SWMM-Based Assessment of Urban Mountain Stormwater Management Effects under Different LID Scenarios

The types of urban mountains are diverse, and the surrounding environment is complex. The conditions of runoff generation and convergence in different regions of the same mountain vary. Using the Lijia Mountain in China’s Nanjing City as a case study, this study investigates the effects of such mountain-region-based LID (Low Impact Development) systems. Based on the hydrological analysis of this mountain region, SWMM (Storm Water Management Model) software is used to model and compare the runoff control effects of two LID systems schemes, namely segmental detention and retention and terminal detention and retention. The study’s findings demonstrate that the terminal detention and retention scheme can effectively delay the time of peak flooding and partly reduce peak discharge. In contrast, the segmental detention and retention scheme has a limited delay effect on flood peaks but significantly reduces the peak discharge. This research breaks through the limitations of the previous construction of a single LID scheme for mountainous regions in built-up urban areas. It serves as a theoretical model and technical reference for selecting LID scenarios in response to different mountain conditions.

Modeling the quality of sewage during the leaking of stormwater surface runoff to the sanitary sewer system using SWMM: a case study

This paper describes the application of the storm water management model (SWMM) for predicting the sewage quality in the sanitary sewer system of the study area resulting from the leaking of stormwater surface runoff to the system during rainfall events at different return periods. The concentrations of major pollutants were assessed in the sanitary sewer system at different rainfall intensities. Then, a solution to mitigate the problem was proposed using low impact development (LID) technology. The results of sensitivity analysis indicated that maximum build-up possible was the most sensitive parameter for model calibration. The model was calibrated using actual rainfall events, and statistical validation coefficients of R (0.81–0.82) and NMSE (0.0173–0.022) proved that the model is valid. The sewage quality assessment results showed that pollutants concentration increased to its maximum level at 20 min and gradually decreased to a slightly constant minimum value after 2 h. The proposed solution of LID reduced the pollutants concentrations by 82–88, 75–77, 52–55, and 7–10% for all pollutants at return periods of 2, 5, 10, and 25 years, respectively. To conclude, SWMM simulation successfully predicted the concentration of the pollutants, and leaking of stormwater surface runoff has changed the sewage quality.

Case Study of Urban Flood Inundation—Impact of Temporal Variability in Rainfall Events

This study aimed to calculate and analyze total overflows that accumulate in urban manholes in the target drainage basin of Samsung-dong, Seoul in heavy rainfall events with different temporal distribution characteristics, using the EPA’s Storm Water Management Model (EPA-SWMM model). Inundation behaviors were analyzed using the two-dimensional flood model (FLO-2D). The extreme rainfall events were produced using different exceedance probability Huff distributions for different durations and return periods, such as from 1 to 3 h and 10 years, 50 years, 80 years, 100 years, respectively. The inundation model was validated using the actual flood observations on 21 September 2010 in the Samsung-dong drainage basin. The total overflow amount showed considerable differences according to the different time distribution characteristics, such as the temporal location of the storm peak and the concentration level of the storm. Furthermore, the inundation behaviors were also related to the temporal characteristics of storms. The results illustrated that the consideration of the temporal distribution characteristics of extreme rainfall events is essential for an accurate understanding of the rainfall–runoff response and inundation behavior in urban drainage basins.

Study on the different type of hydrological input towards the accuracy of catchment discharge hydrograph

For hydrological applications, several rainfall measurement techniques are available, each with its own spatial and temporal resolution and errors. When these rainfall datasets are used as input for hydrological models, errors and uncertainties are propagated throughout the hydrological system. This research paper is using rainfall data from two different measurement tools namely rain gauge and radar. Using these two types of measurement tools, it is expected dissimilar output due to the different working principle. Arau catchment in Perlis were selected as the study area. The rainfall data used is in the unit of intensity with time interval 10 minutes for both instruments. Storm Water Management Model 5 (SWMM5) were used as model to simulate the discharge of catchment area. Sensitivity analysis is carried out in this study to determine the major parameters that influence to shape of hydrograph and peak flow. Then, calibration process using five (5) storm events have been performed using available information such as conduits lengths, shape of conduits, impervious and pervious surface using trial and error process. Good correlation between observed and simulated hydrograph on 18 September 2006 has been found to be the best Correlation coefficient (r) and Root mean square error (RMSE) equal to 0.92 and 0.14 respectively. The same parameter used for that storm event was chosen to be applied in validation event. Validation results also in the acceptable range with r is found more than 50% correlation. Next, using the rainfall data captured by radar that converted using equation Z=40R1.6 developed by researcher [1] for the similar date of storm event and similar catchment conditions, all the hydrograph shape shows significant drop. As a conclusion, different type of measurement tools for rainfall gives significant different to the catchment discharge and can be seen that rain gauge are better to use to simulate rainfall compared to the radar.

