Impact of climate change on the flow regime of a Cleveland, Ohio, urban stream: implications for stormwater management

Abstract:

Continuous changes in precipitation patterns and rising air temperatures due to climate change are expected to have a significant impact on both high and low streamflows. In urban streams, these climate-induced changes potentially further exacerbate the challenges of stormwater management and urban flooding. We evaluate the impact of projected 21st century climate change on the flow regime of a 20.6 km2, 30.3% impervious urban watershed near Cleveland, Ohio, using a calibrated hydrological model (PCSWMM). 1-hour historical (1976-2000) and future climatic (2021-2095, RCP 8.5) precipitation and temperature outputs of four regional climate models (RCMs) were obtained from NA-CORDEX, bias-corrected to historical observed data using quantile mapping, and disaggregated to 15-minute temporal resolution for precipitation. Results from the four RCMs project mean air temperature increases in Cleveland of 1.7 ^oC, 3.2 ^oC, and 5.0 ^oC for near-term (2021-2045), mid (2046-2070), and late (2071-2095) century intervals, respectively. Similarly, there is an increasing trend of mean annual precipitation increases by 15-20%, 15-37%, and 23-48% in the same intervals. In the urban stream, climate change increases discharge throughout the flow-duration curve, with a dramatic increase between historical and near-term and less change between near-term and late century. The largest relative change between historical and near-term is in moderately high flows (15-30% exceedance), whereas later in the century low flows experience the largest change. The largest flood in each 25 year period also increases by 4% to 57%, with a maximum increase during mid-century. Variability among the RCMs is small relative to the predicted changes, particularly for the near-term. The substantial change in peak flows and total flows will lead to increasing flood risk and decreasing performance of existing green infrastructure. Installation of new green infrastructure, sized appropriately for future climates, across the catchment may help mitigate some of the adverse effects of climate change.