Timm, A., V. Ouellet, and M. Daniels. 2020. River Research and Applications 36(10): 1973-1984.
Green infrastructure (GI) and other stormwater management practices are commonly designed to reduce stormflow volume and pollutant loads by using infiltration, retention, and evapotranspiration to capture stormwater. Although these methods are be designed to reduce impacts of stormwater volumes and pollutant loads, they may not be designed to mitigate thermal load from stormwater runoff in urban areas. This review of literature identifies key drivers of stream temperature in urban streams, including heat transference from stormflow and effects of pipe networks and evapotranspiration on baseflow. Recent simulation studies indicate the need for more than bioretention, increased infiltration, and tree canopy mitigation practices to reduce heat stress in urban streams. These studies show greatest reductions in thermal load by applying cool surfaces as a single thermal mitigation practice (TMP) and comprehensive applications of TMPs to all available areas at the watershed scale. This review of available literature suggests that incorporating TMPs into current and future GI designs will help maintain water resources, water quality, aquatic ecosystems, and coldwater stream species across the landscape. Further research is needed on the most effective ways to implement TMPs as part of our current and future GI designs for stormwater and how to best incorporate these measures into urban design concepts at larger spatial scales.