Description: The groundwater flooding susceptibility data shows the degree to which areas of England, Scotland and Wales are susceptible to groundwater flooding on the basis of geological and hydrogeological conditions. It does not show the likelihood of groundwater flooding occurring, i.e. it is a hazard not risk-based dataset. The data covers Great Britain in a consistent manner. It will be updated periodically (at least bi-annually) as the underlying datasets or the methodology to derive the groundwater flooding susceptibility data are improved. The data is based on data sets with a range of resolutions, but the derived data set has an effective spatial resolution of about 50m by 50m.
The data has been produced using a 'rule-based' approach. The first step was to apply 'rules' to identify areas, based on geological considerations, where groundwater flooding could not occur, i.e. areas where non-aquifers are present at the ground surface. For all areas that were geologically susceptible, a second suite of rules was used to produce a national groundwater level surface using data taken from published BGS groundwater level contours, groundwater levels in BGS WellMaster database and inferred from some river levels. A further suite of rules was used to modify this groundwater level surface so that it was representative of conditions of groundwater flooding. Finally, this modified groundwater surface was compared with a digital terrain model (DTM) of the ground surface elevation and a final set of rules was used to zone the degree of susceptibility depending on the modelled depth of the groundwater surface below the land surface.
The susceptibility data is suitable for use for regional or national planning purposes where the groundwater flooding information will be used along with a range of other relevant information to inform land-use planning decisions. It might also be used in conjunction with a large number of other factors, e.g. records of previous incidence of groundwater flooding, rainfall, property type, and land drainage information, to establish relative, but not absolute, risk of groundwater flooding at a resolution of greater than a few hundred metres. In all cases it is strongly recommend the confidence data is used in conjunction with the groundwater flooding susceptibility data. The susceptibility data should not be used on its own to make planning decisions at any scale, and, in particular, should not be used to inform planning decisions at the site scale. The susceptibility data cannot be used on its own to indicate risk of groundwater flooding
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