Sensitivity of Streamflow Metrics to Infiltration‐Based Stormwater Management Networks

Abstract

As stormwater control measures (SCMs) capture surface runoff from impervious areas, a shift in the water balance and flow regime components may emerge in urban watersheds, but the amount of SCM treatment needed to detectably shift these components may vary. We used the Soil and Water Assessment Tool (SWAT) hydrologic model to assess the sensitivity of 16 hydrologic metrics as an increasingly dense rain garden SCM network was applied across the West Creek watershed, near Cleveland, Ohio (USA). As the area treated by SCMs increased, annual baseflow increases matched decreases in surface runoff, while water yield and evapotranspiration changes remained small. The stream's peak response to rainfall decreased with SCM implementation across storm sizes, ranging from the threshold rainfall depth (4.8 mm) to values higher than the design storm of a single rain garden (19 mm). SCM networks draining >20% of directly connected impervious area (DCIA) significantly decreased the magnitude of discharges with a return period of less than 1 year, the percentage of time above mean flow, and flashiness. Recession slopes and annual 1‐ and 7‐day low flows exhibited a slight response that fell within uncertainty limits of the model. Water balance and rainfall response metrics exhibited the greatest sensitivity to different intensities of stormwater management, while infrequent high and low flows were resistant to detectable change even at high levels of SCM treatment when model uncertainty was included.

Effects of Design and Climate on Bioretention Effectiveness for Watershed-Scale Hydrologic Benefits

“…S43-S51(a and b). Differences in storm duration, rainfall distribution through time, and, perhaps most important, antecedent rainfall all affect runoff characteristics and GSI performance (Avellaneda and Jefferson 2020). While using a design storm approach is attractive in its simplicity, it may not provide an accurate assessment of bioretention effectiveness.…”

“…Our work provides additional insight into the role of bioretention size, soil infiltration rate, storm size, and climate in GSI performance. Other factors, including watershed size and shape, land use, topography, and in situ soil types also affect GSI effectiveness and deserve further research (Avellaneda and Jefferson 2020;Lewellyn and Wadzuk 2019). There has been recent work on assessing GSI performance under climate change (Tirpak et al 2021), but at the site rather than the watershed scale.…”

“…Despite substantial research on the effectiveness of individual bioretention areas, it is still unclear how to best implement these practices to achieve watershed-scale benefits (Golden and Hoghooghi 2017; Jefferson et al 2017). Monitoring (Hopkins et al 2019;Loperfido et al 2014;Woznicki et al 2018) and modeling studies (Avellaneda and Jefferson 2020;Fry and Maxwell 2017;Wright et al 2018) have shown that extensive systems of GSI can have measurable watershed-scale benefits. However, some found relatively minor benefits (Avellaneda et al 2017;Hoghooghi et al 2018), while others found more impressive GSI performance (Fry and Maxwell 2017;Wright et al 2018).…”

“…In some cases, stormwater controls may have no discernable benefit at the watershed scale (Miller et al 2021). The reasons for these discrepancies vary, but are likely due primarily to differences in climate, storm event size, and the type and extent of GSI implemented (Avellaneda and Jefferson 2020). For example, GSI performance tends to decrease as storm size increases (Bell et al 2020;Hopkins et al 2019), although effectiveness in large storms (e.g., 100-year events) has 1 Assistant Professor, School of Engineering and Technology and Institute for Great Lakes Research, Central Michigan Univ., Mt.…”

“…Email: rod.lammers@cmich.edu 2 Student, Geography and Environmental Studies, Univ. of Madison,WI 53706. been found to vary markedly depending on climate (Avellaneda and Jefferson 2020;Fry and Maxwell 2017;Hu et al 2019). Other climate characteristics beyond storm size (e.g., potential evapotranspiration, interstorm duration) can also affect performance (Voter and Loheide 2021).…”