EPA Storm Water Management Model Research Articles

Assessing the impacts of urbanization and climate change on urban drainage system

AbstractUrban flooding is one of the significant issues that many cities are dealing with to ensure sustainable development. Upgrading the drainage systems is a standard measure that engineers have often used to reduce the risk of flooding. Because of climate change and urbanization, stormwater management systems may be inadequate to convey generated overflow in their catchment, which results in severe flooding in many cities worldwide. This research investigates climate change and urbanization's influence on urban flooding by simulating the EPA Stormwater Management Model for drainage systems in an urban catchment in An Ha, Tam Ky, Quang Nam. The results showed that urbanization shortens the initial abstraction ability while climate change increases extreme rainfall and water levels of receiving sources. Additionally, the impacts are even more substantial when the high urbanization rate increases by more than 70%, together with climate change.

Modeling flow of the major canals of Sylhet city using the EPA SWMM runoff model

Abstract Geographically, local canals in Sylhet city, Bangladesh, mostly transport the rainwater to the Surma River as the city lacks typical drainage infrastructure for runoff control. Hence, proper hydraulic and hydrologic models are required to assess the current potential of these canals to withstand significant runoff and enhance the protection of flood problems during a severe storm. In this study, Malni Chara and Goali Chara sub-systems of Sylhet city's major drainage networks were calibrated and verified using the EPA Storm Water Management Model (SWMM), respectively, using the hydrological data from 2016 to 2019 and the meteorological data from 1975 to 2019. The models were suitable for measuring the runoff quantity since the simulated results matched the observed data well. For the Malni Chara sub-system, R2 of 0.94, Nash–Sutcliffe efficiency (NSE) of 0.92, d of 0.97, percent bias (PBIAS) (%) of 2.96%, and RMSE standard deviation ratio (RSR) of 0.05 have been found and for the Goali Chara sub-system, R2 of 0.96, NSE of 0.90, d of 0.93, PBIAS (%) of 1.54%, and RSR of 0.08 have been found.

Inconsistent using FLOOD and Flooding Development of EPA SWMM for Assessing Flood Occurrences in Vulnerable Urban Watershed Considering Extreme Rainfall Events

Urban flood, commonly known as urban water congestion, is a type of water hazard that poses significant challenges for urban residents and water management experts. Chittagong, an essential economic hub in Bangladesh, renowned for its role as a port city, comprises a diverse range of land use, including residential, industrial, and commercial sectors. The Chaktai canal, an important element of Chittagong drainage system, is connected to the Karnaphuli river, playing a vital role in managing drainage by handling a substantial portion of the city water. Therefore, this research evaluated the operational efficiency of a specific drainage network under the influence of altered rainfall events using the Storm Water Management Model (SWMM). Using ArcGIS 10.4, the land use pattern of the area was researched, incorporating data from field surveys and secondary sources. SWMM 5.1 integrated watershed data, and further simulation was carried out to estimate runoff in various sub-catchments and drainage network limitations during heavy rain. During the intense monsoon period, the tool determined the average runoff depth, considering backwater effects and robust tidal surges, resulting in a depth of 3.3m compared to 2.6m in the dry season. This research evaluated the influence of impervious land use changes on urban drainage systems. While meteorological factors alone render drainage network sufficient in dry periods, the outfall shows vulnerability during the rainy season, with an allowance of only 0.7m, jeopardizing the catchment through flood. It contributed a schematic sub-catchment representation, emphasizing that flood events depend on volume runoff and peak flow in urban drainage system. SWMM model was used to illustrate the catchment surface runoff and interconnected node depths via conduits, as well as the current catchment scenario comprehensively.

