Design Rainstorm Research Articles

Environmental Regulation and Stormwater Management Strategies for an Urban River in Northwest China: A Sustainable Approach

Low-impact developments (LIDs) have emerged as effective strategies for mitigating the adverse impacts of urbanization on river environments. This study aims to enhance river environment quality by examining the effects of LIDs and land use/cover change (LUCC) in the context of river environment and hydrological conditions. Using the Stormwater Management Model (SWMM) in an urban river setting, the study investigates the impact of LIDs on urban river water volume. An analysis of river runoff quality and quantity is conducted, followed by the development of an optimal river water regulation scheme through a multi-objective ecological scheduling model. The results reveal that the incorporation of LIDs can substantially decrease river runoff yield for varying recurrence periods of design rainstorms. Consequently, the flood peak reduction rate ranged from 10% to 18%, and the flood volume experienced a reduction of 10–29% in the study area. The combination of river water regulation, LIDs and LUCC leads to a decrease in river water volume within the lower river channel by up to 47% especially in a typical dry year and dry season, accompanied by a decline in river flow velocity and water self-purification capacity. A risk-based multi-objective stochastic optimization model is employed to ensure sustainable management of urban river runoff in terms of both quantity and quality. This research contributes to the advancement of knowledge in sustainable basin management practices and offers practical insights for policymakers involved in the management of water resources and environmental conservation in semi-arid basins.

Research on the design rainstorm calculation for the watershed in northern area of Xiamen New Airport

Urban design rainstorm is the basis of urban hydraulic engineering design, which is related to the safety and economy of urban drainage engineering, and has an important impact on the design scale and investment of urban drainage engineering. Scientific design rainstorm is the basis for ensuring the construction of hydraulic engineering.To ensure the safety of the new airport, government restarts the hydraulic engineering in the northern area of Dadeng Airport. This paper takes the northern area of Xiamen New Airport as the research object, and provides an effective pursuant for hydraulic engineering design through scientific design rainstorm ,and also provides a reference for other similar construction projects.

Impacts of rainstorm characteristics on flood inundation mitigation performance of LID measures throughout an urban catchment

The hydrological benefits of sponge city construction have sparked a variety of academic studies and discussions. However, the effectiveness of sponge city construction in mitigating flood inundation at the urban catchment scale remains rarely investigated. Therefore, the Jiaodong catchment in Zhenjiang City, which is a national sponge pilot city and has extensively implemented various LID measures, was selected as a study site. The SWMM-2DCA model was established and validated using measured rainfall and drainage pipe flow processes, as well as historical inundation-prone location records, and then applied to evaluate the accumulative effectiveness of LID measures in flood mitigation under different 2-hour design rainstorms with changing return periods (2, 5, 10, 20, and 30 years) and peak position coefficients (0.2, 0.5, and 0.8). The results revealed that nearly 90% of the inundated area had an inundation depth of less than 0.15 m, and the impact of rainstorm characteristics on the maximum inundation depth was very limited. Both the maximum inundation volume and area were positively related to the return period and the peak position coefficient of rainstorms. The increase in the rainstorm return period could advance the start of inundation and retard the occurrence of peak inundation. The maximum inundation volume and area could be significantly reduced by 63 ∼ 98% and 41 ∼ 96% respectively after the implementation of LID measures, but the average reduction rate for maximum inundation depth was only 3.7% for rainstorms with a return period longer than 10 years. This indicates that LID controls inundation better for volume and area than for depth. The changing patterns of absolute and relative reductions in maximum inundation volume and area with rainstorm characteristics exhibited reverse trends, while the absolute and relative reductions of maximum inundation depth demonstrated similar variations. The absolute reductions in both maximum inundation area and depth almost reached their extreme values at the 10-year rainstorm return period. The effects of LID on the timing of peak inundation depended largely on the peak position of rainstorms. These findings could contribute to a better understanding of the flood inundation mitigation performance of sponge city construction.

