Beach Dewatering as a 'Soft' Engineering Solution to Coastal Erosion: A History and Critical Review

For over half a century, researchers have reported a link between the elevation of beach groundwater and erosional or accretionary trends at the beach face. Beach dewatering (the artificial lowering of the watertable within beaches by a system of drains and pumps) is proposed by its proponents as a practical alternative to more traditional methods of shoreline stabilization. Within the last 15 years several test sites have been installed, and to date seven commercial dewatering systems have operated. This paper traces the origins and development of the dewatering concept, from early work on beach face permeability and beach groundwater dynamics, to recent field and laboratory studies that have explicitly examined the effect of artificial groundwater manipulation on beach face accretion and erosion. All test and commercial dewatering installations undertaken to date are detailed, and published monitoring results from the two longest-running sites are critically re-assessed. It is concluded that the effectiveness of the dewatering concept in maintaining beach stability and controlling coastal retreat is yet to be convincingly demonstrated at the prototype scale. Some ideas are discussed for further research that may shed light on the underlying physical mechanisms, and if warranted, provide the basis for future design criteria.