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Government policy for England is to introduce sustainable drainage systems (SuDS) to control site rainfall runoff via conditions in planning approvals. Infiltration into the ground is the preferred method for managing surface water runoff on site without increasing flood risk downstream.
Property professionals need to assess the feasibility of infiltration SuDS at an early stage in support of the site development process. This will allow outline site assessment of the cost implications and initial master planning of the development prior to the requirement for detailed design.
Lead Local Flood Authorities also need clear guidance on the site suitability for infiltration SuDS when they are assessing proposed developments.
The GeoSmart SD50 map provides an assessment of the capacity of the ground to receive infiltration depending on the nature, thickness and permeability of the underlying material and the depth to the high groundwater table.
Government policy across the UK is to introduce sustainable drainage systems (SuDS) to control site rainfall runoff via conditions in planning approvals. A range of SuDS options are available, but guidance states that infiltration into the ground, where feasible, is the preferred method for managing surface water runoff on site without increasing flood risk downstream. Regulations on SuDS vary locally, and should be verified with your local planning authority.
The GeoSmart SuDS Infiltration Suitability Map should be consulted as part of the site development and design process or when considering land purchase.
The SuDS map supports the following requirements:
The map provides an initial assessment of the feasibility of infiltration SuDS at a site and recommendations on site investigations to support Infiltration system design, where relevant. It is intended to support property professionals at an early stage in the development planning process in understanding the SuDS options available at a site and the risks and costs associated with them.
A sustainable drainage system (SuDS) is designed to replicate, as closely as possible, the natural drainage from the Site (before development) to ensure that the flood risk downstream of the Site does not increase as a result of the land being developed. SuDS can also significantly improve the quality of water leaving the Site and can enhance the amenity and biodiversity that a site has to offer.
There are a range of SuDS options available to provide effective surface water management that intercept and store excess runoff. When considering these options the preferred destination of the run off should be assessed using the order of preference outlined in the Building Regulations Part H document (HM Government, 2010) and DEFRA’s Draft National Standards for SuDS (2011):
For general information on SuDS see www.susdrain.org.
The GeoSmart SuDS Infiltration Suitability Map has full coverage over Great Britain with a resolution of 50m.
The GeoSmart SuDS Infiltration Suitability Map map consists of an Infiltration Potential Map which represents three categories, Low, Moderate, High, which indicate the potential for successfully implementing an infiltration system at a given location. The mapped infiltration potential is based on data related to the geology of underlying superficial deposits and bedrock, their permeability, the thickness of the superficial deposits, where they exist, and high groundwater levels.
For sites less than 1 ha, a close-up of the Infiltration Potential map for the site can be obtained via the SuDSmart Standard, Plus and Pro Reports, along with site analyses and recommendations related to site investigations to inform infiltration system design and additional supporting information. For larger sites, the GeoSmart SuDS Infiltration Suitability Map can be obtained for any area boundary. The map is also available for purchase at county or national scale.
The map will tell you whether infiltration is likely to be a feasible solution for managing rainfall runoff at your site. Where relevant, it will also provide information that supports the initial conceptual design of an infiltration system and recommendations on field investigations required to support the detailed design of such a system. Whether infiltration techniques are feasible or not will determine the suitability of other SuDS schemes going forward. The map can therefore provide information early on in the property development process related to the range of SuDS options available to a site and expected costs of implementing SuDS at a site.
The GeoSmart SuDS Infiltration Suitability Map incorporate various national scale datasets including 1:50,000 scale Geological Maps produced by the British Geological Survey and Permeability Data and Superficial Deposit Thickness. GeoSmart’s SuDS Infiltration Suitability Map also uses information from GeoSmart’s Groundwater Flood Risk Map, which is based on national scale datasets of topography and groundwater levels, in addition to bespoke in-house hydrogeological and risk models.
The map is updated on a 6-month cycle to take advantage of newly released data as soon as it comes out.
The map has been through a rigorous internal QA process. At every update cycle, it is reviewed against a national database of site-specific SuDS assessments to verify its validity and identify any required model improvements to be incorporated into the next updated release.
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