Retention Pond Planning for Flood Management Using Epa SWMM in Sayung Village Demak Regency

The area of Sayung Village, Sayung District, and Demak Regency is an area that is often hit by annual floods. According to the Sayung Village Government, floods in 2019 resulted in 5,884 residents of Sayung Village being displaced and 1,471 houses being flooded. The area of submerged rice fields is 300 hectares, with the number of farmers who failed to harvest reaching 436. Comprehensive handling is needed to deal with the flood. For flood management, a simulation of a flood management system was made with EPA SWMM (Environmental Protection Agency Storm Water Management Model) software. The selection of handling concepts is obtained through re-simulation of the capacity of drainage channels in order to accommodate planned discharge. To be able to perform simulations, hydrological data and measurements of existing channels are needed. Flood discharge obtained from the calculation results is Q2 of 110.1 m3 per second, Q5 of 134.9 m3 per second, and Q10 of 147.8 m3 per second. The handling concept obtained from this study is the creation of retention ponds in Dukuh Sayung Kidul and Dukuh Sayung Wetan.

Evaluating the Capacity of Existing Stormwater Drainage System in Kapan, Kathmandu via SWMM Mode

Overflowing drainage systems in the Nepalese cities are the most significant issue due to unplanned urban expansion and inadequate drainage networks. As the city's drainage networks are not designed to handle the extra runoff from catastrophic flooding incidents, flash floods typically occur during short-duration, and high-intensity rainstorm storms frequently. In the vicinity of Kapan, Kathmandu, and many other Nepalese cities, particularly during the rainy season, roads are seen changing into the streams. This study employs a hydrological analysis model to examine the storm water drainage system existing currently in the Kapan area. Being the EPA Storm Water Management Model (SWMM) physically based, deterministic type that simulates the inflows, outflows, and storages of water within a sub-catchment efficiently, it is chosen here mainly to model the catchments specifically. Though it has not been employed frequently in the context of Nepal, despite its popularity in the industrialized countries such as United States of America for the proper management of the storm water, the SWMM is particularly employed here to model the catchments due to its publicly available, easy to obtain, simple data input parameters, and simple processing steps in compared to other relatively more expensive yet sophisticated models. The catchment's overall area of 360.57 hectares was at first separated into the 86 sub catchments using the SWMM based on its surface elevation and existing drainage network, and the attributes of each sub-catchment were then assigned accordingly. After the proper identification of the sub-catchments, the runoff from the relevant sub-catchments was routed to the respective nodes, and finally to the outlet via conduits. In the current study, the drain system (Combined Sewer line) is given along the center of the road network. The storm network are represented by junctions, conduits, and outfalls. The longitudinal and velocity profiles of the drain were obtained. The critical runoff and capacity of existing drains were determined, as well as their validation with discharge derived using the rational technique. With the runoff generated during peak rainfall 45.08 mm/hr., the Kapan area's existing drainage system was found to be insufficient. This study suggests that the SWMM would be the most effective model to be employed for predicting the sudden surface runoff and for prior managing of the storm water, particularly in Kathmandu and other vulnerable parts of main cities in Nepal, where overflow has caused serious problems during rainfall.

Water Sensitive Urban Design (WSUD) Spatial Prioritisation through Global Sensitivity Analysis for Effective Urban Pluvial Flood Mitigation

Water Sensitive Urban Design (WSUD) has attracted growing attention as a sustainable approach for mitigating pluvial flooding (also known as flash flooding), which is expected to increase in frequency and intensity under the impacts of climate change and urbanisation. However, spatial planning of WSUD is not an easy task, not only due to the complex urban environment, but also the fact that not all locations in the catchment are equally effective for flood mitigation. In this study, we developed a new WSUD spatial prioritisation framework that applies global sensitivity analysis (GSA) to identify priority subcatchments where WSUD implementation will be most effective for flood mitigation. For the first time, the complex impact of WSUD locations on catchment flood volume can be assessed, and the GSA in hydrological modelling is adopted for applications in WSUD spatial planning. The framework uses a spatial WSUD planning model, the Urban Biophysical Environments and Technologies Simulator (UrbanBEATS), to generate a grid-based spatial representation of catchment, and an urban drainage model, the U.S. EPA Storm Water Management Model (SWMM), to simulate catchment flooding. The effective imperviousness of all subcatchments was varied simultaneously in the GSA to mimic the effect of WSUD implementation and future developments. Priority subcatchments were identified based on their influence on catchment flooding computed through the GSA. The method was tested for an urbanised catchment in Sydney, Australia. We found that high priority subcatchments were clustering in the upstream and midstream of the main drainage network, with a few distributed close to the catchment outlets. Rainfall frequency, subcatchment characteristics, and pipe network configuration were found to be important factors determining the influence of changes in different subcatchments on catchment flooding. The effectiveness of the framework in identifying influential subcatchments was validated by comparing the effect of removing 6% of the Sydney catchment's effective impervious area under four WSUD spatial distribution scenarios. Our results showed that WSUD implementation in high priority subcatchments consistently achieved the largest flood volume reduction (3.5-31.3% for 1% AEP to 50% AEP storms), followed by medium priority subcatchments (3.1-21.3%) and catchment-wide implementation (2.9-22.1%) under most design storms. Overall, we have demonstrated that the proposed method can be useful for maximising WSUD flood mitigation potential through identifying and targeting the most effective locations.