Urban Stormwater Modeling with Local Inertial Approximation Form of Shallow Water Equations: A Comparative Study

This study focused on the performance and limitations of the local inertial approximation form model (LIM) of the shallow water equations (SWEs) when applied in urban flood modeling. A numerical scheme of the LIM equations was created using finite volume method with a first-order spatiotemporal Roe Riemann solver. A simplified urban stormwater model (SUSM) considering surface and underground dual drainage system was constructed based on LIM and the US Environmental Protection Agency Storm Water Management Model. Moreover, a complete urban stormwater model (USM) based on the SWEs with the same solution algorithm was used as the evaluation benchmark. Numerical results of the SUSM and USM in a highly urbanized area under four rainfall return periods were analyzed and compared. The results reveal that the performance of the SUSM is highly consistent with that of the USM but with an improvement in computational efficiency of approximately 140%. In terms of the accuracy of the model, the SUSM slightly underestimates the water depth and velocity and is less accurate when dealing with supercritical flow in urban stormwater flood modeling. Overall, the SUSM can produce comparable results to USM with higher computational efficiency, which provides a simplified and alternative method for urban flood modeling.

Evaluation and Optimization of Low Impact Development Designs for Sustainable Stormwater Management in a Changing Climate

The increasing intensity and frequency of extreme storms pose a growing challenge to stormwater management in highly urbanized areas. Without an adequate and appropriate stormwater system, the storms and associated floods will continue to cause significant damage to infrastructure and loss of life. Low Impact Development (LID) has become an emerging alternative to the traditional stormwater system for stormwater management. This study evaluates and optimizes applications of different combinations of LIDs to minimize flows from a catchment under past and future storm conditions. The Storm Water Management Model (SWMM), forced by observed and downscaled precipitation from Coupled Model Intercomparison Project phase 6 (CMIP6), was used to simulate the runoff and apply the LIDs in the Renton City, WA. The final results show that the performance of LIDs in reducing total runoff volume varies with the types and combinations of LIDs utilized. A 30% to 75% runoff reduction was achieved for the past and future 50 year and 100 year storms. The study demonstrates the effectiveness of LID combinations with conventional stormwater systems to manage the future runoff in the study area, which is expected to increase by 26.3% in 2050.

Study on the Application of Clustering Method in the Determination of Uncertainty Parameters of SWMM Model

Storm Water Management Model (SWMM) is one of the most commonly used models in urban flood simulation. However, because the calibration and verification of the model's uncertainty parameters are extremely dependent on the measured flood data, it is difficult to apply the model in areas lacking data. This study proposes a parameter sample clustering method based on peer research results to determine the uncertainty parameters of SWMM, and compares the simulation results with the simulation results of the manual adjustment method based on measured data. The research shows that the Absolute error (AE), Relative error (RE), Nash efficiency coefficient (NSE), and Coefficient of determination (R2) of the water depth simulated by the parameter sample clustering method are 0.040m, 9.08%, 0.949, 0.967 compared with the measured value, respectively. The value of AE, RE, NSE, and R2 of the manual tuning method during the calibration simulation period are 0.066m, 15.95%, 0.881 and 0.924, respectively. Therefore, the parameter sample clustering method has a better simulation effect than manual tuning method, and it can be further promoted in areas without flood data.

Application of PCSWMM for the 1-D and 1-D–2-D Modeling of Urban Flooding in Damansara Catchment, Malaysia

Coupled with climate change, the urbanization-driven increase in the frequency and intensity of floods can be seen in both developing and developed countries, and Malaysia is no exemption. As part of flood hazard mitigation, this study aimed to simulate the urban flood scenarios in Malaysia’s urbanized catchments. The flood simulation was performed using the Personal Computer Storm Water Management Model (PCSWMM) modeling of the Damansara catchment as a case study. An integrated hydrologic-hydraulic model was developed for the 1-D river flow modeling and 1-D–2-D drainage overflow modeling. The reliability of the 1-D river flow model was confirmed through the calibration and validation, in which the water level in TTDI Jaya was satisfactorily predicted, supported by the coefficient of determination (R2), Nash–Sutcliffe model efficiency coefficient (NSE), and relative error (RE). The performance of the 1-D–2-D model was further demonstrated based on the flood depth, extent, and risk caused by the drainage overflow. Two scenarios were tested, and the comparison results showed that the current drainage effectively reduced the drainage overflow due to the increased size of drains compared to the historic drainage in 2015. The procedure and findings of this study could serve as references for the application in flood mitigation planning worldwide, especially for developing countries.

Influence of storms on the emission of pollutants from sewage into waters

During heavy precipitation, chemical and biological pollutants from urban and agricultural areas enter the waters from storm overflows as a result of infiltration and inflow, as well as via uncontrolled outflows from water treatment plants. Infiltration and inflow of rainwater into sewers is an especially popular and major worldwide problem. Climate forecasts indicate changes in climatic conditions towards an increase in the intensity and frequency of torrential rainfalls. It may therefore be assumed that the negative impact of rainwater on water quality will increase. This article attempts to address the question of the impact of pollution from wastewater introduced into water during rainy weather to the receiver. The assessment of the impact of rainfalls on a receiver was carried out on the basis of a simulation of pollution loads from sewage introduced into a river by storm overflows based on data from monitoring the amount of rainfall and simulating the operation of storm overflows using Environmental Protection Agency Storm Water Management Model (EPA SWMM). The obtained results were compared with the pollutant loads discharged at the same time from the sewage treatment plant (STP). In addition, the article assesses possible improvement solutions to reduce the negative impact of storm overflows on water.