Where can surface water be drained into the ground sustainably (Infiltration SuDs)?
Following the floods of 2007, the Floods and Water Management Act 2010 provided a strategy for resolving issues of surface water flooding. The Act and the associated DEFRA National Standards for Sustainable Drainage Systems (SuDS), aim to
minimize surface water flooding and deterioration to river water quality by dealing with rainwater near to where it falls. The Act requires that SuDS are installed in new developments from April 2014 onwards. The priority mechanism for drainage is infiltration of surface water to the ground, for example via soakaways or permeable pavements. Because the installation and design of these infiltration SuDS is highly dependent on the properties of the ground, information is needed on where the ground will drain effectively without causing flooding or ground stability hazards.
The British Geological Survey’s Infiltration SuDS Map enables a preliminary assessment of the suitability of the ground for infiltration. It provides information on the drainage potential of the ground by estimating the depth to groundwater, subsurface permeability and highlights the presence of floodplains. It identifies the potential for hazards associated with soluble rocks, landslides, compressible and collapsible ground, shallow mining hazards, swelling clays and running sands, which may arise as a result of infiltrating water into the ground. It also highlights the occurrence of the Environment Agency’s source protection zones, the presence of made ground and the method by which water moves through the unsaturated zone (fracture or intergranular flow). This information helps in the design of a drainage system that will protect groundwater quality.
In 2013, the Infiltration SuDS Map won the Sustainable Drainage & Flood Management Initiative of the Year at the Water Industry Achievement Awards, the judges were"impressed with British Geological Survey’s Infiltration SuDS Map … it could have a wide and major impact on the whole country as it improves on best practice…."
The British Geological Survey’s Infiltration SuDS Map allows users to make a preliminary assessment of the suitability of the subsurface for infiltration SuDS. It has been used by water companies to pre-select potentially suitable locations avoiding the need for expensive site investigations where infiltration is unlikely to be possible. It has also been used by consultants to help plan site investigations and develop site layouts; however the most frequent user of the Map has been the SuDS Approval Bodies within local authorities, who have the remit to approve incoming applications for sustainable drainage. The map is beneficial because it allows local authority drainage engineers to easily determine whether site conditions are potentially suitable for infiltration and identify factors that should be taken into account during investigations.
The British Geological Survey is currently undertaking research to study the impacts of infiltrating water to the ground on groundwater levels at the catchment scale. In addition, research at the site-scale is being undertaken to understand whether surface water drained through infiltration SuDS could impact groundwater quality.Add Pingback