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Increased precipitation, ageing infrastructure, and rising surface water levels have exacerbated stormwater issues in the city of Detroit, causing combined sewer overflows and basement flooding. Green stormwater infrastructure (GSI) is now a requirement of the city as part of its stormwater discharge permit to decrease stormwater system overflows. While GSI has been shown to improve water quality in combined sewer overflows, there has been widely-varying conclusions in flood mitigation potential. This study applied a calibrated EPA Stormwater Management Model (EPA SWMM) to investigate the potential flood mitigation benefits of GSI at a neighborhood scale in the city of Detroit. Results suggest the greatest flood mitigation occurs when locating larger scale GSI (i.e. bioretention basin, bioswale, green roof) in areas that are towards the upstream end of the storm sewer system. However, smaller-scale GSI systems (i.e. rain gardens) were also shown to be effective in flood mitigation in limited cases. [ABSTRACT FROM AUTHOR]

Comprehensive management of urban drainage network infrastructure is essential for sustaining the operation of these systems despite stresses from component deterioration, urban densification, and a predicted intensification of rainfall events. In this context, up-to-date and accurate urban drainage network data is key. However, such data is often absent, outdated, or incomplete. In this study, a new approach to localize manhole covers and storm drains, using deep learning to mine publicly available street-level images, is presented, tested, and assessed. Thus, the time-consuming and costly acquisition of the location of these system components can be avoided. The approach is evaluated using 5,000 high-resolution panoramas covering 500 km of public roads in Switzerland. The object detection approach proposed shows good performance and an improvement over state of the art image-based urban drainage infrastructure component detection. While the geographical localization of the detected objects still contains errors, the accuracy achieved is nevertheless sufficient for some applications, e.g. flood risk assessment. [ABSTRACT FROM AUTHOR]

Urban flood simulation often ignores or simplifies the function of underground gully systems due to data and computational limitations. To discover the influence of gullies on urban flooding, a novel approach is proposed in this study, by fully-coupling a 1D gully flow model (GFM), a 1D sewer flow model (SFM), and a 2D overland flow model (OFM) to simultaneously simulate the flow exchanges between surface, gullies and sewer pipes. This fully-coupled approach is compared with a simplified approach which directly introduces surface water into sewer pipes without being via gullies. The validation results show that the fully-coupled approach considerably reduces the underestimation of flood extent by 27% compared with the simplified approach. Without considering the capacity of lateral tubes between gullies and sewer pipes, the simplified approach over-drains the surface water into sewer pipes. The modelling of gully flow is crucial for correctly evaluating the efficiency of drainage systems. [ABSTRACT FROM AUTHOR]

A pervious concrete area (50 m2) was constructed for a dual purpose: stormwater management and bicycle parking. It consisted of two subareas (PCa and PCb) with dissimilar characteristics of pervious concrete mixes in strength, durability and permeability. To make the construction more eco-friendly and economical, coal fly ash was incorporated as a partial cement replacement by 21.4% in the PCa pervious concrete mix. The PCb was constructed with an industry proprietary pervious concrete mix. The subbase water storage can retain 4.1 m3 of the infiltrated stormwater before discharging excess water to a storm drain. The drainage water had an improved water quality in turbidity, organic carbon, phosphorus and fecal coliform concentrations. However, it had high pH and conductivity which might cause a negative impact on the environment. The constructed area has been in active use since its opening, accommodating ~30 bicycles at once on the safe and comfort pervious surface. [ABSTRACT FROM AUTHOR]

Swales are one type of sustainable drainage system (SuDS) which contribute to the management of water quality in receiving waterbodies. Using a semi-quantitative approach, an impact assessment procedure is applied to the residual water quality that is carried forward to surface waters and groundwaters following treatment within a swale. Both volumetric and pollutant distributions are considered as stormwater passes through the swale system. The pollutant pathways followed by TSS, nitrate, chloride, metals (Cd, Cu, Pb, Zn) and polyaromatic hydrocarbons (PAHs) are determined for a swale receiving highway runoff. For TSS, metals and PAHs between 20% and 29% of the total mean influent pollutant load is predicted to be directed to infiltration through the underlying soils compared to between 4% and 16% of chloride and nitrate. Although surface water impacts are deemed possible, the discharges of swales to groundwaters are assessed to represent a negligible impact for effectively maintained systems. [ABSTRACT FROM AUTHOR]

