Surface Water (Pluvial) Flood Risk outside Flood Plains

Surface water or pluvial flooding occurs as a result of high intensity rainfall which overwhelms natural or man-made drainage systems resulting in water flowing overland and ponding in depressions in the ground. It is a particular problem in urban areas which are often dominated by non-permeable surfaces such as roofs, roads, patios and car parking areas that restrict infiltration of water into the ground and promote run-off. The steady growth of urban areas has served to intensify surface water run-off and to place additional pressures on the piped drainage network. It is not uncommon for drainage systems to be overwhelmed during periods of high intensity rainfall, particularly when blockages occur. The problem is exacerbated in many areas by an outdated drainage infrastructure that has not been upgraded to cope with the rate of development.