Mostly no, but the Thames decides the exceptions. Only a sliver of Ham is in the highest river zone. A wider fringe is in the band below it. No flooding is on record. Ham's flood risk mostly comes down to how close to the meadows you buy.
The Environment Agency's river-and-sea mapping puts about 1% of Ham's postcodes in flood zone 3, the highest-probability band, and about 15% in flood zone 2. The two bands are separate, so zone 2 is the medium-probability fringe beyond zone 3 and does not include it. Ham is mostly low river terrace, bounded on the west by the Ham Lands meadows and on the east by the rise towards Richmond Park, and the water knows which end is lower.
No separate surface-water figure exists for Ham alone. Surface water appears in the postcode indicators further down, mixed in with river and sea risk. The Latchmere Stream and the Sudbrook drain the higher ground along the foot of the hill, mostly underground, and surface briefly in Ham Common.
The Environment Agency also models the zones with an allowance for climate change, and on that version about 27% of Ham's postcodes fall inside. That figure comes from changing the model's assumptions about future rainfall and river levels, and it describes a possible future map, not the one buyers face today.
For insurance, the 1% in zone 3 is the slice an insurer looks at hardest. Homes in the zone 2 fringe usually get cover on ordinary terms but may be asked more questions. Two houses on the same street can be quoted differently if one is nearer the river meadows, so get a quote on the actual address early. Leaving it until the week of exchange is how people learn which house they bought.
A broader measure looks at every postcode and records its worst rating on at least one flood indicator, surface water included. On that basis about 8% of Ham's postcodes rate high on at least one measure, about 14% medium and about 50% low. These bands overlap with the zone figures above and use a different method, so the two sets should never be added together.
Counted in homes, the risk shrinks. The Environment Agency's rivers-and-sea mapping lists 2,155 properties in the Ham postcodes that carry any risk at all, and postcodes with none are left out entirely. Of those, 23 are at high risk, 15 of them homes, 11 at medium risk, 1,301 at low risk and 193 at very low risk. Most of Ham's exposure is low-level, and the high-risk list is short enough to count on a page.
The Environment Agency's flood extents put fewer than one postcode in a hundred in the high-risk area, and the share is the same whether or not defences are included in the model. A "defended" label on a particular house only means a defence appears in the model. It says nothing about how that defence would hold, and a buyer reassured by the word in a set of particulars has bought a word and nothing more.
The nearest tide gauge in this record is Portsmouth, which measured sea level rising by about 2 millimetres a year between 1962 and 2023. That is a rate measured on the south coast over those years. It is the only sea-level record available for Ham, and Ham is a long way inland of it.
No historic flooding is recorded for any part of Ham. That is reassuring, as far as records go, though records only show what someone wrote down. The gravel-pit lake at Thames Young Mariners connects to the river by a lock, and the river's level next to it is something the lock-keepers keep in mind.
Ham's flood risk is middling. Most of it is low and well mapped, with a small high-risk pocket close to the river and a climate model that widens the map.