Yes, and more than a town on a gentle slope has any right to be. The River Lea runs along one side of it. Cobbins Brook cuts right across the parish. About a quarter of the postcodes come up high on at least one flood measure. The forest end of town is on higher ground, and the risk gathers in the meadows by the river.
The Environment Agency's river-and-sea flood zones put about 10% of the town's postcodes in zone 3, the highest-probability band, and a further 12% in zone 2, the medium-probability fringe that lies beyond it. The two bands do not overlap, so they describe different stretches of ground. Most of that ground lies on the western side, where the land drops from the clay plateau in the east down to the marshes and meadows along the Lea, the river that also marks the county boundary with Hertfordshire. The Agency holds 107 recorded flood events for the area, the most recent in December 2000, when the main river ran over a channel with no raised defences. About 18% of postcodes fall inside the Agency's historic flood outlines.
Rain is the other half of the story. Surface water does not respect the zone maps, since it collects wherever the drains and the slope send it, and Cobbins Brook crossing the parish from east to west gives it a second route through town that has nothing to do with the Lea. The postcode measures below fold that in.
Looking further ahead, the Environment Agency's climate-adjusted flood zone covers about 29% of the town's postcodes. That is the outline the Agency draws once it allows for heavier rain and higher river flows, and it is wider than today's zones by a margin a buyer planning a long stay should notice.
Insurance follows the map. A home inside the river zones, or one with a recorded flood in its past, can expect more questions from insurers, higher premiums or a larger excess, while homes on the higher eastern ground towards the forest are usually an easier conversation. The most useful step is to get a buildings insurance quote on the exact address early, since an insurer's price is the market's own reading of the risk.
At postcode level the picture widens. About 26% of Waltham Abbey's postcodes rate high on at least one of several flood measures, surface water among them, about 31% rate medium on at least one and about 53% rate low on at least one. A single postcode can appear in more than one of those groups, because each measure is scored separately.
Counting homes changes the feel of it. The Environment Agency's rivers-and-sea mapping lists 2,904 properties in the town's at-risk postcodes, and only postcodes carrying some risk appear in that list at all. Of those, 36 properties are at high risk, 28 of them homes, 114 are at medium risk, 557 at low risk and 1,088 at very low risk. Thirty-six is a small number in a town this size, and each of the 36 is a whole household's problem.
Defences barely change the picture. About 9% of postcodes sit in the high-probability extent with no defence in the model, against about 1% where a defence is present, and "present" only means the model includes one. It says nothing about whether that defence holds on a given night. The flood of December 2000 came from a channel with no raised defences, and the mapping suggests that is still the usual arrangement along most of the Lea's edge here.
Flood risk is one of Waltham Abbey's weaker points, concentrated on the river side of town and serious enough there that the exact street decides how much of it you buy.