This paper presents a model (inspired by another model) to calculate water temperature in free-surface flow with two main innovations: the convective heat transfer occurs only at the wetted perimeter of pipes, and the model was integrated to commercial software used for hydraulic calculations in drainage systems. Given these innovations, we could reduce the number of modeling input data to calculate the temperature of water and soil in the radial and tangential directions along the pipes, with the advantages of using industry-standard software. To test the performance of the model, it was firstly calibrated in two sets of experiments (to calibrate the hydraulic and the thermal parameters separately), and benchmarked with a third controlled discharge against the case model. The results indicate that in unsteady-state situations the parsimonious model can be twice as accurate as the underlying model because the parsimonious model considers the hydraulic influence of sewer infrastructure. [ABSTRACT FROM AUTHOR]

Storm sewer systems (SSSs) are complex, with many hydraulic, mechanical and electrical components which may fail during natural extreme events, changing environmental conditions (including urban development), or simply due to poor maintenance. System complexity and management are important and still debated concepts within the framework of SSS risk analysis. A new probabilistic model for a conceptualized urban SSS, including a storage unit (SU) and a pumping station (PS), shows how single-component risk analysis can be extended to complex SSSs and demonstrates the combined effect of key design parameters (SU volume, detention time, prescribed outflow discharge) and management strategy on the overall SSS risk of failure. The risk of failure evaluated in a typical case study, demonstrates that economic restrictions leading to the loss of reliability of PS elements and the lack of redundant mechanical elements represent a major threat to SSSs and suggests a new risk-based definition of ’extended’ SU. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate small-scale infiltration losses of Portuguese cobblestone pavements. This type of pavement consists of rectangular hand-cut natural stones, mainly limestone, with different sizes and it is the most usual type of pavement for sidewalks and squares in Portuguese villages and cities. Portuguese cobblestone pavement can also be seen in several urban environments worldwide. A double-ring infiltrometer under constant and falling head was used for the field research work. Portuguese cobblestone pavements with small and coarse blocks were studied. The latter yield lower infiltration rates when compared to the former. The results show that, despite the block size, Portuguese cobblestone pavement contribute to reduce runoff, when compared with other impervious urban pavements. [ABSTRACT FROM AUTHOR]

Data for adjustment of weather radar rainfall estimations are mostly obtained from rain gauge observations. However, the density of rain gauges is often very low. Yet in many urban catchments, runoff sensors are typically available which can measure the rainfall indirectly. By utilising these sensors, it may be possible to improve the ground rainfall estimate, and thereby improve the quantitative precipitation estimation from weather radars for urban drainage applications. To test the hypothesis, this paper presents a rainfall measurement method based on flow rate measurements from well-defined urban surfaces. This principle was used to design a runoff measurement system in a parking structure in Aalborg, Denmark, where it was evaluated against rain gauges. The measurements show that runoff measurements from well-defined urban surfaces perform just as well as rain gauges. This opens up the possibility of improving the ground rainfall estimate by the use of flow rate measurements. [ABSTRACT FROM PUBLISHER]

At the building scale, green roof has demonstrated a positive impact on urban runoff (decrease in the peak discharge and runoff volume). This work aims to study if similar impacts can be observed at a basin scale. It is particularly focused on the possibility to solve some operational issues caused by storm water. For this purpose, a methodology has been proposed. It combines: a method to estimate the maximum roof area that can be covered by green roof, called green roofing potential, and an urban rainfall-runoff model able to simulate the hydrological behaviour of green roof. This methodology was applied to two urban catchments, one affected by flooding and the other one by combined sewage overflow. The results show that green roof can reduce the frequency and the magnitude of such problems depending on the covered roof surface. Combined with other infrastructures, they represent an interesting solution for urban water management. [ABSTRACT FROM AUTHOR]

The overall objective of this paper is to contribute to the standing debate concerning the advantages of separate sewer systems compared to traditional combined sewer systems. By a case study this investigation reveals that transformation of part of a town from being serviced with combined sewer systems to become serviced with separate sewer systems decreases the volumes of storm water and pollutants diverted to the waste water treatment plant and discharged as combined sewer overflow. This happens at the expense of an increase in volumes of storm water and pollutant loads diverted to local receiving waters when detention ponds are not built-in the new separate sewer systems. It is concluded that consequences can be fatal for receiving waters, if no retention of pollutants is integrated into the system. [ABSTRACT FROM AUTHOR]

