Mapping national-scale fluvial flooding for SEPA
HR Wallingford developed a flood map for SEPA that provides a strategic national overview of flooding. It is also intended to help improve public awareness of flood risk and to encourage actions that reduce this risk. Local authorities can use the information to be proactive in their responsibilities for managing flood risk – better awareness of which land is at risk of flooding means that they can develop their flood risk management strategies in effective combination with SEPA’s flood warning role. The mapping system will also help in planners locating of new homes, businesses and other developments taking into account flood risk.
We applied a suite of tools to the whole of Scotland to produce flood outlines. These included GTI Floodplain (an internal GIS-based tool comprising detailed data manipulation routines), the Conveyance Estimation System and the InfoWorks RS modelling software. Flood outlines were produced for return periods of 100, 200 and 1000 years. The scale of a flood depends on factors such as the amount and intensity of rainfall and catchment conditions (hilly/vegetated, how dry or wet the ground is). Independent coastal flood outlines were also incorporated.
The website shows river and coastal flooding, and flood defence scheme assets. Multimap mapping technology was combined with SEPA’s flooding data, to create a single interface where citizens, investors, and property planners, can visualise the flooding risk areas on map, at a glance. The flood hazard maps (up to 1:25,000 scale) cover the whole of Scotland, including all river reaches with catchments greater than 3 km2. A second layer shows the defence assets.
Local authorities can use the information to be proactive in their responsibilities for managing flood risk