Flood Risk Assessments for Small Catchments Under Climate Change—How Can Scotland Improve Its Policy for Enhanced Flood Resilience and Preparedness

Flood risk assessments (FRAs) are essential tools in Scottish planning policy to identify and minimise flood risk in new planning applications. Most FRAs in Scotland are performed in (very) small (< 50km²) < 100km² catchments, particularly vulnerable to increases in rainfall intensity due to climate change. This study provides a historical overview of the literature used as guidance in FRAs in Scotland and then focuses on their application in smaller catchments, addressing three areas: understanding the different physical processes in smaller catchments, their representation within the guidelines and how these guidelines are applied in practice. Our results highlight the need to move beyond simple mathematical and hydrological methods for FRAs. We find that small catchments' physical processes are not adequately represented in current methods, leading to higher biases and uncertainties in modelling. When applied in practice, these techniques are often used unconventionally for the fulfilment of established guidelines. Finally, climate change science implementation into guidance also needs refinement, with current regulations lacking a sound scientific basis, particularly for smaller catchments. We underscore the need for testing and application of innovative solutions found in academia and utilisation of additional data to provide improved methods for FRAs in smaller catchments, particularly under climate change.