Assessing the effects of climate change on urban watersheds: a review and call for future research

Considerable efforts have been made to control and manage hydrology and water quality of watersheds impacted by urban development through construction of stormwater control measures (SCMs). Climate change (CC) could, however, undermine these efforts through intensifying precipitation and hydrologic extremes. Although the impact of CC on water resources has been well-documented, its impact on urban hydrology remains less studied. CC may complicate sustainable urban hydrology, which can cause reduction in SCM efficiency with changes in precipitation pattern (i.e., change in duration, frequency, depth, and intensity). More intense precipitation may result in reduced runoff reduction and treatment efficiency given that SCMs have the finite surface storage volume and surface infiltration capacity. Determining the functionality of various SCMs under future climate projections is important to better understand the impact of CC on urban stormwater and how well these practices can build resiliency into our urban environment. The purpose of this review is to provide the needs and opportunities for future research on quantifying the effect of CC on urban SCMs and characterizing the performance and effectiveness of these systems under existing and projected climate scenarios. A summary of the modeled constituents as well as the stormwater and climate models applied in these studies is provided. We concluded that there are still limitations in exploring the impact of future change in meteorological variables will influence the operation of SCMs in the long-term. Previous studies mostly focused on the impacts of CC on urban runoff quantity and only handful studies have explored water quality impacts from CC such as potential changes in water temperature, metals and pathogens. Assessing pollutant removal efficiency of SCMs such as bioretention, infiltration trenches, dry and wet swales, rooftop disconnections, wet and dry ponds, which are common practices in urban watersheds, also needs more attention. Analysis on the cost of adapting SCMs to CC to maintain the same performance as current climate conditions is also recommended for future research.