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Evaluating Retention Capacity of Infiltration Rain Gardens and Their Potential Effect on Urban Stormwater Management in the Sub-Humid Loess Region of China

DOI:10.1007/s11269-015-1206-5
Authors:
Shuan Tang at Yangzhou University
Shuan Tang
Wan Luo at Yangzhou University
Wan Luo
Zhonghua Jia at Xi'an University of Technology
Zhonghua Jia
Wenlong Liu at Yangzhou University
Wenlong Liu
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Abstract and Figures

Recognized as an effective low impact development (LID) practice, rain gardens have been widely advocated to be built with urban landscaping for stormwater runoff reduction through the retention and infiltration processes; but the field performance and regional effect of rain gardens have not been thoroughly investigated. In this paper, we presented a four-year monitoring study on the performance of a rain garden on stormwater retention; hydrological models were proposed to predict the potential effect of rain gardens on runoff reduction under different storms and the future urban development scenarios. The experimental rain garden was constructed in a sub-humid loess region in Xi’an, China; it has a contributing area ratio of 20:1 and depth of 15 cm. During the study period, we observed 28 large storm events, but only 5 of them caused overflow from the rain garden. The flow reduction rate for the overflow events ranged from 77 to 94 %. The runoff coefficient from the contributing area (RC) was reduced to less than 0.02 on annual basis, and 0.008 over the four years average. Field observations also showed that infiltration rate remained stable during the operation period. The predictions based on the future landuse and storm variability of the study area showed that by converting a small fraction of the city land area into rain gardens, the negative hydrological effect from expansion of impervious area can be reduced significantly. The challenge, however, lies in how to plan and build rain gardens as an integral part of the urban landscape.
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Evaluating Retention Capacity of Infiltration Rain
Gardens and Their Potential Effect on Urban Stormwater
Management in the Sub-Humid Loess Region of China
S. Tang
1
&W. Luo
2
&Z. Jia
2
&W. Liu
3
&S. Li
1
&Y. Wu
1
Received: 29 September 2015 /Accepted: 25 November 2015 /
Published online: 2 December 2015
#Springer Science+Business Media Dordrecht 2015
Abstract Recognized as an effective low impact development (LID) practice, rain gardens
have been widely advocated to be built with urban landscaping for stormwater runoff reduction
through the retention and infiltration processes; but the field performance and regional effect of
rain gardens have not been thoroughly investigated. In this paper, we presented a four-year
monitoring study on the performance of a rain garden on stormwater retention; hydrological
models were proposed to predict the potential effect of rain gardens on runoff reduction under
different storms and the future urban development scenarios. The experimental rain garden
was constructed in a sub-humid loess region in Xi’an, China; it has a contributing area ratio of
20:1 and depth of 15 cm. During the study period, we observed 28 large storm events, but only
5 of them caused overflow from the rain garden. The flow reduction rate for the overflow
events ranged from 77 to 94 %. The runoff coefficient from the contributing area (RC)was
reduced to less than 0.02 on annual basis, and 0.008 over the four years average. Field
observations also showed that infiltration rate remained stable during the operation period.
The predictions based on the future landuse and storm variability of the study area showed that
by converting a small fraction of the city land area into rain gardens, the negative hydrological
effect from expansion of impervious area can be reduced significantly. The challenge, how-
ever, lies in how to plan and build rain gardens as an integral part of the urban landscape.
Keywords Rain garden .Storm runoff .Design storm .Infiltration .Overflow.LID
Water Resour Manage (2016) 30:983–1000
DOI 10.1007/s11269-015-1206-5
*W. Lu o
luowan@yzu.edu.cn
1
State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area, Xi’an University of
Technology, Xi’an, China
2
Department of Agriculture and Water Resources Engineering, Yangzhou University, Yangzhou,
China
3
Department of Biological and Agricultural Engineering, North Carolina State University,
Raleigh, NC 27695-0001, USA
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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... and Agave spp.) as shown in Table 1 (Lizárraga-Mendiola et al., 2017). In Xi'an (China), the effect of 28 large storm events on an experimental rain garden has been studied out of which only 5 resulted in an overflow (Tang et al., 2016b). They recorded overflow reduction rates within the range of 77% and 94% and highlighted the ability of rain gardens to significantly reduce the negative hydrological effect of the built environment. ...
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Hydraulic performance of granular filter media and its evolution over time is a key design parameter for stormwater filtration and infiltration systems that are now widely used in management of polluted urban runoff. In fact, clogging of filter media is recognised as the main limiting factor of these stormwater treatment systems. This paper focuses on the effect of physical characteristics of filter media and flow-through rates on the clogging of stormwater filters. Five replicate experimental columns were constructed using zeolite, scoria, riversand and polymeric glass beads, and different flow-through rates were achieved using restricted outlets. The systems were dosed with semi-synthetic stormwater and the evolution of hydraulic performance and sediment removal rate was observed (for four filter media and across four flow rates) to investigate impacts of media type and flow rate. It was found that shape and smoothness of filter media grains had limited effect on clogging and sediment removal rate. All media except scoria clogged after similar volumes of stormwater but scoria-based filters were found to be highly variable in performance, most likely due to breakdown of its particles. Conversely, flow-through rate significantly affected clogging and sediment removal rate. For instance, in the case of zeolite filters, the systems with the lowest flow rate clogged after application of over 30 m of stormwater, while the unrestricted zeolite columns (with 200 times the flow rate) clogged after only 10 m of applied stormwater. At the same time, the zeolite filters with the lowest flow rate had an overall treatment efficiency of 88% compared with the unrestricted design’s efficiency of 59%. Further work is needed to analyse the influence of filter bed design, stormwater inflow characteristics and drying and wetting regimes on clogging and to understand the location of the clogged material in these filters.