Analysis of flood control in Lambidaro sub-watershed using EPA SWMM

In the Lambidaro sub-watershed, precisely on Jalan Colonel Sulaiman Amin, the problem of flooding continues, especially when it rains. The occurrence of flooding around the canal along the Colonel Sulaiman Amin road drainage is caused by several factors, one of which is the capacity of the reservoir which is not able to control the flood discharge optimally so that water cannot overflow into the canal. and eventually caused flooding in the surrounding area. This study aims to determine whether the drainage capacity is still able to drain surface runoff water or not and determine alternative flood control solutions for Colonel Sulaiman Amin Street. The method used is the EPA Model SWMM (Environmental Protection Agency Storm Water Management Model). From this study, the simulation results obtained from EPA SWMM showed alternative solutions offered such as the use of flood pumps, retention ponds, and optimization of drainage, the most effective solution of the six flood mitigation experiments was channel optimization in the form of changing the shape and size of the channel 7 to a square channel with a width of 1 .5 meters. This alternative is 5.26% more effective with an effective percentage of 85.538% and can drain 36.36% more water flow than drainage with a widening of 1.1 meters.

Modeling bioretention hydrology: Quantifying the performance of DRAINMOD-Urban and the SWMM LID module

• Bioretention volume and hydrograph performance of two calibrated models was compared. • SWMM produced good predicted volumes and outflow hydrographs even when uncalibrated. • DRAINMOD-Urban better represented measured drainage hydrograph shape than SWMM. • Hydrograph-calibration was closest to measured hydrographs and volumes in DRAINMOD-Urban. • In SWMM, the calibration method optimized measured hydrographs or volumes but not both. Bioretention systems have become a leading infiltration-based Low Impact Development (LID) practice to reduce urban stormwater runoff volumes and peak flows. Although these systems have performed well in many site-scale field studies, modeling of bioretention systems has received less attention. Additional studies are needed which calibrate various models to field measurements to investigate and optimize the performance of individual LID practices and effectively scale local interventions to the watershed. DRAINMOD-Urban has been successfully applied to bioretention at the site-scale due to its advanced soil–water accounting using the soil–water characteristic curve and its ability to explicitly model underdrains and internal water storage (IWS) zones. At the same time, the U.S. EPA Stormwater Management Model (SWMM) has become one of the most widely used urban drainage models. The latest version, SWMM5, included dedicated LID modules including a routine for bioretention modeling. In this study, DRAINMOD-Urban and the SWMM LID module were compared through detailed analysis of the internal processes of each model as well as through model calibration and output investigation. The objective was to identify the strengths and weaknesses of each model and compare the performance of both models to a single bioretention cell. Both SWMM and DRAINMOD-Urban were evaluated in calibrated and uncalibrated scenarios since urban drainage models often remain uncalibrated for planning scenario analysis. Following calibration, DRAINMOD-Urban was superior for replicating drainage hydrographs (NSE = 0.60) while SWMM produced better overflow hydrographs (NSE = 0.57). Specifically, SWMM often output a maximum drainage rate that caused rectangular drainage hydrographs, but DRAINMOD-Urban was better able to match the shape of measured drainage hydrographs. While the DRAINMOD-Urban model output was in good agreement with measured drainage and overflow event volumes when calibrated (drainage NSE = 0.83, overflow NSE = 0.57–0.66), SWMM was closer to measured volumes even when uncalibrated (drainage NSE = 0.70–0.93, overflow NSE = 0.59–0.81). This study improved existing knowledge of the SWMM LID module by calibrating to field-collected data from a single bioretention cell for the first time in literature. Furthermore, the results of this study indicate an opportunity for model coupling that could combine the strengths and weaknesses of each model and improve bioretention cell modeling.

