Implementation of the Flood and Water Management Act (2010) will place increased responsibility on local planning authorities (LPAs) in England for planning approval and future maintenance of sustainable drainage (SUDS) installations. LPAs have limited experience in assessing SUDS, and there is a need for additional guidance to support decision making. A method was developed to analyse environmental and institutional characteristics of existing published datasets using a Geographical Information System (GIS), and to create maps indicating feasible locations for SUDS devices at the strategic scale of a full LPA area. The method was applied to an example study site: Coventry, UK, covering 98.7 km2, of which 33% was impermeable, estimated from Ordnance Survey land cover. The method was reliant on the accuracy of the underlying datasets, although data uncertainties were identified, e.g. the incorrect classification of some land cover and lack of definition in private gardens. Construction of a framework allowed a structured approach to collection and presentation of information, and is a point of reference for other strategic scale investigations of SUDS feasibility. Feasibility maps were generated for SUDS in new developments, on both greenfield and previously developed land, and for retrofit of existing developments, across five main categories of SUDS: source control, infiltration, filtration, conveyance, and detention & retention. In new developments, source control, filtration and detention & retention SUDS were possible in 99% of Coventry, filtration SUDS in 95% and infiltration solutions 17%. The higher number of restrictions imposed on retrofit resulted in a smaller area where SUDS were feasible: source control 68%, infiltration 11%, filtration 64%, conveyance 57% and detention 79%. Soil impermeability and depth to water table were the principal spatial limitations on infiltration and detention SUDS in new developments. Water bodies imposed the small number of restrictions on source control, filtration and conveyance in new developments. Existing land cover was the main driver of feasible locations for retrofit. Smaller parcels of land were available for retrofit (median 35 m2) than for new development (median 100 m2). Private gardens occupied 23% of the city, forming a large part of suburban land cover. Large scale retrofit in these areas would necessitate convincing a significant number of individual landowners of the benefits of SUDS. Use of feasibility maps created using the method developed in this research might encourage more specific and earlier consideration of SUDS in the planning process. Retrofit feasibility maps, in conjunction with datasets identifying problem locations, would assist strategic reviews of SUDS options.
- Local Planning Authority
- new development