Evaluating the impact of climate change on future bioretention performance across the contiguous United States

In light of shifting precipitation patterns induced by climate change, communities are seeking to build resiliency in urban drainage systems through interventions such as green stormwater infrastructure (GSI). Bioretention cells are one of the most commonly implemented forms of GSI for their ability to reduce peak discharge, retain runoff, and filter pollutants. However, they may be at risk of reduced function in the future due to deviations from historic precipitation frequency and intensity patterns which are essential to their design. Further, changes in future function are likely to vary regionally as the magnitude of future climate changes will differ across the globe. To explore the range of impacts to future bioretention function, an ensemble of 10 regional climate models at 17 locations across the contiguous United States were evaluated to provide the widest range of potential future outcomes using a probabilistic approach to capture the uncertain nature of climate change. Bioretention cells were modeled using USEPA's Storm Water Management Model (SWMM) to compare existing and future per-formance under a range of climate change projections. Median annual rainfall and 99th percentile rainfall event depths and intensities were projected to increase across all 17 locations while antecedent dry period (i.e., the time between consecutive rain events) was projected to increase for 11 locations. Correspondingly, bioretention cell hydrologic performance decreased across all 17 locations under future scenarios: relative to performance under current climate conditions, annual volumes of infiltration decreased between 4.0 and 24.0% across all 17 locations while overflow increased between 0.4 and 19.6% for 15 locations. Results suggest that bioretention cells in the southern United States are at significant risk of reduced function in the future while those in the Midwest and Northeast are at moderate risk. Bioretention cells in the Northwest/West performed the best under future climate scenarios; that is, they showed similar function in the future to that of the present. Findings demonstrate that most, if not all, bioretention cells across the contiguous United States will require some degree of modification to maintain existing function under future conditions.

Automated summary

Due to climate change, communities are using interventions like green stormwater infrastructure (GSI) to enhance the resilience of urban drainage systems. Bioretention cells, a common form of GSI, are at risk of reduced function in the future due to deviations from historic precipitation patterns essential to their design. To explore the impacts, an ensemble of climate models were used to compare current and future performances of bioretention cells under different climate change projections.