Purpose -The aim of this paper is to describe the decision-making framework and datasets behind a national GIS map that assesses the suitability of the subsurface for infiltration sustainable drainage systems (SuDS). In combination they provide geoenvironmental information on the necessary geological and hydrogeological considerations to facilitate preliminary site assessment. Approach -The national suitability map comprises four parts, each of which considers a geoenvironmental factor

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... to SuDS planning, installation and performance. The first three comprise: a) drainage; b) ground stability and c) pollutant attenuation potential. The final map highlights those areas where infiltration may result in negative consequences such as the initiation or exacerbation of flooding or ground instability. Findings -The application of the suitability map is demonstrated for an urban setting showing its relevance to both planning for wide spatial-and site-scale assessment. Research implications -The suitability map aims to provide the data necessary for the assessment of subsurface suitability, rather than a recommendation on the type of infiltration system appropriate to the ground conditions. Future research could address this limitation by incorporating the use of quantitative site-scale information, although it is unlikely that this would be possible at a national-scale. Practical implications -The suitability map is valid for use by developers and planners for the preliminary assessment of sites, but also by unitary authorities for the consideration of planning applications. Originality -This paper introduces an innovative decision-making framework to enable preliminary site assessment for infiltration SuDS and demonstrates the feasibility of the approach through an urban case study.