This study conducted statistical analysis under both stationary and non-stationary climate using rainfall data measured in Seoul, South Korea. The 50 year annual maximum rainfall data were analysed with generalised extreme value distribution and Gumbel distribution. Possible rainfall changes were predicted with nonstationary forms of the two distributions, considering time variable location parameters. The current storm sewer design criteria were assessed by reflecting climate change implications and expected lifetime performance. Expected return periods were reduced to 4.67, 8.66, 19.16 and 23.53 years for the current 10 min - 5, 10, 30 and 50 years. The newly suggested design criteria of 5, 10, 30 and 50 yr return period storm events were 5.3, 12, 48 and 107 years for the 10 min duration for a 50 year lifetime expectancy. [ABSTRACT FROM AUTHOR]

Real Time Control (RTC) has become an accepted technique for improving the performance of Urban Drainage Systems (UDS) due to its flexibility and sustainability. Numerous implementations of RTC have been reported during the last decades. At the same time, guideline documents and state-of-the-art reports have been published. Whereas the general aspects and challenges of planning and installation of RTC systems are well covered, there is a lack of information about the adequate equipment for RTC of UDS. After identifying and briefly discussing the basic components of RTC systems for UDS, this paper describes the specific components in detail. This comprises the introduction of available technologies for sensors, actuators, controllers and telemetry systems in the context of RTC and the discussion of their potential and limitations. Lessons learned from the field operational experiences and future trends and challenges are identified. [ABSTRACT FROM PUBLISHER]

Permit regulations in the U.S. for Municipal Separate Storm Sewer Systems (MS4) require the MS4 to develop a program that detects and eliminates illicit discharges (e.g., improper wastewater connections) into the storm sewer system. Municipalities are interested in cost-effective methods to meet the permit requirements of this federal mandate. Our demonstration project with municipalities in Western New York State evaluated low cost options for illicit discharge trackdown. First, a visual reconnaissance was used to document flowing stormwater outfalls in dry weather. Subsequently, a sampling program was conducted, in combination with decision-making tools, to identify possible sources of illicit discharges. Colorimetric techniques were tested for a number of chemical parameters and the Coliscan Easygel® system was tested for E. coli analysis. Results from these various cost-effective analytical techniques were compared with analysis by standard methods. The E. coli test, in particular, had good precision and was useful in trackdown. [ABSTRACT FROM AUTHOR]

Storm sewer networks are usually designed under a certain predefined design storm. This paper proposes a general framework for a risk-based storm sewer network design, which is capable of taking future risk into account. In the framework, the flood risk evaluation is located within an optimisation loop. The flood risk is obtained by integrating the area under the probabilistic flood consequence curve, which is identified by simulations of sewer system performance under several design storms. The genetic algorithm is adapted for this specific optimisation problem in order to make the procedure computationally efficient. The framework is applied to the designs of a synthetic network and a real-world network. The results show that the general framework is able to identify the network design balancing the construction cost and flood risk. [ABSTRACT FROM AUTHOR]

Wastewater and stormwater collection and conveyance systems are undergoing aging and deterioration, leaving cities vulnerable to their ill-effects, e.g. collapse and flooding. To avoid such problems, utilities began implementing some sort of urban drainage infrastructure asset management systems. One of the key components of these systems is the ability to predict the infrastructure's future performance. This paper discusses the different statistical models used in predicting the structural deterioration of urban drainage pipes. The concepts behind the models, along with their data requirements and applications in infrastructure asset management, are presented. Finally, a discussion is also made on the issues and challenges related to the developments of these models. [ABSTRACT FROM AUTHOR]

Total suspended solids as a measure of suspended particles in urban stormwater has limitations and the alternative suspended sediment concentration method was adapted to determine non-coarse particle (NCP) concentration, defined as particles smaller than 500 μm. NCP was partitioned into the following classes: very fine particles (<8 μm, VFP), fine particles (8-63 μm, FP) and medium particles (63-500 μm, MP). A site mean concentration approach was adopted to differentiate the suspended particle characteristics between three impervious surfaces (roof, road and car park) using runoff data collected for 35 storms. Runoff particle size distribution (PSD) of all surfaces was dominated by particles less than 63 μm. A weak trend of relatively constant VFP concentration was present in the road runoff data. Roof runoff PSD became finer as NCP concentration increased and, overall, the PSD of car park runoff was coarser compared to road and roof runoff. These findings have runoff treatment implications as settling processes are influenced by particle size. [ABSTRACT FROM AUTHOR]