The Global Importance of Increasing Design Rainstorms under Specific Return Periods in China

Evaluating the correlation between changes in design rainstorms and extreme rainstorm events under climate change facilitates flood control and disaster reduction. Based on the daily rainfall data of 609 stations during 1958–2017, the Pearson-III curve, least square method, F-test, and other methods were adopted to study the changes in design rainstorms and the response to extreme rainstorms over nearly 60 years in China, and to explore the flood control capacity of engineering during climate change. The conclusions are as follows. (1) There is a general increasing trend in extreme rainstorm events in China. Most extreme rainstorm indices present upward trends in East China (EC), South China (SC), Central China (CC), Northwest China (NW), and Southwest China (SW) and downward trends in Northeast China (NE) and North China (NC). (2) The temporal series of design rainstorms shows general growth under each return period in China. In EC, SC, and SW, the design rainstorms increase significantly with rates of 3.0, 3.1, and 1.3 mm/10a, respectively, in the 20-year return period, while they decrease significantly by −2.0 mm/10a in NC (p < 0.05). (3) Design rainstorms have a positive response to extreme rainstorm events, which resulted in increasing rainstorms in a specific return period in EC, SC, NW, and SW. These results can promote the revision of engineering design standards and improve the flood control capability of engineering.

Study on Hydrological Calculation Model of Flood Control in the Middle and Lower Reaches of the Chuhe River under the Background of Urbanization

The traditional method of hydrology and water conservancy calculation is based on the assumption of natural runoff, while the applicability of method has weakened in the urbanization-affected river basins. The paper carried out research on hydrological calculation model of flood control in the middle and lower reaches of the Chuhe River under the background of urbanization. On the basis of the analysis of flood characteristics in river basins, the hydrological calculation model framework of flood control in the middle and lower reaches of the Chuhe River is constructed, which includes five modules: design rainstorm calculation, runoff calculation, regional flow concentration calculation, river-network confluence calculation and lake-reservoir regulation calculation. The parameters of runoff generation, overland flow concentration, hilly area flow concentration and river-network confluence are determined. Process simulation of the flood water levels and discharges in the middle and lower reaches of the Chuhe River in 1991 and 2008, which are the years with heavy rains, is conducted. The flood simulation of June 1991 shows that the error of water level is -1cm ~ + 8cm, and the error of discharge is +26 m3/s. The flood simulation of August 2008 shows that the error of water level is -8cm ~ + 2cm, and the error of discharge is -9 m3/s. The overall simulation results are relatively stable with all the calculation errors within the allowable range, and the results fit the facts well.

Assessment of compound flooding through seamless linkage of coastal hydrodynamic and inland catchment models

Compound flooding refers to the complex interactions among oceanographic, inland (catchment) hydrological, and meteorological processes with anthropogenic factors such as land use changes due to urbanization. To-wit, the impact of higher tide levels, storm surge, and high intensity rainfall events over the inland catchment collectively may result in more extensive flooding than the individual processes acting separately. In the context of climate change and more frequent extreme weather events, coastal cities, particularly those in the ASEAN region, are increasingly vulnerable to compound flooding, yet there is no convenient and user-friendly modelling approach available that would enable the planning community and decision-makers to envision compound flooding as part of resiliency-oriented urban plan development. We addressed this gap by developing the3D Resiliency Visualisation Platform (3DRVP), within which linked features are established using Python scripts to seamless integrate a 2D mixed land use fluvial/pluvial catchment model (PCSWMM) with a 2D/3Dcoastal hydrodynamic model (Delft3D) to simulate the dynamics ofcompound floods for the assessment of coastal inundation. This platform aims to assist planners, urban design professionals, and engineers with a realistic visualization tool to picture the urban infrastructure planning alternatives as well as to facilitate the real-time operational decision-making and evacuation activation with flood control strategies. The integrated platform theory is developed first and the platform then is trialled for a developing coastal area in south Bangkok, Thailand. Similar to many cities of the global south, data availability to calibrate models is limited and as such we used a mixed methods approach to explore model accuracy. The Delft3D model was calibrated successfully using water level data from a nearby gauge in the Gulf of Thailand for Typhoon Linda. The catchment model (PCSWMM) was validated using observed flood areas as reported by the local municipality. A 100-year design rainstorm was subsequently modelled and linked with the Typhoon Linda surge levels with results indicating the combination of rainfall flooding and storm surge would increase the flooded area by 25.6% over the system components modelled individually.

