<scp>TSA</scp> ‐ <scp>DOT</scp> : A Decision Support Tool for Designing and Optimising Nature‐Based Solutions for Flood Mitigation

ABSTRACT Nature‐based solutions, such as temporary storage areas (TSAs), are increasingly implemented within natural flood management strategies to mitigate flooding and soil erosion by attenuating surface runoff during storm events. However, guidance on optimising site‐specific TSA designs for runoff attenuation remains limited, and no existing approach comprehensively evaluates TSA effectiveness across multiple flood mitigation metrics. This study addresses these gaps by introducing the TSA Design Optimiser Tool (TSA‐DOT), a decision support tool for designing and optimising TSAs as effective nature‐based solutions for runoff attenuation, contributing to flood mitigation. The tool evaluates TSA performance using five flood mitigation metrics: storage efficiency index, mean retention time, peak flow attenuation, peak flow reduction, and changes in peak flow travel time. It incorporates site‐specific data such as topography and potential storage capacity, soil infiltration rates, and design storm events. Users can prioritise and customise flood mitigation metrics, making the tool suitable for a wide range of catchment settings. When applied at two agricultural TSA sites in northeast Scotland, the tool identified the importance of optimising storage‐to‐drainage relationships for effective runoff attenuation and highlighted the need for increased storage capacity or drainage adjustments under extreme storm events or limited soil infiltration. TSA‐DOT provides practical guidance for using TSAs as part of flood risk management, with integration potential into catchment‐scale hydrological models for scalable, site‐specific applications.