Special Issue "Rainwater Management in Urban Areas"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Urban Water Management".

Deadline for manuscript submissions: closed (15 December 2020).

Special Issue Editor

Prof. Dr. Brigitte Helmreich
E-Mail Website
Guest Editor
Urban Water Systems Engineering, Department of Civil, Geo and Environmental Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany
Interests: monitoring of stormwater runoff pollutants (organic and inorganic); development and evaluation of treatment systems for stormwater runoff of traffic areas and roofs; rainwater harvesting systems; stormwater management
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Special Issue Information

Dear Colleagues,

Rising levels of impervious surfaces as well as new circumstances such as heavy rain events or dry weather periods provide us with new challenges for sustainable stormwater management in urban areas. Best management practices are widely applied to reduce the quantity and to improve the quality of stormwater runoff. Especially, a variety of decentralized treatment facilities have been developed as a supplement to conventional sewer systems. Currently, research is ongoing on the performance and operation of such facilities. Additionally, the sustainability regarding natural water balance and the impact on the environment are under consideration.

This Special Issue of Water will focus on the sustainability and environmental effects of stormwater management in urban areas (quantity and quality). The Special Issue will consider:

  • Monitoring of stormwater runoff quality including new parameters;
  • Hydrological models for stormwater runoff in urban catchments;
  • Build-up and wash-off models for pollutants from impervious surfaces;
  • Lab-scale, pilot-scale, and long-term experience with decentralized treatment systems;
  • Testing procedures and protocols for stormwater treatment systems;
  • Legal and practical opportunities to avoid or minimize the risks of groundwater and surface water contamination;
  • Impact of decentralized stormwater management on existing sewer systems;
  • Testing procedures and protocols for stormwater treatment systems.

Prof. Dr. Brigitte Helmreich
Guest Editor

Manuscript Submission Information

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Keywords

  • urban stormwater runoff
  • runoff pollution
  • decentralized treatment
  • centralized treatment
  • stormwater runoff models
  • build-up and wash-off models
  • environmental risk assessment

Published Papers (11 papers)

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Editorial

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Editorial
Rainwater Management in Urban Areas
Water 2021, 13(8), 1096; https://doi.org/10.3390/w13081096 - 16 Apr 2021
Viewed by 457
Abstract
Rising levels of impervious surfaces in densely populated cities and climate change-related weather extremes such as heavy rain events or long dry weather periods provide us with new challenges for sustainable stormwater management in urban areas. The Special Issue consists of nine articles [...] Read more.
Rising levels of impervious surfaces in densely populated cities and climate change-related weather extremes such as heavy rain events or long dry weather periods provide us with new challenges for sustainable stormwater management in urban areas. The Special Issue consists of nine articles and a review and focuses on a range of relevant issues: different aspects and findings of stormwater runoff quantity and quality, including strategies and techniques to mitigate the negative effects of such climate change impacts hydraulically, as well as lab-scale and long-term experience with pollutants from urban runoff and the efficiency of stormwater quality improvement devices (SQIDs) in removing them. Testing procedures and protocols for SQIDs are also considered. One paper analyses the clogging of porous media in the use of stormwater for managed aquifer recharge. The Special Issue demonstrates the importance and timeliness of the topic of sustainable rainwater management, especially with regard to growing cities and the challenges posed by climate change. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)

