Stormwater management network effectiveness and implications for urban watershed function: A critical review

Abstract

Deleterious effects of urban stormwater are widely recognized. In several countries, regulations have been put into place to improve the conditions of receiving water bodies, but planning and engineering of stormwater control is typically carried out at smaller scales. Quantifying cumulative effectiveness of many stormwater control measures on a watershed scale is critical to understanding how small‐scale practices translate to urban river health. We review 100 empirical and modelling studies of stormwater management effectiveness at the watershed scale in diverse physiographic settings. Effects of networks with stormwater control measures (SCMs) that promote infiltration and harvest have been more intensively studied than have detention‐based SCM networks. Studies of peak flows and flow volumes are common, whereas baseflow, groundwater recharge, and evapotranspiration have received comparatively little attention. Export of nutrients and suspended sediments have been the primary water quality focus in the United States, whereas metals, particularly those associated with sediments, have received greater attention in Europe and Australia. Often, quantifying cumulative effects of stormwater management is complicated by needing to separate its signal from the signal of urbanization itself, innate watershed characteristics that lead to a range of hydrologic and water quality responses, and the varying functions of multiple types of SCMs. Biases in geographic distribution of study areas, and size and impervious surface cover of watersheds studied also limit our understanding of responses. We propose hysteretic trajectories for how watershed function responds to increasing imperviousness and stormwater management. Even where impervious area is treated with SCMs, watershed function may not be restored to its predevelopment condition because of the lack of treatment of all stormwater generated from impervious surfaces; non‐additive effects of individual SCMs; and persistence of urban effects beyond impervious surfaces. In most cases, pollutant load decreases largely result from run‐off reductions rather than lowered solute or particulate concentrations. Understanding interactions between natural and built landscapes, including stormwater management strategies, is critical for successfully managing detrimental impacts of stormwater at the watershed scale.

Changes in event‐based streamflow magnitude and timing after suburban development with infiltration‐based stormwater management

“…The speed of SCM installation in suburban and urban watersheds has outpaced our understanding of how effective watershed‐scale installation of SCMs is for mitigating streamflow response to precipitation events. There are few empirical, watershed‐scale studies of the hydrologic impacts of installing a network of SCMs, and modelling studies may overestimate the effect of SCM treatment on stormflow response (Jefferson et al, ; Li, Fletcher, Duncan, & Burns, ). Therefore, there is a critical need for empirical monitoring to assess and validate the hydrological performance of watershed‐scale SCM implementation, rather than a reliance on individual SCM performance and modelling studies.…”

“…The speed of SCM installation in suburban and urban watersheds has outpaced our understanding of how effective watershed-scale installation of SCMs is for mitigating streamflow response to precipitation events. There are few empirical, watershed-scale studies of the hydrologic impacts of installing a network of SCMs, and modelling studies may overestimate the effect of SCM treatment on stormflow response (Jefferson et al, 2017;Li, Fletcher, Duncan, & Burns, 2017).…”

Modeling Runoff and Nitrogen Loads From a Watershed at Different Levels of Impervious Surface Coverage and Connectivity to Storm Water Control Measures

“…This is a substantial reduction and again emphasizes the potential for SCMs to offset increased NO 3 loads from increases of impervious surface during urban development. This effect of SCMs on NO 3 loads has been shown in empirical studies (Hale et al, ; Pennino et al, ), but the number of watershed scale studies like this are limited (Jefferson et al, ). The effects of SCM connectivity on N loads are also amplified in warmer months relatively to cooler ones (Figures b and c).…”

“…Modeling studies have shown that EI predicts runoff volumes and storm event peak discharges well (Dewals et al, ; Guo, ; Lee & Heaney, ; Palla & Gnecco, ; Schoener, ; Shields & Tague, ). However, there is currently a lack of empirical studies examining the watershed‐scale effects of connectivity to SCMs on water quality, and only a few modeling studies exist (Jefferson et al, ).…”

Conceptualization and Schematization of Mesoscale Sustainable Drainage Systems: A Full-Scale Study

“…This can be done by characterizing SCMs as well as understanding their cumulated affect in a larger system, which is reported to be challenging and empirically less attended [17].…”