Risk of Flooding from Surface Water (RoFSW) map is an assessment of where surface water flooding may occur when rainwater does not drain away through the normal drainage systems or soak into the ground, but lies on or flows over the ground instead. It is produced using national scale modelling and enhanced with compatible, locally produced modelling from lead local flood authorities (LLFAs). The RoFSW datasets include information about flooding extents, depths, speed and hazards.
This dataset shows information about flooding extents and depths. The depth of water during a flood is an important factor in how dangerous a flood might be.
RoFSW is a probabilistic product, meaning that it shows the overall risk, rather than the risk associated with a specific event or scenario. In externally published versions of this dataset, risk is displayed as one of three likelihood bandings:
High - greater than or equal to 3.3% (1 in 30) chance in any given year;
Medium - less than 3.3% (1 in 30) but greater than or equal to 1% (1 in 100) chance in any given year;
Low - less than 1% (1 in 100) but greater than or equal to 0.1% (1 in 1000) chance in any given year.
This dataset shows the likelihood of a flood occurring with water at a given depth (or higher). There are separate layers with thresholds for depths of 0m (i.e. flooding extent), 0.2m, 0.3m, 0.6m, 0.9m, and 1.2m.
NB. This is a complex dataset, with preview available only on certain zoom levels. The Web Mapping service has been set to 1:50 000 in the attribute. The services are set to be visible from the 1:50 000 scale range. There may be some variation, since end client software may interpret the request differently. Attribution statement: © Environment Agency copyright and/or database right 2025. All rights reserved.