Numerical Comparison of the Hydrological Response of Different Permeable Pavements in Urban Area

Floods are becoming more frequent, especially in urban environments where most of the surface is waterproofed. Permeable pavement (PP) can be applied as low impact development (LID) systems for runoff mitigation in urban areas. Their effectiveness can be assessed, case by case, by numerical simulations. In this study, the effectiveness of mitigating runoff of different permeable pavements has been evaluated. In particular, porous asphalt (PA), pervious concrete (PC), permeable interlocking concrete pavement (PICP) and grid pavement (GP) have been investigated using EPA Storm Water Management Model (SWMM) software. To this aim, a car parking area located in the University Campus of Palermo (Italy) has been taken as a case study, considering several scenarios, each having a different percentage and planimetric layout of a PP type combined with an impermeable pavement. All the scenarios were tested assuming four synthetic rainfall events, referring to return periods of 5, 10, 50 and 100 years, and a real high return period event that occurred in Palermo in 2020. The results showed that amongst the different PPs considered, only the PA, bounded at the bottom by an impermeable layer, was practically ineffective. The other three PPs, proved to be effective in a noticeable way and furthermore for each scenario studied, they proved to bear almost the same mitigated runoff. The results proved appreciable differences in runoff as a function of the location of the PP over the study area.

Modeling the Hydrologic Performance and Cost-Effectiveness of LID in a Residential Park Area Using a Decentralized Design Approach

Low Impact Development (LID) is one of the current research interests toward green infrastructures and urban flood control that have the capability to return developed watersheds to pre-development hydrological conditions, bringing numerous water quantity and quality benefits, while being cheaper than their traditional counterparts. However, there is a current research gap about LIDs within tropical regions. This study aims to evaluate the cost efficiency of LID scenarios in varying surface areas through a cost-effectiveness (C/E) analysis and to assess flow reduction and infiltration improvement of the cost-effective LID scenarios using US EPA Stormwater Management Model (SWMM) in a tropical residential catchment receiving an annual rainfall of 1780.5 mm (70.1″), under a Type 1 Philippine Climate. Results have shown that the Weibull plotting position generated the largest rainfall amounts. A total of 2112 manually simulated LID scenarios were modeled to obtain the cost-effective or optimal LID scenarios, where they can generate a maximum of 38.67% flow reduction and 29.73% peak flow reduction, all observed in the multiple LID scenarios. At high rainfall amounts, the multiple LID scenarios can also peak at a 1113% increase in total infiltration in the given sub-catchments. Determining the target capture goal, applicable LID types, and cost estimations from a pilot project are vital components in the future application of LIDs in these regions.

Drainage System Capacity Analysis with Storm Water Management Model (SWMM) at Cemarajaya Housing, Karawang Regency West Java