Research

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Article
Assessing the TSS Removal Efficiency of Decentralized Stormwater Treatment Systems by Long-Term In-Situ Monitoring
Water 2021, 13(7), 908; https://doi.org/10.3390/w13070908 - 26 Mar 2021
Cited by 1 | Viewed by 607
Abstract
Decentralized treatment of stormwater runoff from heavily polluted surface can be a good solution for effective source control. Decentralized stormwater treatment systems (DS) and test procedures to monitor their performance, have been developed in recent years. At present in Germany, only lab-based tests [...] Read more.
Decentralized treatment of stormwater runoff from heavily polluted surface can be a good solution for effective source control. Decentralized stormwater treatment systems (DS) and test procedures to monitor their performance, have been developed in recent years. At present in Germany, only lab-based tests are officially established to determine the removal efficiency of Total Suspended Solids (TSS), and in situ monitoring is still lacking. Furthermore, the fine fraction of TSS with particle sizes less than 63 µm (TSS63) have been established as a new design parameter in Germany, because of their substitute characteristics of adsorbing pollutant substances. For research and evaluation purposes continuous data of urban stormwater runoff quantity and quality at the in- and outflow of two different DS at two different sites were collected. Turbidity is used as a surrogate for TSS. Continuous turbidity data and time proportional sampling served to obtain (i) regression coefficients and (ii) to determine the TSS removal efficiency of DS. For a wide range of events the total removal efficiency of DS1 was 29% for TSS and 19% for TSS63 and for DS2 19% for TSS and 16% for TSS63. An event-based data analysis revealed a high variability of the efficiencies and its uncertainties. Moreover, outwash of still suspended or remobilization of already deposited material was observed at individual events. At both sites TSS63 dominates urban stormwater runoff as indicated by the mean ratios of TSS63 to TSS of 0.78 at the inflows and 0.89 at the outflows of both DS. A significant shift of TSS63 ratio from inflow to outflow demonstrates that TSS63 particles were removed less efficiently than coarser particles by DS1, for DS2 data was too heterogeny. It clarifies that common sedimentation methods can only contribute to a small extent to the reduction of solid emissions if the stormwater runoff contains mainly fine-particle solids. The findings suggest that treatment of urban stormwater runoff with high TSS63 pollution requires additional techniques such as a proper filtering to retain fine particles more effective. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Development of a New Testing Approach for Decentralised Technical Sustainable Drainage Systems
Water 2021, 13(5), 722; https://doi.org/10.3390/w13050722 - 06 Mar 2021
Cited by 1 | Viewed by 742
Abstract
A part of the sustainable drainage systems (SuDS) are used to treat stormwater and must be tested for their hydraulic performance and the removal efficiency to assess serviceability and retention of the pollutants efficacy for in situ use. Current test procedures provide a [...] Read more.
A part of the sustainable drainage systems (SuDS) are used to treat stormwater and must be tested for their hydraulic performance and the removal efficiency to assess serviceability and retention of the pollutants efficacy for in situ use. Current test procedures provide a good basis for laboratory testing SuDS on the test stand. However, the evaluation is not sufficiently representative to compare different SuDS with each other or for in situ use. The individual steps and specifications of an applied test procedure in Germany were considered and evaluation and optimizations for the test substance and sampling methodology of SuDS on the test stand were proposed. A comparison of the particle size distribution of the test substance Millisil W4 currently in use and total suspended solids of real road runoff was made, which showed that the presented test substance of real road-deposited sediments (RDS) provides a better reference for the test conditions and they could be the basis for more representative test methods. A particle size distribution was proposed for this new test substance. Furthermore, two methods of sampling were compared, which showed that a full flow sampling is preferable to a discrete sample. At the same time, it was shown that a separation limit of 20 µm is sufficient for the determination of TSS63. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Adsorption of Metals to Particles in Urban Stormwater Runoff—Does Size Really Matter?
Water 2021, 13(3), 309; https://doi.org/10.3390/w13030309 - 27 Jan 2021
Cited by 2 | Viewed by 492
Abstract
The parameter total suspended solids (TSS) is often used to evaluate the need for stormwater treatment or to assess the effectiveness of treatment measures. The purpose of this study is to analyze the value and the limitations of this approach using metals as [...] Read more.
