.
On the Environment Agency's river-and-sea mapping, around 9% of the area's postcodes fall inside flood zone 2 and about 5% inside flood zone 3. Those two bands are exclusive rather than nested. Zone 3 is the higher-probability core, and zone 2 is the additional medium-probability fringe sitting outside it, which is why the outer band can be the larger number without any contradiction. Anyone reading a flood map for the first time gets this backwards, and estate agents rarely rush to correct them.
Surface water is folded in with rivers and sea in the postcode-level indicators used here, so there is no separate surface-water-only share to give. What the recorded register does carry is history: 10 recorded flood events in the area, the most recent in February 2014. That is a real count of things that happened, not a model of things that might.
Looking forward, the Environment Agency's climate-adjusted mapping puts around 15% of the area inside a flood zone once allowance is made for future conditions. That is a meaningful step up from the present-day zone shares, and it is the figure a buyer holding a property for twenty years should be reading rather than the current one.
For insurance, this matters more than most buyers expect. A property inside a mapped zone can face higher premiums, higher excesses, or a requirement to disclose previous claims, and the difference between two houses on the same street can be substantial if one sits inside a boundary and the other does not. Get an indicative quote before instructing a solicitor rather than after, because the quote is the only thing that tells you what the mapping actually costs you.
Taking every indicator together, including surface water alongside rivers and sea, about 9% of postcodes rate high on at least one measure, around 10% rate medium, and roughly 36% rate low. Those bands overlap with the flood-zone figures rather than sitting alongside them, so they cannot be added together. They describe the same water from a different angle.
Counted as homes rather than postcodes, the Environment Agency's rivers-and-sea mapping lists 6,820 properties across the 281 postcodes that carry any risk at all. Of those, 335 sit at high risk, 180 at medium and 3,029 at low. Around 251 of the high-risk properties are residential. Postcodes with no risk do not appear in that listing at all, which is worth remembering before the total starts looking like the whole town.
On whether anything stands between the water and the building, the modelled extents split roughly evenly. About 6% of postcodes sit inside a high-probability extent with no defence present in the model, and around 4% sit inside one where a defence is present. That second figure is not reassurance. It means the model knows a defence exists, not that the defence will hold, not that it protects your particular address, and not that it is maintained to the standard you would assume.
The coast is close. Around 25% of postcodes sit within 500 metres of it, which is a threshold the data defines rather than a claim about any single address. The nearest postcode to the water sits about 13 metres from it, and the median across the area is roughly 950 metres.
Every postcode here falls under a shoreline management plan, and the stated policy at the twenty, fifty and hundred-year horizons is hold the line, meaning the intention is to maintain defences where they exist. A policy is an intention held by public bodies with finite budgets across a century. It is not a guarantee, and it is not the same thing as a defence already standing in front of your house.
At the nearest tide gauge with a long record, at Portsmouth, sea level rose at about 2 millimetres a year across the 1962 to 2023 record. That is a measured historic rate over sixty years, not a projection of what comes next.
Flood risk here lands somewhere in the middle, which is the least satisfying answer and the honest one. The town as a whole is not a flood town, but a meaningful slice of it is, and the difference between buying the safe version and the exposed one comes down to a boundary line you cannot see from the pavement.