Purpose: This study aims to determine the factors that cause inundation/flooding in Cemarajaya Housing, evaluate existing drainage channels and plan drainage channels for unbuilt blocks and analyze the capacity of the drainage system using the EPA SWMM 5.1 program.
 Design/methodology/approach: Based on the simulation results using SWMM, the subcatchment response shows that an average of 22.11 mm per subcatchment is infiltrated and the rest becomes runoff of 310.23 mm.
 Findings: The abrasion disaster that hit the north coast of Karawang, especially the village of Cemarajaya, had occurred from around 1990 to 2016 and the most severe occurred in three hamlets, so residents affected by the abrasion had to be relocated to a place far from the shoreline. The Department of Public Housing and Settlement Areas of Karawang Regency built a housing estate to relocate residents affected by the abrasion disaster.
 Research limitations/implications: In this housing, 299 units of infiltration wells were built because the calculated channel dimensions were not possible to build due to the limited land area of the road.
 Practical implications: The problem that occurs in the housing is that the area where the housing construction is located is in the yellow zone based on the Karawang City/Regency Sanitation Strategic (SSK) data in 2017, which is an area prone to inundation of 25% to 50%. 
 Originality/value: This paper is originality
 Paper type: Research paper

Application and evaluation of LID facilities in sponge airport, China.

Low Impact Development (LID) is an important approach for the construction of sponge airports. There are few researches on the application of LID facilities in airports. This study mainly analyzes the application of LID facilities in airports, and analyzes the reduction rate of LID facilities on the total runoff, peak present time and peaking volume by constructing EPA Storm Water Management Model (SWMM) in the eastern work area of an airport, which is located in a coastal city in northern China. This study selected three kinds of LID facilities: green roof, bio-detention facility and permeable pavement. Then three LID scenarios were formed according to different layout ratios of facilities (30%-90%), and the effects of different scenarios under different design rainstorms are simulated and analyzed. The results show that the control effect of LID scenario is enhanced with the increase of the proportion of LID facilities. The control effect of LID scenario gradually weakened with the increase of rainfall intensity. For high-frequency rainstorm, the maximum reduction rates of total runoff and peaking volume are 30.89% and 25.58% respectively, and the peak present time delay rate is up to 28.57%. For low-frequency rainstorm, the maximum reduction rates of total runoff and peaking volume are 17.96% and 14.95% respectively, and the peak present time delay rate is up to 6.12%. The flood control effect is more obvious when the LID facilities and pipe network are combined under the condition of low-frequency heavy rain. These conclusions present the effects under different combination ratio of LID facilities. It can provide the technical reference for the design and application of LID facilities for sponge airport construction in the future.

Efficient Urban Runoff Quantity and Quality Modelling Using SWMM Model and Field Data in an Urban Watershed of Tehran Metropolis

This study aims to calibrate and validate the EPA Storm Water Management Model from field measurements of rainfall and runoff, in order to simulate the rainfall-runoff process in an urban watershed of Tehran metropolis, Iran. During and after three significant storm events, the flow rates, total suspended solids (TSS), total phosphorus (TP), and total Kjeldahl nitrogen (TKN) concentrations were measured at the outlet of the catchment, and were used in the model calibration and validation process. The performance of the SWMM model was evaluated based on the statistical criteria, as well as graphical techniques. In this study, a local sensitivity analysis was carried out to identify the key model parameters, show that “the percentage of impervious surface in each subwatershed had the most effect on the model output”. Based on the analysis of the results, SWMM model calibration and validation can be judged as satisfactory, and the goodness-of-fit indices for simulating runoff quality and quantity are placed in acceptable ranges. The adjustment obtained for the variations in the measured and simulated flow rates, pollutograph concentrations, total pollutant load, peak concentration, and the event mean concentration (EMC) confirms the considerable predictive capability of the SWMM model when it is well calibrated by using field measurements.

The Bellinge data set: open data and models for community-wide urban drainage systems research

Abstract. This paper describes a comprehensive and unique open-access data set for research within hydrological and hydraulic modelling of urban drainage systems. The data come from a mainly combined urban drainage system covering a 1.7 km2 area in the town of Bellinge, a suburb of the city of Odense, Denmark. The data set consists of up to 10 years of observations (2010–2020) from 13 level meters, 1 flow meter, 1 position sensor and 4 power sensors in the system, along with rainfall data from three rain gauges and two weather radars (X- and C-band), and meteorological data from a nearby weather station. The system characteristics of the urban drainage system (information about manholes, pipes, etc.) can be found in the data set along with characteristics of the surface area (contour lines, surface description, etc.). Two detailed hydrodynamic, distributed urban drainage models of the system are provided in the software systems MIKE URBAN and EPA Storm Water Management Model (SWMM). The two simulation models generally show similar responses, but systematic differences are present since the models have not been calibrated. With this data set we provide a useful case that will enable independent testing and replication of results from future scientific developments and innovation within urban hydrology and urban drainage systems research. The data set can be downloaded from https://doi.org/10.11583/DTU.c.5029124 (Pedersen et al., 2021a).