The parameter total suspended solids (TSS) is often used to evaluate the need for stormwater treatment or to assess the effectiveness of treatment measures. The purpose of this study is to analyze the value and the limitations of this approach using metals as an example. They are of major concern due to their accumulating effects in the environment. Data of a monitoring campaign at a stormwater treatment facility is evaluated. TSS, organic matter and the associated metals (Cr, Cu, Zn, Cd, and Pb) were analyzed in four different particle size fractions (<63 µm, 63–125 µm, 125–250 µm, and 250–2000 µm). While the highest event meant concentrations for all metals were found in the smallest fraction, a rather uniform particulate bound metal concentration (mass of metal per mass of particulate matter) over the first three particle size fractions was detected. Total metal loads correlated well with TSS even better with TSS < 63 µm. However, the removal efficiency in terms of the reduction of the total metal load was not reflected sufficiently by the TSS or TSS < 63 µm removal efficiency. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Laws and Mechanism of the Fe (III) Clogging of Porous Media in Managed Aquifer Recharge
Water 2021, 13(3), 284; https://doi.org/10.3390/w13030284 - 25 Jan 2021
Cited by 1 | Viewed by 417
Abstract
The use of stormwater for managed aquifer recharge (MAR) has become one of the most important ways to deal with water shortages and the corresponding environmental geological problems, especially in the north of China. The Fe (III) clogging of porous media is a [...] Read more.
The use of stormwater for managed aquifer recharge (MAR) has become one of the most important ways to deal with water shortages and the corresponding environmental geological problems, especially in the north of China. The Fe (III) clogging of porous media is a common and significant problem that influences the effect of the infiltration rate. This paper focuses on the migration characteristics and clogging mechanisms of iron hydroxides in sand columns. The results indicate that the permeability of porous media significantly decreased at the inlet of the fine sand column and inside the coarse sand column. We demonstrated that, when the Fe (III) concentration was higher, a smaller infiltration medium size was produced more rapidly, and there was more significant clogging. More than 80% of the injected Fe (III) remained in the sand column, and more than 50% was retained within 1 cm of the column inlet. The mass retention increased with the decrease in the size of the infiltration medium particles and with the increase in the injected Fe (III) concentration. The main material that caused Fe (III) clogging was iron hydroxide colloids, which were in the form of a granular or flocculent membrane coating the quartz sand. The mechanisms of clogging and retention were blocking filtration and deep bed filtration, adsorption, and deposition, which were strongly affected by the coagulation of Fe (III) colloidal particles. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
SWMM-UrbanEVA: A Model for the Evapotranspiration of Urban Vegetation
Water 2021, 13(2), 243; https://doi.org/10.3390/w13020243 - 19 Jan 2021
Cited by 1 | Viewed by 654
Abstract
Urban hydrology has so far lacked a suitable model for a precise long-term determination of evapotranspiration (ET) addressing shading and vegetation-specific dynamics. The proposed model “SWMM-UrbanEVA” is fully integrated into US EPA’s Stormwater Management Model (SWMM) and consists of two submodules. Submodule 1, [...] Read more.
Urban hydrology has so far lacked a suitable model for a precise long-term determination of evapotranspiration (ET) addressing shading and vegetation-specific dynamics. The proposed model “SWMM-UrbanEVA” is fully integrated into US EPA’s Stormwater Management Model (SWMM) and consists of two submodules. Submodule 1, “Shading”, considers the reduction in potential ET due to shading effects. Local variabilities of shading impacts can be addressed for both pervious and impervious catchments. Submodule 2, “Evapotranspiration”, allows the spatio-temporal differentiated ET simulation of vegetation and maps dependencies on vegetation, soil, and moisture conditions which are necessary for realistically modeling vegetation’s water balance. The model is tested for parameter sensitivities, validity, and plausibility of model behaviour and shows good model performance for both submodules. Depending on location and vegetation, remarkable improvements in total volume errors Vol (from Vol = 0.59 to −0.04% for coniferous) and modeling long-term dynamics, measured by the Nash–Sutcliffe model efficiency (NSE) (from NSE = 0.47 to 0.87 for coniferous) can be observed. The most sensitive model inputs to total ET are the shading factor KS and the crop factor KC. Both must be derived very carefully to minimize volume errors. Another focus must be set on the soil parameters since they define the soil volume available for ET. Process-oriented differentiation between ET fluxes interception evaporation, transpiration, and soil evaporation, using the leaf area index, behaves realistically but shows a lack in volume errors. Further investigations on process dynamics, validation, and parametrization are recommended. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Settling of Road-Deposited Sediment: Influence of Particle Density, Shape, Low Temperatures, and Deicing Salt
