Mitigating floods and attenuating surface runoff with temporary storage areas in headwaters

Temporary storage areas (TSAs) represent a category of soft-engineered nature-based solutions that can provide dispersed, small-scale storage throughout a catchment. TSAs store and attenuate surface runoff, providing new additional storage during flood events. The need for such additional catchment storage will become more urgent as the frequency and magnitude of extreme hydrological events increases due to climate change. Implementation of TSAs in headwater catchments is slowly gaining momentum, but practitioners still require further evidence on how such measures function during flood events. This review focuses on the role of relatively small-scale (<10,000 m(3)) TSAs in headwater catchments for flood risk management. It also explores the potential wider benefits for implementing these as part of an integrated catchment management approach. TSA flood mitigation effectiveness is primarily determined by the TSA's available storage prior to the event. At the local scale, this can be represented by the relationship between TSA inputs, outputs and total storage. Factors influencing the local functioning and effectiveness of TSAs are discussed, with potential considerations for optimizing future TSA design and management. Hydrological models have suggested that TSAs could be used to effectively attenuate high magnitude events. However, future considerations should involve addressing the lack of empirical evidence showing TSA catchment scale effectiveness and how local TSA functioning might change in time. Small-scale headwater TSAs offer a holistic and sustainable approach to catchment management that can deliver both local benefits to landowners and wider flood risk mitigation for society.This article is categorized under:Engineering Water > Sustainable Engineering of WaterScience of Water > Water ExtremesScience of Water > Hydrological Processes

Automated summary

Temporary storage areas (TSAs) are nature-based solutions that can store and attenuate surface runoff, providing additional storage during flood events in a catchment. The implementation of small-scale TSAs in headwater catchments is gaining momentum, but further evidence is needed on their effectiveness during flood events. This review examines the role of small-scale TSAs in flood risk management and explores their potential benefits in integrated catchment management. Factors influencing TSA functioning and effectiveness are discussed, along with considerations for future design and management.