Most of the area is not in a flood zone, and a small, specific slice of it very much is. The river and sea mapping puts only a sliver of postcodes in the highest zone. Add surface water and the picture widens. Four in ten postcodes sit within half a kilometre of the sea. This is not a question about Porthleven. It is a question about which street, and the gap between the two is where people get caught out.
On the Environment Agency's river-and-sea mapping, about 3% of the area's postcodes fall in flood zone 3, the highest-probability band, and under 1% fall in flood zone 2. Those two zones are separate bands rather than nested ones: zone 2 is the extra medium-probability fringe sitting beyond zone 3, which is why it can legitimately be the smaller of the two numbers. Anyone reading that as "zone 2 contains zone 3" has misread the map, and plenty of people do.
Surface water is not mapped as its own share here. It is folded into the combined postcode indicators further down, which matters because surface water is the flooding that arrives in places the river maps say are fine. What the record does carry is history: 12 flood events have been logged for this area, the most recent in December 2012, recorded as a main river event caused by a blocked bridge. Around 2% of postcodes fall within recorded historic flood extents.
Looking forward, the climate-adjusted zone raises the share to about 4% of postcodes. That is the allowance the mapping makes for a wetter, higher-sea future rather than a prediction of any particular winter.
For insurance, the practical point is that the address decides the premium, not the village. A property inside the mapped extent can face loaded premiums, a higher excess on flood claims, or an insurer routing the policy through the national flood reinsurance scheme. A property a few hundred metres up the hill will not. Get an indicative quote on the specific address before instructing a solicitor, because finding out at exchange is an expensive way to learn the postcode.
Taking all measures together, including surface water alongside rivers and sea, about 12% of the area's postcodes rate high on at least one indicator, about 11% medium and about 30% low. Those bands overlap with the zone figures above rather than adding to them, and they are shares of postcodes rather than of homes.
Counted as buildings, the Environment Agency's rivers-and-sea mapping lists 31 postcodes here carrying some level of risk, covering 620 properties. Of those, 57 sit at high risk, 21 at medium and 33 at low, with 13 of the high-risk properties being residential. Only postcodes carrying some risk appear in that list at all, so the totals describe the exposed edge of the area rather than the whole of it.
On whether anything stands between the water and the building, about 3% of postcodes sit inside a high-risk extent where a defence is present in the model, and about 2% inside a high-risk extent with no defence modelled at all. Present in the model is not the same as safe. It means the mapping assumes a structure exists, to a standard the mapping does not promise, maintained by a budget the mapping does not control.
The sea is close. About 41% of postcodes lie within 500 metres of the coast, the median distance across the area is roughly 790 metres, and the closest postcode sits about 13 metres from it. The 500 metre figure is a threshold the data draws, not a statement about any particular front door.
Every postcode here falls under a shoreline management plan, and the stated policy for this coast is to hold the line over the next 20 and 50 years, moving to no active intervention on the 100-year horizon. A policy is an intention to maintain defences over that period. It is not a guarantee, not funding, and not evidence that a defence already exists.
At the nearest tide gauge, at Devonport, the measured record from 1962 to 2015 shows sea level rising at about 2.3 millimetres a year. That is a historic rate from an instrument, not a forecast for this stretch of coast.
Flood risk here comes out middling, and deservedly so: most of the area is genuinely dry, a defined minority is genuinely exposed, and the century-scale policy for the coastline is honest about eventually stepping back. Buy on the specific address, never on the village average.