Harrietsham's flood risk is low from the river and middling once rain is counted. Almost no postcodes sit in the river-and-sea flood zones. A small minority carry high risk on at least one measure. There is no recorded flooding on file. Ask about the rain before you ask about the river.
On the Environment Agency's river-and-sea flood zones, about 1% of the area's postcodes fall in zone 2 and none fall in zone 3. The two are separate bands: zone 3 is the higher-probability core, and zone 2 is the medium-probability fringe beyond it. The River Len runs through the village south of the M20, and on this measure it keeps to itself.
Surface water is where the risk lives. It has no separate figure of its own here, but it sits inside the postcode indicators set out below, and those run higher than the river zones do. Rainfall that the ground and drains cannot absorb fast enough is the flood most likely to find a Harrietsham address.
Looking forward, the Environment Agency's climate-adjusted flood zone takes in about 1% of postcodes. That is a modelled future, not a current map, and on this measure the change is small.
For insurance, a home outside the river-and-sea zones is usually the easier conversation. The postcodes flagged for surface water are where a quote can come back higher or with conditions attached, so get an indicative quote on the exact address before paying for a survey.
At postcode level, 6% of the area's postcodes rate high risk on at least one flood measure, about 8% rate medium and about 17% rate low. These measures fold surface water in alongside rivers and the sea, so they overlap with the zone figures above and cannot be added to them. A postcode rated high on one measure can sit comfortably outside every river zone.
Counting homes rather than postcodes is sharper. The Environment Agency's rivers-and-sea risk mapping lists ten postcodes in the area carrying any risk at all, holding 247 properties. Of those, six properties are at high risk, four of them homes, nine are at medium risk and 20 at low. Postcodes with no river or sea risk do not appear on that list at all, which is why the total is small.
On defences, none of the area's postcodes sit inside the high-probability modelled flood extent, whether a defence is present or not, and about 1% sit inside the low-probability undefended extent. A defence showing up in a model only means something stands in the way on paper. It is not a promise the water stays out.
The coast is at least 6 kilometres away and typically about 9, but about 27% of postcodes still fall under a shoreline management plan. The policy for the stretch that covers most of them is to hold the line over 20, 50 and 100 years, meaning the stated intention is to keep maintaining the existing defences. A stated intention is a plan, not a wall, and plans get revised.
The nearest tide gauge, at Dover, recorded sea level rising by about 2 millimetres a year across its 1961 to 2010 record. That is a measured historic rate, not a forecast, and at this distance from the sea it is background rather than a threat to the village.
The area has no recorded historic flooding on the Environment Agency's records. That is reassuring. It is also a statement about what was recorded, not a guarantee that no garden, cellar or lane has ever taken water.
Harrietsham sits in the middle on flood risk: the river leaves it largely alone, and the surface-water flags keep it from being a clean bill of health. Check the individual address, because in a place like this the street matters more than the village.