An overall optimization and solution framework for urban historical and future DRIF under climate change

Abstract The estimation and application of Intensity-Duration-Frequency (IDF) curves depend on the assumption of stationarity of the rainfall series, which is that the intensity and frequency of extreme hydrological events remain unchanged in the future. Climate change will have a significant impact on the collection and utilization of rainwater and its spatial characteristics. When the Gray-Green infrastructure is designed, if only historical precipitation is adopted to calculate the urban design rainstorm intensity formula (DRIF) and the total annual runoff control rate, it may be difficult to meet the demand of future precipitation changes on the city's ability to accommodate rainfall. Therefore, it is very important to study the impact of climate change on the IDF curve. This study proposes an overall optimization solution framework for historical and future DRIF. The impact of the extreme value on the IDF curve during the historical period is analyzed. The calculation method of the IDF curve in the future period is established. The changes of the rainstorm intensity in the historical and future period (SSP1-2.6,SSP2-4.5,SSP3-7.0,SSP5-8.5) were analyzed for the 15 durations and eight return periods in Beijing, China. The results of this study show that the nondominated sorting and local search (NSLS) has the best accuracy in fitting the statistical samples of precipitation for different durations. The best methods to judge and process the extreme value of the statistical sample are Z-score and average value of series greater than critical value (AVG). Under the four SSP scenarios, the estimated IDF value is larger than the observed value in the historical period. The results of the equivalent return period calculated using the DRIF show that the the four SSP scenarios are smaller than the historical period for the return period greater than five years. Taking 120 min of short-duration precipitation as an example, the 100-year equivalent return periods of the observation under the four SSP scenarios are 35-, 20-, 54-, and 17-years, respectively. The research can provide valuable reference for the design and planning of the drainage facility under climate change.

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.

A GPU-Accelerated Hydrodynamic Model for Urban Rainstorm Inundation Simulation: A Case Study in China

Frequent urban rainstorm inundations can cause serious damages to human life and social economy. Reliable simulation of urban rainstorm inundation is an effective approach for performing flood risk analysis to reduce losses. In this work, a full 2D high-performance hydrodynamic model for urban rainstorm inundation simulation based on Graphic Processing Unit (GPU) was developed. The idealized V-shape catchment and sponge city district of Fengxi New City were selected as the study areas to assess performance of the model. The model was validated against analytical benchmark results of the idealized V-catchment test which show good agreement between the modelled flow and analytical solutions. The model was then applied to simulate actual urban rainstorm inundation process under measured rainfall. The results indicated that the model can be applied to high-resolution urban region simulations. Specifically, the validation results indicated that the proposed model had a good performance, with an accepted error of less than 15%. When applied to compute the Fengxi New city under design rainstorms with different annual return periods of 1, 5, 10, 20, 50, and 100 years, it was found that the model effectively evaluated the temporal and spatial variation process of urban inundation, and quantitatively investigated flood risks according to the water depth change. The model has been substantially accelerated on GPU to quickly predict urban inundation. The accuracy and rapid simulation speed of the model were verified based on the actual study area. Therefore, the proposed model can help to predict the dynamic processes of urban flood inundation and thus reduce flood inundation disasters. This is essential for future optimal sponge urban construction planning in China.

