Development of a suitability map for infiltration sustainable drainage systems (SuDS)

Infiltration sustainable drainage systems (SuDS) such as soakaways and permeable pavements use the capacity of the subsurface to attenuate surface water. The implementation of SuDS is required by the Floods and Water Management Act 2010, and the associated National Standards for Sustainable Drainage prioritise infiltration over other surface water drainage methods. This paper describes the development of a nationally derived Infiltration SuDS Map that enables preliminary assessment of the suitability of the ground for infiltration SuDS. It shows that national geological and hydrogeological datasets, developed by the British Geological Survey, can be used to support early planning decisions. The map comprises 24 GIS layers that both summarise and provide subsurface information on the suitability of the ground with respect to significant flooding and stability constraints, the drainage potential and considerations relating to ground stability and groundwater protection. The map was validated using an independent database of SuDS installations and was found to accurately describe the ground conditions in all 27 cases. The Infiltration SuDS Map suggests that 34.5 %of the United Kingdom is suitable or probably suitable for free-draining SuDS, but that the potential for infiltration SuDS at the city-scale varies depending on the ground conditions. For example, 60 % of Bradford was deemed as suitable, or probably suitable for Infiltration SuDS, whereas only 19 %of the area of Leicester was similarly classified.