Reservoir flood risk
A residual, very-low-probability ‘what-if’ risk — the consequence if a large reservoir were ever to fail. Reservoirs in England are closely regulated and regularly inspected.
Reservoir flooding is different from every other source in this report. It is not an everyday likelihood but a residual consequence: the area that could be reached if a large reservoir were ever to fail and release its water. Large raised reservoirs in England are governed by the Reservoirs Act 1975, closely regulated and regularly inspected by qualified engineers, which is why an actual failure is extremely rare.
The Environment Agency maps the maximum area that could be flooded if a reservoir failed, usually in two scenarios — a “dry-day” failure (reservoir alone) and a “wet-day” failure (combined with river flooding). It shows the potential extent, not a probability.
How we report it
We check whether your property lies within any mapped reservoir inundation extent, dry-day or wet-day. If it does not — as is the case for the great majority of homes — we report the property as outside the extent and no reservoir figure is shown. If it does fall within an extent, we name the scenario so you understand the context.
What it means for you
Being inside a reservoir inundation extent is not a reason to panic and rarely affects insurance or lending on its own, because the underlying probability is so low. It is, however, useful context: you may be within a formal flood warning area for the reservoir, and it is worth knowing which watercourse or structure is upstream. If the property is outside every extent, this source can be set aside with confidence.
Know the risks before you commit
An instant, plain-English flood & environmental screen for any address in England — a fast, low-cost first look before you spend on surveys or searches.