Surface runoff response to long-term land use changes: Spatial rearrangement of runoff-generating areas reveals a shift in flash flood drivers

Nowadays, rapid growths of urban areas and associated land use/land cover (LULC) changes notably affect the surface runoff response to rainfall in urbanised catchments. This effect of urbanisation on surface runoff is frequently addressed since it relates to the increasing incidence of pluvial floods worldwide. Studies on this issue commonly assess runoff changes over several most recent decades. However, human-induced factors likely resulted in increased surface runoff and associated flash floods in rural catchments even in the past centuries. Such long-term changes have been rarely studied and thus are not well documented. This paper aims to fill this gap and assess the surface runoff response to LULC changes in a small catchment in southwestern Slovakia over more than two centuries. To meet this goal, we applied the Soil Conservation Service Curve Number (SCS-CN) method. We mapped past (1784) and present (2018) LULC classes based on historical maps and modern remote sensing data. Then, we estimated surface runoff depths for specific design rainstorms for both periods by executing CN method equations in the ArcGIS environment. Results revealed significant changes in surface runoff conditions between evaluated periods. In total, surface runoff magnitudes increased by ~230 and ~ 130% for 40- and 65-mm design rainstorms, respectively, compared to 1784. Moreover, surface runoff values show different spatial patterns on historical and present-day output raster images revealing spatial redistribution of runoff-enhancing and runoff-preventing areas during the evaluated period. Although both infiltration-enhancing and runoff-enhancing effects of LULC changes were identified, the latter effect associated with urbanised lowland areas was recognised as prevailing at present. In contrast, runoff-promoting conditions were associated with hilly vineyard areas in the past. These findings likely have important implications for understanding the past and present LULC-based controls of surface runoff generation and flash floods initiation.

Impacts of Climate Change on Urban Drainage Systems by Future Short-Duration Design Rainstorms

The adverse impacts of climate change and urbanization are converging to challenge the waterlogging control measures established in the Dong Hao Chong (DHC) Basin. Based on representative concentration pathway (RCP) scenarios, the future (2030–2050) waterlogging was assessed for the DHC basin and combined with future design rainfall. The delta change factors were projected using the regional climate model, RegCM4.6, and the annual maximum one-day rainstorm was modified to develop the annual maximum value method. By combining the delta change and annual maximum value methods, a future short-duration design rainstorm formula is developed in this study. The Chicago hyetograph shapes indicated that the peak rainfall intensity and amount both increase in the five return periods with two RCP scenarios. The InfoWorks ICM urban flood model is used to simulate the hydrological response. The results show that climate change will exacerbate urban waterlogging in DHC Basin. The maximum inundation volume and number of inundation nodes were expected to increase in the five return periods under the RCP4.5 and RCP8.5 scenarios, respectively. The submerged area is increasing due to climate change. This study highlights the link between climate change and urban drainage systems, and suggests that the effect of climate change in extreme rainfall should be considered in urban waterlogging management and drainage system design.

Analysis about the impacts of changing basin underlying surface on design floods for design units of water diversion projects

After the water diversion project has been put into operation for many years, due to the long distance, complex hydro-meteorological conditions, and rapid development of social economy, the underlying surface conditions of corresponding natural basins in the design units of water diversion project have changed to some extent compared with the beginning of the project design, especially the underlying surface situation of rivers in the northern region has changed greatly. Based on ArcGIS to extract basin characteristic values of the design unit of water diversion project, such as basin area, river length and slope, this paper analyzes the changes of current basin characteristic values of design unit compared with the design period. For the design unit with significant changes in the basin characteristics, the original design flood calculation method is used to calculate the flood of the same design rainstorm under current conditions, and the impacts of changing basin underlying surface on design floods are analyzed. PACS: J0101

The application of big data in the analysis of the impact of urban floods: A case study of Qianshan River Basin

In recent years, with the acceleration of climate change and urban modernization, the flood risk of economic and social development has increased. The problem of urban flood disasters needs to be solved urgently. It is particularly important to conduct flood disaster loss assessment research for further flood control and disaster reduction, and emerging big data have opened a new direction for solving the problem of urban flooding. In this study, the Qianshan River Basin in Guangdong Province was used as an example. The TELEMAC model was used to simulate the inundation process under the design rainstorms of 50a and 100a in the Qianshan River Basin. Based on the heat map service, route planning service, and search service functions of Baidu Maps and Amap open platforms, this study used crawler technology to integrate multi-source data, including traffic survey data, geospatial data, population heat map data at different times (day/night) on weekdays and non-weekdays, and point of interest (POI) data from various industries. A dynamic assessment model of flood disaster loss for traffic, population, and POIs was constructed. The research results could greatly improve the timeliness and accuracy of urban flood disaster analysis, early warning, monitoring, and disaster risk assessment.