Water 2020, 12(11), 3126; https://doi.org/10.3390/w12113126 - 07 Nov 2020
Cited by 5 | Viewed by 597
Abstract
Separation of particulate matter (PM) is the most important process to achieve a reduction of contaminants present in road runoff. To further improve knowledge about influencing factors on the settling of road-deposited sediment (RDS), samples from three sites were collected. Since particle size [...] Read more.
Separation of particulate matter (PM) is the most important process to achieve a reduction of contaminants present in road runoff. To further improve knowledge about influencing factors on the settling of road-deposited sediment (RDS), samples from three sites were collected. Since particle size distribution (PSD) has the strongest effect on settling, the samples were sieved to achieve comparable PSDs so that the effects of particle density, shape, fluid temperature, and deicing salt concentration on settling could be assessed using settling experiments. Based on the experimental data, a previously proposed model that describes the settling of PM was further developed and validated. In addition, RDS samples were compared to a standard mineral material, which is currently in use to evaluate treatment efficiency of stormwater quality improvement devices. The main finding was that besides PSD, particle density is the most important influencing factor. Particle shape was thoroughly described but showed no significant improvement of the prediction of the settled mass. Temperature showed an effect on PM settling; deicing salts were negligible. The proposed models can sufficiently predict the settling of RDS in settling column experiments under varying boundary conditions and are easily applicable. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Pollutant Concentration Patterns of In-Stream Urban Stormwater Runoff
Water 2020, 12(9), 2534; https://doi.org/10.3390/w12092534 - 11 Sep 2020
Cited by 1 | Viewed by 564
Abstract
Although a number of studies have investigated pollutant transport patterns in urban watersheds, these studies have focused primarily on the upland landscape as the point of interest (i.e., prior to stormwater entering an open stream channel). However, it is likely that in-stream processes [...] Read more.
Although a number of studies have investigated pollutant transport patterns in urban watersheds, these studies have focused primarily on the upland landscape as the point of interest (i.e., prior to stormwater entering an open stream channel). However, it is likely that in-stream processes will influence pollutant transport when the system is viewed at a larger scale. One initial investigation that can be performed to characterize transport dynamics in urban runoff is determining a pollutant’s temporal distribution. By borrowing from urban stormwater literature, the propensity of a pollutant within a system to be more heavily transported in the initial portion of the storm can be quantified (i.e., the “first flush”). Although uncommon for use in stream science, this methodology allows direct comparison of results to previous studies on smaller urban upland catchments. Multiple methods have been proposed to investigate the first flush effect, two of which are applied in this study to two streams in Knoxville, TN, USA. The strength of the first flush was generally corroborated by the two unique methods, a new finding that allows a more robust determination of first flush presence for a given pollutant. Further, an “end flush” was observed and quantified for nutrients and microbes in one stream, a novel outcome that shows how the newer methodology that was employed can provide greater insight into transport processes and pollutant sources. Explanatory variables for changes in each pollutant’s inter-event first flush strength differed, but notable relationships included the influence of flow rate on microbes and influence of rainfall on Cu2+. The results appear to support the hypothesis that in-stream processes, such as resuspension, may influence pollutant transport in urban watersheds, pointing toward the need to consider in-stream processes in models developed to predict urban watershed pollutant export. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Modeling Green Roof Potential to Mitigate Urban Flooding in a Chinese City
Water 2020, 12(8), 2082; https://doi.org/10.3390/w12082082 - 22 Jul 2020
Cited by 4 | Viewed by 799
Abstract
The Middle and Lower Reaches of the Yangtze River (MLRYR) region, which has humid subtropical climate conditions and unique plum rain season, is characterized by a simultaneous high-frequency urban flooding and reduction in groundwater levels. Retrofitting the existing buildings into green roofs is [...] Read more.
