Mostly no, but the riverside risk is real. Only a small sliver of the town sits in the river-and-sea flood zones. About one postcode in eleven rates high-risk on at least one measure. There's no recorded history of flooding in the area. The risk sits on the low ground by the Medway and in the valley, and the hillside streets are largely clear of it.
On the Environment Agency's river-and-sea mapping, about 2% of Chatham's postcodes fall in flood zone 3, the highest-probability band. Another 1% sit in flood zone 2, the medium-probability fringe beyond it. The two bands don't overlap. Zone 2 covers only the extra ground past zone 3, so it can be the smaller number without contradicting anything. For most of the town, the River Medway is scenery, not a threat.
Surface water is a separate question, and there's no standalone figure for it here. It's included in the postcode indicators further down. The town centre lies at river level, and the High Street runs along The Brook valley, so rain that falls on the slopes around it has to go somewhere. Buyers on the valley floor should check the surface-water map for their exact address, not rely on the river zones.
Looking ahead, the Environment Agency's climate-adjusted mapping puts a little under 5% of postcodes in the flood zone once future conditions are factored in. That's a bigger footprint than today's, and it still leaves most of the town outside it.
For insurance, the few properties in the higher zones should expect underwriters to ask more questions and possibly quote higher premiums. Most homes on the slopes should see flood risk play little part in the price of cover. The only reliable test is a quote for the exact address before you commit.
At postcode level, about 9% of Chatham's postcodes rate high-risk on at least one flood measure, about 15% medium and about 32% low. These bands fold surface water in with rivers and the sea, and a postcode only needs one measure to qualify. They overlap with the zone figures above and shouldn't be added to them.
In homes rather than postcodes, the Environment Agency's rivers-and-sea mapping lists 1,107 properties with some level of risk, across the 51 postcodes that carry any at all. Of those, 97 are at high risk, 211 medium, 402 low and 72 very low. Only 20 of the high-risk properties are homes. Postcodes with no river or sea risk don't appear in this count.
On whether anything stands between the water and the houses: about 2% of postcodes sit inside the high-probability flood extent with defences ignored, and about 1% with defences included. "Defended" means a defence appears in the model. It doesn't mean the property is safe, and a defence can be overtopped or fail.
The water is close in places. The nearest postcode is about 25 metres from the coast, and about 9% of postcodes are within 500 metres of it. That 500-metre line is a threshold the mapping uses, not a verdict on any single address. The median postcode is about 2.8 kilometres from the coast, so for a typical home the tidal Medway is a view, not a neighbour.
The shoreline management plan for this stretch sets a policy of holding the line at 20, 50 and 100 years. That's a stated intention to maintain the existing defences over those periods. It isn't a funding guarantee, and it doesn't create any defence that isn't already there.
The nearest long-running tide gauge, at Dover, recorded sea level rising by about 2 millimetres a year between 1961 and 2010. That's a measured historic rate over that record, not a forecast.
There's no recorded flooding in the area. That's reassuring, though an empty record doesn't prove water has never come up; it means none has been logged.
Flood risk in Chatham is middling and concentrated. A few low-lying streets carry most of it, and a buyer who checks the exact address will know which side of that line they're on.