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Flows into and out of two bioretention facilities constructed on the University of Maryland campus were monitored for nearly 2 years, covering 49 runoff events. The two parallel cells capture and treat stormwater runoff from a 0.24 ha section of an asphalt surface parking lot. The primary objective of this work was to quantify the reduction of hydrologic volume and flow peaks and delay in peak timing via bioretention. Overall, results indicate that bioretention can be effective for minimizing hydrologic impacts of development on surrounding water resources. Eighteen percent of the monitored events were small enough so that the bioretention media captured the entire inflow volume and no outflow was observed. Underdrain flow continued for many hours at very low flow rates. Mean peak reductions of 49 and 58% were noted for the two cells. Flow peaks were significantly delayed as well, usually by a factor of 2 or more. Using simple parameters to compare volume, peak flow, and peak delay to values expected for undeveloped lands, it was found that probabilities for bioretention Cell A to meet or exceed volume, peak flow, and peak delay hydrologic performance criteria were 55, 30, and 38%, respectively. The probabilities were 62, 42, and 31%, respectively, for Cell B.
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Three bioretention field sites in North Carolina were examined for pollutant removal abilities and hydrologic performance. The cells varied by fill media type or drainage configuration. The field studies confirmed high annual total nitrogen mass removal rates at two conventionally drained bioretention cells 40% reduction each. Nitrate-nitrogen mass removal rates varied between 75 and 13%, and calculated annual mass removal of zinc, copper, and lead from one Greensboro cell were 98, 99, and 81%, respectively. All high mass removal rates were due to a substantial decrease in outflow volume. The ratio of volume of water leaving the bioretention cell versus that which entered the cell varied from 0.07 summer to 0.54 winter. There was a significant p0.05 change in the ratio of outflow volume to inflow volume when comparing warm seasons to winter. Cells using a fill soil media with a lower phosphorus index P-index, Chapel Hill cell C1 and Greensboro cell G1, had much higher phosphorus removal than Greensboro cell G2, which used a high P-index fill media. Fill media selection is critical for total phosphorus removal, as fill media with a low P-index and relatively high CEC appear to remove phosphorus much more readily.
Urban stormwater treatment using bioretention
Article
Urban stormwater has negative environmental and ecological effects. Bioretention systems are starting to be used in efforts to mitigate these effects. A bioretention system receiving water from a light industrial catchment and a busy road was designed, built and monitored for changes in soil physics as well as hydrological and hydrochemical efficiency. The soils in the bioretention system were designed to have high metal removal potential and high permeability to compensate for undersized bioretention volume. The inflow hydrograph was a series of sharp peaks with little baseflow, typical of runoff from impervious surfaces. The bioretention system smoothed the hydrograph by reducing peak flow and volume for all 12 events monitored in detail. Overflow occurred in 10 events indicating the increased permeability did not fully compensate for the undersized volume. Runoff was heavily polluted with sediment and heavy metals, in particular zinc. The majority of the zinc, lead and Total Suspended Sediments were removed from the stormwater that flowed through the bioretention system, with TSS and total zinc concentrations reducing by orders of magnitude. Despite high removal efficiency, median concentrations of zinc exiting the bioretention system still exceeded ecosystem health guidelines and the bioretention system was both a source and sink of copper.
Fines Accumulation and Distribution in a Stormwater Rain Garden Nine Years Post Construction
Article
Storm water control measures (SCMs), also known as best management practices (BMPs), such as rain gardens, are designed to infiltrate storm-water runoff and reduce pollutant transport to surface waters. The life span of these SCMs may be limited depending on the composition of sediments in runoff water. Settling of fine sediments may clog soil pore spaces, reducing the infiltration capacity of the soil and reducing the potential benefits of this SCM. A study was conducted on a Villanova campus rain garden that accepts runoff from an adjacent parking lot to determine if there was a relationship between the accumulation of fine sediments over time and the infiltration capacity. The soil textural profile within the rain garden was characterized prior to SCM installation (2001), after installation, after five years, and after seven years of receiving storm-water runoff. Infiltration data were collected by the single-ring infiltrometer method in 2006 and 2009. Differences in soil texture were found between locations within the infiltration basin, and accumulation of fines smaller than 0.1 mm was observed at both locations sampled in 2009. Infiltration rates were significantly different between the two locations measured within the rain garden, but infiltration rates did not change significantly over time within those regions. This SCM was designed at a 10:1 watershed to SCM area ratio, which is twice what is recommended by the PA DEP BMP Manual. The data collected over the seven years since installation indicate that while fines have accumulated in the SCM there has been no significant change in infiltration potential.