Coupling of SWMM With 2D Hydrodynamic Model for Simulation of Sponge City Construction Scheme

Sponge city is a new urban stormwater management concept proposed by China to solve the urban water environment and security problems. The stormwater management model (SWMM) is one of the most commonly used urban stormwater and sponge city simulation models. SWMM is coupled with a two-dimensional hydrodynamic model based on the finite volume method to establish a coupled 1D and 2D hydrodynamic model in this research. The coupled model can simulate the drainage pipe network, sponge measures and flood inundation at the same time. A predictor-corrector method with good stability was used in the coupled model to ensure the non-negativity of the water volume of the 2D model cell. The sponge city construction scheme for a community in Beijing was simulated and analyzed using several design rainstorm processes with different return periods based on the proposed model. It is proved that the coupling model can be applied to sponge city construction problems and sponge measures can reduce the flood inundation and the load of drainage network system by simulating the drainage conditions and ground waterlogging before and after the reconstruction of the drainage community.

A stress test of urban system flooding upon extreme rainstorms in Hong Kong

Many cities face high flood risks due to intense rainstorms and dense urban environments. Quantifying the degree and duration of flood impact to urban systems under extreme rainstorms is essential for long-term flood risk management and short-term emergency response. This study aims to develop a novel stress testing framework for evaluating urban system flooding upon extreme rainstorms in Hong Kong. The stress testing framework is based on a pipe-surface coupled hydraulic model for detailed flood simulation in urban settings and a dynamic flood impact evaluation method for assessing interruptions to urban transportation and building systems. The proposed stress testing method is applied to assess the flood impacts in Kowloon, the most densely populated area in Hong Kong. Detailed urban settings such as engineering drainage facilities and buildings are incorporated into the flood simulation model, and the model is validated both qualitatively and quantitatively by field observations. Flood hazard scenarios are investigated under design rainstorms of different return periods (20, 100, and 1000 years), and the impacts on transportation and building systems are evaluated with the new process-based impact evaluation method. The results of the case study indicate that underground mass transit railway (MTR) stations and residential buildings will be more affected than highways and other types of buildings in Kowloon: up to 56% of MTR stations and 43% of residential buildings may be affected under the 1000-year rainstorm, with inundation durations of 8 and 7 h for the MTR stations and residential buildings, respectively. To ensure public transportation services and reduce potential exposure of residents during extreme rainstorms, mitigation measures should be taken to reduce the affected percentage and duration of MTR stations and residential buildings. The proposed methods contribute to enhanced societal flood preparedness, warning, and response.

Evaluation of Permeable Brick Pavement on the Reduction of Stormwater Runoff Using a Coupled Hydrological Model

In several cities, permeable brick pavement (PBP) plays a key role in stormwater management. Although various hydrological models can be used to analyze the mitigation efficiency of PBP on rainfall runoff, the majority do not consider the effect of multi-layered pavement on infiltration in urban areas. Therefore, we developed a coupled model to evaluate the potential effect of PBP in reducing stormwater runoff at a watershed scale. Specifically, we compared the hydrological responses (outflow and overflow) of three different PBP scenarios. The potential effects of PBP on peak flow (PF), total volume (TV), and overflow volume (OV) were investigated for 20 design rainstorms with different return periods and durations. Our results indicate that an increase in PBP ratio reduces both PF (4.2–13.5%) and TV (4.2–10.5%) at the outfall as well as the OV (15.4–30.6%) across networks. The mitigation effect of PBP on OV is linearly correlated to storm return period and duration, but the effects on PF and TV are inversely correlated to storm duration. These results provide insight on the effects of infiltration-based infrastructure on urban flooding.