A Simplified Methodology for Optimal Location and Setting of Valves to Improve Equity in Intermittent Water Distribution Systems

In this paper, a simplified methodology to increase the water distribution equity in existing intermittent water distribution systems (WDSs) is presented. The methodology assumes to install valves in the water distribution network with the objective to re-arrange the flow circulation, thus allowing an improved water distribution among the network users. Valve installation in the WDS is based on the use of algorithms of sequential addition (SA). Two optimization schemes based on SA were developed and tested. The first one allows identifying locations of gate valves in order to maximize the global distribution equity of the network, irrespectively of the local impact of the valves on the supply level of the single nodes. Conversely, the second scheme aims to maximize the global equity of the network by optimizing both location and setting (opening degree) of control valves, to include the impact of the new flow circulation on the supply level of each node. The two optimization schemes were applied to a case study network subject to water shortage conditions. The software EPA Storm Water Management Model (SWMM) was used for the simulations in the wake of previous successful applications for the analysis of intermittent water distribution systems. Results of the application of the SA algorithms were also compared with those from the literature and obtained by the use of the multi-objective Non-Dominated Sorted Genetic Algorithm II (NSGA II). The results show the high performance of SA algorithms in identifying optimal position and settings of the valves in the WDS. The comparison pointed out that SA algorithms are able to perform similarly to NSGA II and, at the same time, to reduce significantly the computational effort associated to the optimization process.

A distributed heat transfer model for thermal-hydraulic analyses in sewer networks

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking. To predict efficiently water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the approach by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values ranging between 0.71 and 1.1. The results of our study show that modelled in-sewer wastewater temperatures are particularly sensitive to soil and headspace temperature, and headspace humidity. Simulation runs are generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration into urban planning, the SWMM-HEAT code is made publicly available.

Development and Application of a SWMM-Based Simulation Model for Municipal Scale Hydrologic Assessments

There is growing interest for the installation of green stormwater infrastructure (GSI) to improve stormwater control, increase infiltration of stormwater, and improve receiving water body quality. Planning level tools are needed to inform municipal scale decisions on the type and extent of GSI to apply. Here, a modified methodology is developed for the EPA Storm Water Management Model (SWMM) to create SWMM for Low Impact Technology Evaluation (SWWM-LITE) that enables municipal scale assessment of stormwater control measure (SCM) performance with minimal input data requirements and low processing time. Hydrologic outputs of SWMM-LITE are compared to those for SWMM and the National Stormwater Calculator (SWC) to assess the performance of SWMM-LITE. Three scenarios including the baseline without SCMs and the installation of varying SCMs were investigated. Across the three scenarios, SWMM-LITE estimates of annual average hydrologic performance (runoff, infiltration, and evaporation) were within +/−0.1% of estimates from a rigorously developed SWMM model in the City of Fort Collins, CO, for an evaluation of 30 years of continuous simulation. Analysis conducted for 2 year (y), 10 y, and 100 y storm events showed less than +/−2.5% difference between SWMM and SWMM-LITE hydrologic outputs. SWC provided reasonable estimates of hydrologic parameters for the case study area, but was designed for site level analyses of performance of SCMs rather than on the municipal scale. A sensitivity analysis revealed that the most sensitive parameters were primarily consistent for the SWMM-LITE and the complete SWMM. SWMM-LITE has low input data requirements and processing time and can be applied for assessing the hydrologic performance of SCMs to inform planning level decisions.

Optimal implementation of low impact development for urban stormwater quantity and quality control using multi-objective optimization.

