Using Storage Ponds in Natural Flood Management Schemes in Practice: The Need for Fine-Tuning and Upscaling

Abstract

There is increasing interest in installing water storage ponds as part of natural flood management (NFM) approaches being implemented globally. Despite decades of experience with constructing flood storage ponds within civil engineering disciplines, there remains little empirical evidence of their effectiveness in NFM. In NFM, ‘natural’ ponds use green infrastructure, are often smaller but more numerous, and are built and maintained by land managers rather than engineers. Here we investigate six flood storage ponds in the 69 km² Eddleston NFM pilot catchment in Scotland, UK, analysing impact on peak stream flows at different scales and pond designs. The ponds generally reduce peak stream flows where they have large available capacity, catchments are small (< 1 km²), and events are low magnitude (> 20% Annual Exceedance Probability (AEP)). No discernible flow reduction was observed at the largest pond and catchment (64 km²) for the largest (~21% AEP) event. There was significant variability between ponds, and gains can be made in engineering pond inlet/outlet structures, maintenance, and more widespread installation. The findings suggest that natural storage ponds have most potential to contribute to flood control in small catchments (< 10 km²) and small flood events (> 25% AEP), when they are carefully designed and maintained, and sufficient in number.