A number of ‘groundwater flood’ events have been recorded over the Chalk aquifer in southern England since the 1994 occurrence at Chichester, Sussex. Reporting of this event and subsequent groundwater floods indicates that there are two types of groundwater flood event. Type 1 is the true groundwater flood in which the water table elevation rises above the ground elevation, and Type 2 occurs when intense groundwater discharge via bourne springs and highly permeable shallow horizons discharges to surface waters and causes overbank flooding. It is recommended that a Type 1 event be referred to as a true ‘groundwater flood’ and Type 2 simply as a ‘groundwater-induced flood’. Such differentiation will provide a clearer picture for the environmental regulator, the planner and the insurance industry to apply to their own work.

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