Reservoir inundation maps: wet day and dry day

Reservoir inundation maps show the predicted extent of flooding if a large raised reservoir failed. They are not probability maps and they do not mean failure is likely. Dry day mapping models failure when rivers are at normal levels. Wet day mapping models failure when rivers are already in flood, so it usually shows a worse combined scenario.

Reservoir inundation maps are credible worst case modelling outputs showing where water could go if a large raised reservoir failed. A dry day scenario assumes reservoir failure when local rivers are at normal levels. A wet day scenario assumes reservoir failure when rivers are already experiencing extreme natural flooding. Buyers should use these maps as emergency and residual risk context, not as a forecast of likely flooding.

• GOV.UK: Reservoir flood maps, when and how to use them


• Data.gov.uk: Reservoir Flood Extents, Dry Day


• Environment Agency: Reservoir Flood Extents, Wet Day

Reservoirs, Inundation, Emergency planning

Reservoir failure map, Wet day scenario, Dry day scenario