The Middle and Lower Reaches of the Yangtze River (MLRYR) region, which has humid subtropical climate conditions and unique plum rain season, is characterized by a simultaneous high-frequency urban flooding and reduction in groundwater levels. Retrofitting the existing buildings into green roofs is a promising approach to combat urban flooding, especially for a densely developed city. Here, the application potential of the Green Roof System (GRS) and the Improved Green Roof System (IGRS) designed to divert overflowing water from green roofs to recharge groundwater were analyzed in a densely developed city, Nanchang, China. For the first time, the influence of GRS on the hydraulic condition of Combined Sewage System/Storm Water System (CSS/SWS) is analyzed, which is a direct reflection of the effect of GRS on alleviating urban flooding. The simulation results show that GRS can retain about 41–75% of precipitation in a 2-hour timescale and the flooding volumes in the GRS/IGRS region are 82% and 28% less than those of the Traditional Roof System (TRS) in 10- and 100-yr precipitation events, respectively. In the continuous simulations, GRS also enhances Evapotranspiration (ET), which accounts for 39% of annual precipitation, so that reduces the cumulative surface runoff. Considering the IGRS can provide more hydrological benefits than the GRS under the same climate conditions, we may conclude that the widespread implementation of both the GRS and the IGRS in Nanchang and other densely developed cities in the MLRYR region could significantly reduce surface and peak runoff rates. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Article
Effect of Urban Stormwater Road Runoff of Different Land Use Types on an Urban River in Shenzhen, China
Water 2019, 11(12), 2545; https://doi.org/10.3390/w11122545 - 02 Dec 2019
Cited by 9 | Viewed by 1039
Abstract
Urban storm runoff is a major source of pollutants in receiving water bodies. To assess the impact of urban stormwater runoff on an urban river, the runoff process of total suspended solids (TSS), chemical oxygen demand (COD), ammonium (NH4), and total [...] Read more.
Urban storm runoff is a major source of pollutants in receiving water bodies. To assess the impact of urban stormwater runoff on an urban river, the runoff process of total suspended solids (TSS), chemical oxygen demand (COD), ammonium (NH4), and total phosphorus (TP) were investigated on road surfaces classified as arterial road (AR), residential area (RA), and industrial area (IA) in the Pingshan River (PSR) watershed in Shenzhen, China. Event mean concentration (EMC) was calculated to analyze the water quality of road runoff, and the dimensionless M(V) cumulative curves were used to estimate the course of decreasing concentration of runoff pollutants during each rainfall event. Multicriteria decision making methods (PROMETHEE-GAIA) were used to identify the linkage between runoff pollutants, land use types, and rainfall intensity. The EMCs of COD and TP in runoff exceeded the class IV level of the water quality standard for surface water (China). RA was a major potential source for NH4, COD, and TP in the river. Controlling the first flush is critical to decrease the effect of road runoff on receiving water bodies, as most runoff pollutants in AR, RA, and IA had a first flush effect during heavy rainfall. The specific management measure for runoff pollution varied with land use type. Reducing road TSS concentrations was effective for controlling runoff pollution in AR and RA because NH4, TP, and COD attached to particulate matter. In IA, the collection and reuse of stormwater in the initial rainfall period were effective for reducing the effect of soluble pollutants in runoff on receiving water bodies. This study provides new information for managing urban road stormwater runoff in different land use types. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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Review

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Review
Urban Flooding Mitigation Techniques: A Systematic Review and Future Studies
Water 2020, 12(12), 3579; https://doi.org/10.3390/w12123579 - 20 Dec 2020
Cited by 2 | Viewed by 924
Abstract
Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the [...] Read more.
Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the amounts of runoff offsite. Although projects, such as low-impact development and water-sensitive urban design, have been proposed to retain, detain, infiltrate, harvest, evaporate, transpire, or re-use rainwater on-site, urban flooding is still a serious, unresolved problem. This review sequentially discusses runoff reduction facilities installed above the ground, at the ground surface, and underground. Mainstream techniques include green roofs, non-vegetated roofs, permeable pavements, water-retaining pavements, infiltration trenches, trees, rainwater harvest, rain garden, vegetated filter strip, swale, and soakaways. While these techniques function differently, they share a common characteristic; that is, they can effectively reduce runoff for small rainfalls but lead to overflow in the case of heavy rainfalls. In addition, most of these techniques require sizable land areas for construction. The end of this review highlights the necessity of developing novel, discharge-controllable facilities that can attenuate the peak flow of urban runoff by extending the duration of the runoff discharge. Full article
(This article belongs to the Special Issue Rainwater Management in Urban Areas)
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