Factors Contributing to the Hydrologic Effectiveness of a Rain Garden Network (Cincinnati OH USA)

Abstract

Abstract:Infiltrative rain gardens can add retention capacity to sewersheds, yet factors contributing to their capacity for detention and redistribution of stormwater runoff are dynamic and often unverified. Over a four-year period, we tracked whole-system water fluxes in a two-tier rain garden network and assessed near-surface hydrology and soil development across construction and operational phases. The monitoring data provided a quantitative basis for determining effectiveness of this stormwater control measure. Based on 233 monitored warm-season rainfall events, nearly half of total inflow volume was detained, with 90 percent of all events producing no flow to the combined sewer. For the events that did result in flow to the combined sewer system, the rain garden delayed flows for an average of 5.5 h. Multivariate analysis of hydrologic fluxes indicated that total event rainfall depth was a predominant hydrologic driver for network outflow during both phases, with average event intensity and daily evapotranspiration as additional, independent factors in regulating retention in the operational phase. Despite sediment loads that can clog the rooting zone, and overall lower-than-design infiltration rates, tradeoffs among soil profile development and hydrology apparently maintained relatively high overall retention effectiveness. Overall, our study identified factors relevant to regulation of retention capacity of a rain garden network. These factors may be generalizable, and guide improvement of new or existing rain garden designs.Keywords: wastewater; combined sewer system; hydrologic monitoring; green infrastructure; stormwater detention Highlights •Infiltration-type retention practices can aid in managing stormwater volume. •We monitored a newly-installed rain garden's hydrology over a four-year period.• Rain garden detained 50% of total inflow and delayed overflow to sewer system by~5 h. •Retention effectiveness was related to total inflow volume and intensity, evapotranspiration losses, and soil formation.

Situating Green Infrastructure in Context: A Framework for Adaptive Socio‐Hydrology in Cities

“…Green infrastructure can be broadly defined as green space that promotes access to recreational space, can preserve biodiversity, and leverages continuity of ecosystem processes and functions of ecological systems to regulate and manage technical problems like storm water quality and quantity, as well as urban heat islands (Sandström, ; Tzoulas et al, ). Green infrastructure in many urban planning schemes is, however, principally about storm water management, whether this revolves around flood mitigation, maintaining wastewater system capacity, or water quality improvements to surface waters (Jarden et al, ; Shuster et al, ). To manage storm water, GI enhances retention, infiltration, and evapotranspiration through amendment of soil and plant systems in the urban landscape to redirect water away from wastewater pipes or constructed channels (i.e., gray infrastructure; Berland et al, ; Shuster et al, ; Schifman et al, ).…”

“…Green infrastructure in many urban planning schemes is, however, principally about storm water management, whether this revolves around flood mitigation, maintaining wastewater system capacity, or water quality improvements to surface waters (Jarden et al, ; Shuster et al, ). To manage storm water, GI enhances retention, infiltration, and evapotranspiration through amendment of soil and plant systems in the urban landscape to redirect water away from wastewater pipes or constructed channels (i.e., gray infrastructure; Berland et al, ; Shuster et al, ; Schifman et al, ). Thus, GI acts as an alternative or a complement to centralized gray infrastructure (Fletcher et al, ) practices by offering these typically overburdened collection systems additional detention capacity.…”

Managing Uncertainty in Runoff Estimation with the U.S. Environmental Protection Agency National Stormwater Calculator

“…In particular, runoff from residential and commercial parcels and properties can constitute a considerable proportion of stormflow volume, yet holds much potential for management with LID and GI techniques applied to parcels, neighborhoods, and in right‐of‐way areas (Green et al ., ; Shuster and Rhea, ; Herrmann et al ., ; Jarden et al ., ; Schifman et al ., ; Shuster et al ., ). Any type of GI installation is a hydrologic intervention, and more often than not, requires hydrologic modeling to support the planning and design process.…”

“…Urban landscapes present the ongoing challenge of dealing with stormwater runoff volume generated from impervious surfaces (Arnold and Gibbons, 1996;Lee and Heaney, 2003;Shuster et al, 2005;Gilbert and Clausen, 2006;Chen et al, 2017). The advent of green infrastructure (GI) for stormwater management marks a transition from centralized wastewater-stormwater collection systems that route runoff into gray infrastructure (Delleur, 2003;Cherrier et al, 2016), to decentralized low-impact development (LID) and GI techniques that are placed to manage and detain runoff at the scale of a residential or commercial parcel (Parikh et al, 2005;Jarden et al, 2016;Shuster et al, 2017). The overarching philosophy of GI and LID entails mitigating against runoff formation (as infiltration-excess, or saturation-excess mechanisms), and retaining runoff volume as close to its point of generation as possible.…”

“…In particular, runoff from residential and commercial parcels and properties can constitute a considerable proportion of stormflow volume, yet holds much potential for management with LID and GI techniques applied to parcels, neighborhoods, and in right-of-way areas (Green et al, 2012;Shuster and Rhea, 2013;Herrmann et al, 2016;Jarden et al, 2016;Schifman et al, 2016;Shuster et al, 2017).…”