Stormwater runoff is a major concern in urban areas which is mostly the result of vast urbanization. To reduce urban stormwater runoff and improve water quality, low impact development (LID) is used in urban areas. Therefore, it is vital to find the optimal combination of LID controls to achieve maximum reduction in both stormwater runoff and pollutants with optimal cost. In this study, a simulation-optimization model was developed by linking the EPA Storm Water Management Model (SWMM) to the Multi-Objective Particle Swarm Optimization (MOPSO) using MATLAB. The coupled model could carry out multi-objective optimization (MOO) and find potential solutions to the optimization objectives using the SWMM simulation model outputs. The SWMM model was developed using data from the BUNUS catchment in Kuala Lumpur, Malaysia. The total suspended solids (TSS) and total nitrogen (TN) were selected as pollutants to be used in the simulation model. Vegetated swale and rain garden were selected as LID controls for the study area. The LID controls were assigned to the model using the catchment characteristics. The target objectives were to minimize peak stormwater runoff, TSS, and TN with the minimum number of LID controls applications. The LID combination scenarios were also tested in SWMM to identify the best LID types and combination to achieve maximum reduction in both peak runoff and pollutants. This study found that the peak runoff, TSS, and TN were reduced by 13%, 38%, and 24%, respectively. The optimal number of LID controls that could be used at the BUNUS catchment area was also found to be 25.

Robust Vegetation Parameterization for Green Roofs in the EPA Stormwater Management Model (SWMM)

In increasingly expanding cities, roofs are still largely unused areas to counteract the negative impacts of urbanization on the water balance and to reduce flooding. To estimate the effect of green roofs as a sustainable low impact development (LID) technique on the building scale, different approaches to predict the runoff are carried out. In hydrological modelling, representing vegetation feedback on evapotranspiration (ET) is still considered challenging. In this research article, the focus is on improving the representation of the coupled soil–vegetation system of green roofs. Relevant data to calibrate and validate model representations were obtained from an existing field campaign comprising several green roof test plots with different characteristics. A coupled model, utilizing both the Penman–Monteith equation to estimate ET and the software EPA stormwater management model (SWMM) to calculate the runoff, was set up. Through the application of an automatic calibration procedure, we demonstrate that this coupled modelling approach (Kling–Gupta efficiency KGE = 0.88) outperforms the standard ET representation in EPA SWMM (KGE = −0.35), whilst providing a consistent and robust parameter set across all green roof configurations. Moreover, through a global sensitivity analysis, the impact of changes in model parameters was quantified in order to aid modelers in simplifying their parameterization of EPA SWMM. Finally, an improved model using the Penman–Monteith equation and various recommendations are presented.

Effect of spatial and temporal variability of gauged and radar rainfall data on hydrological modelingof urban basins

ABSTRACT In urban areas, rainfall-runoff modeling provides large uncertainties due to the difficulty in representing the spatial distribution of rainfall events. In this context, the this work aims to evaluate the effect of temporal and spatial of rainfall data (weather radar and distributed rainfall gauges network) on runoff estimation in a urban basin. The Reginaldo basin, inserted in the urban area of the Maceió city, capital of state of Alagoas (Brazil), has a reasonable availability of rainfall datal covered with a high number and spatial distribution of rain gauges and weather radar, which was used as input of a hydrological model The EPA Storm Water Management Model (SWMM) has been used with 3 analysis rainfall scenarios: (i) considering uniform rainfall distribution based on measured average rainfall, (ii) considering distributed rainfall using catchment discretization, and (iii) considering distributed rainfall using radar cell discretization. In order to evaluate the model outcomes, we analyzed four hydrological output variables: (i) the peak flow; (ii) the peak time; (iii) the volume flowed and (iv) the volume losses. Based on this criterion, it was clear that, considering he analyzed scenarios, the effect of spatial distribution of rainfall data on hydrological response in small urban basins, with high impervious coverage, was not divergent for the analyzed scenarios and that the radar data showed significantly higher data resolution than rainfall gauges.