Urban flood inundation and damage assessment based on numerical simulations of design rainstorms with different characteristics

Urban flood inundation and damage assessment based on numerical simulations of design rainstorms with different characteristics

Real-time error correction of two-dimensional flood-inundation simulations during rainstorm events

This study develops a real-time error correction model named RTEC_2DIS for two-dimensional (2D) flood-inundation simulations. Inundation depth and flooding area provided by a 2D numerical hydraulic modeling (SOBEK model) are corrected in accordance with real-time observations at specific road-based water-level gauges. The proposed RTEC-2DIS method can estimate the forecast error of inundation depths for various lead times at both gauged grids and ungauged grids within the watershed/basin. By doing so, the real-time correction of the resulting inundation area composed of corrected water-depth forecast at all concerned grids can be achieved by adding the water-depth forecasts to the corresponding forecast errors. In this study, the demonstration of the model is made in the Tainan district in Southern Taiwan under the consideration of the design rainstorm events of specific return periods with a central-peak storm pattern and a real rainstorm event from Typhoon Megi in 2016. The results from the numerical demonstration indicate that the RTEC-2DIS method can effectively reduce the uncertainty in the estimating inundation depth at gauged grids to enhance its correction performance with the percentage of error reduction of 42% in the case of the real rainstorm event. Furthermore, regarding the design events, through the proposed RTEC-2DIS method, the accuracy of the simulated inundation area can be improved by 55%. In summary, the proposed RTEC-2DIS method not only can correct forecasted inundation depths at gauged grids, but also facilitate the accuracy and reliability of the resulting inundation area in accordance with real-time observations recorded at road-based water-level gauges.

Modelling and Application of Urban Drainage Based on Mike Urban Model

To alleviate the drainage pressure of urban pipeline network and reduce flood disaster, for the problem of non-convergence of design standards caused by inconsistency of design rainstorm duration between urban construction and water conservancy departments, this paper takesa residential district in Wenzhou City of Zhejiang Province as an example, andanalyze the relationship of recurrence periods between pipeline network drainage and waterlogging drainage under the regulation and storage capacity of rivers. Mike Urban was used to establish the drainage model of pipeline network to simulate the drainage situation when facing different river water levels at the outlet. The results are as follows: (1) when the recurrence period of pipeline design is 1 year, 3 years and 5 years respectively, the corresponding design rainstorm recurrence period of waterlogging drainage is about 5 years, 15-20 years, 20-30 years; (2) when meeting the high the water level at the outlet, the once a year rainfall of pipeline network encountering is equivalent to that of the pipeline network encountering the once a year to once in three years rainfall when the water level of the outlet is constant; (3) when the water level at the outlet is high, the once in three years rainfall of the pipeline network encountering is equivalent to that of the pipeline network encountering the once in three years to once in five years rainfall when the water level of the outlet is constant. Relevant research can provide reference for the design standard of pipeline network.

Damage assessment of infrastructure based on urban flood inundation simulation

Flood is a serious challenge that increasingly produce immense economical and ecological damages in worldwide. Flood simulation is gradually becoming a central focus of the hydrology in recent years. It is worthwhile to combine flood simulation with flood damage to infrastructure. The purpose of this study is to develop an approach for better urabn flood simulation at different return periods and assess the damage of flood to infrastructures in different return period. The approach is organized into four parts: design rainstorm event simulation, runoff simulation, flood inundation simulation and submerged infrastructures extraction. Base on the flood simulation, we draw the flood inundation map of Xuanwu-Qinhuai-Jianye-Gulou-Yuhuatai (XQJGY) region. Results indicated that the transportation infrastructures suffer the largest proportion of flood damage. This study simulates the inundated infrastructure at different return periods, provides a theoretical support for flood risk management.