Urban Rainstorm Research Articles

MAS-Based Evacuation Simulation of an Urban Community during an Urban Rainstorm Disaster in China

The frequent occurrence of urban waterlogging constantly affects cities’ stability, bringing about a lot of economic losses and casualties. Coupled with the deficient rescue activities, waterlogging often exacerbates the impact of urban rainstorm disasters. By setting up a diverse distribution of shelters and various types of pedestrians, the evacuation route choice of pedestrians in an urban rainstorm disaster is simulated and analyzed through multi-agent system simulation. Then, clustering analysis is applied to discover population characteristics in different survival scenarios. The simulations for sustainable rescue after pedestrians reach the shelters are also carried out. It was found that the pedestrians’ herd mentality and the distribution of shelters have a significant impact on the success rate of post-disaster evacuation. The results could help pedestrians to make decisions in the evacuation. The wide scope of the shelters’ allocation facilitates the effect of disaster relief.

Spatial simulation of rainstorm waterlogging based on a water accumulation diffusion algorithm

This study presents a water accumulation diffusion algorithm to spatially simulate rainstorm-induced waterlogging for people’s lives and property safety. Taking part of Jinfeng District in Yinchuan City, China, as a study area, a storm water management model (SWMM) model is constructed with the aid of geographic information system (GIS) and remote sensing (RS) technologies. GIS is used to divide sub-catchments, generalize drainage system, set parameters, construct spatial geodatabase, and identify flood extents and depths. RS is used to obtain land-use/land-cover information. The water accumulation diffusion algorithm is then designed using the strategies of the dynamic interactions between pipes and surface and between central pixel and its neighbourhood pixels to transform water accumulation volume of sub-catchment into the submerged range and water accumulation depth. Positions, extents, depths, and volumes of water accumulation from pipe network and surface are simulated, respectively. The spatial simulation precisions of rainstorm waterlogging from the pipe network and surface are verified according to the measured and cyber rainstorm data, respectively. The results show that (1) the number of water accumulation nodes increases with the increase of rainfall intensity; (2) urban waterlogging is mainly distributed in the intersects of roads, low depressions and the aged drainage networks; and (3) spatial simulation of urban rainstorm waterlogging based on the GIS, RS, and SWMM techniques and the water accumulation diffusion algorithm is reliable. The results can provide decision-makings to predict rainstorm waterlogging, design drainage network, and construct a sponge city.

Assessment of GPM IMERG and radar quantitative precipitation estimation (QPE) products using dense rain gauge observations in the Guangdong-Hong Kong-Macao Greater Bay Area, China

The recent intensification of extreme rainfall events has the potential to aggravate the frequency and intensity of floods in urban areas and signals the urgent need for accurate and high spatiotemporal resolution precipitation data for flood monitoring and warning to alleviate the associated damages. In this context, this paper aims to statistically assess the latest Integrated Multisatellite Retrievals from Global Precipitation Measurement (IMERG) multisatellite constellation and radar quantitative precipitation estimation (QPE) products against dense rain gauge network observations under multiple temporal scales (hourly and 3-hourly) and three spatial scales (grid cumulative, regional, and grid) over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in China. The results indicate that (1) at the grid cumulative scale, QPE significantly outperforms IMERG products. The correlation coefficients of QPE (0.83 ≤ CORR ≤ 0.85) are much higher than those of IMERG products (0.35 ≤ CORR ≤ 0.56), the estimation of QPE is generally significantly underestimated (−0.23 ≤ BIAS ≤ -0.16), and the BIAS of IMERG products is larger than that of QPE (−0.24 ≤ BIAS ≤ 0.23). (2) At the regional scale, the accuracy of IMERG products has been significantly improved, with relatively high correlation coefficients (CORR≥0.8) and decreased root mean squared error (RMSE) values (1.18 mm ≤ RMSE ≤ 0.22 mm), and Taylor diagrams visually show that QPE is closer to the gauge observations than are IMERG products. (3) The evaluation results at the grid scale show that both IMERG products and QPE can accurately reflect the spatial distribution of precipitation. Among these results, the spatial distribution of QPE is the most consistent with the actual rainfall, although an obvious underestimation of rainfall occurs in areas with strong rainfall. (4) In terms of detection indicators, the three IMERG products are superior to QPE at capturing rainfall events and have more advantages over QPE in the estimation of instantaneous precipitation, especially for light rain events. However, QPE has better detection effects for rainfall events under rainstorm and heavy rainstorm events, indicating the hydrologic utility of this product. Among the three IMERG products, the IMERG Early Run (ER) product has the advantages of a short lag time and high accuracy, and it has the potential to be applied in flood forecasting. Future studies should improve IMERG algorithms and promote the application of QPE in urban rainstorm and flood research.

Risk Assessment of Urban Waterlogging Based on GIS

In this paper, based on ArcGIS spatial analysis technology, taking Tongshan County as an example, the risk index evaluation model of urban rainstorm waterlogging disaster is established. In the comprehensive risk assessment and regional research, the weight of each risk index is determined by analytic hierarchy process (AHP), and the fuzzy evaluation is applied to the raster data of GIS risk index, so as to realize the data management of risk index, the combination of spatial analysis and visual expression. The results of risk assessment classification and regionalization can provide technical support and decision support for urban waterlogging risk prevention and disaster reduction planning in Tongshan County.

Multiscale Variability of Precipitation and Their Teleconnection with Large-scale Climate Anomalies: A Case Study of Xi'an City, China

Wang, X.; Jiang, R.; Xie, J.; Zhao, Y.; Li, F., and Zhu, J., 2019. Multiscale variability of precipitation and their teleconnection with large-scale climate anomalies: A case study of Xi'an city, China. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 417–426. Coconut Creek (Florida), ISSN 0749-0208.The changes of precipitation affect the urban rainstorm waterlogging and water resources management, which have important influences on the sustainable development of society. The primary objective of the paper is to provide theoretical basis for local water resources management and disaster prevention and reduction by analyzing the multiscale variability of precipitation and their teleconnection with large-scale climate anomalies in Xi'an city of China. The change characteristics of precipitation and extreme precipitation indices were investigated using Mann-Kendall test, Spearman's rank correlation and wavelet analysis. The cross wavelet transform and wavelet coherence were used to explore the correlations between the precipitation and large-scale teleconnection indices such as Arctic Oscillation (AO), Southern Oscillation Index (SOI), El Nino-Southern Oscillation (ENSO) and sunspot. Results indicate that: the precipitation was mainly concentrated in summer, followed by autumn. The annual, seasonal and monthly precipitation except June and August had decreasing trends, and the magnitudes of precipitation decrease were more pronounced in spring, April and November. The change patterns varied for extreme precipitation indices. The temporal variation in extreme precipitation indices indicated that the extreme precipitation events had mainly increased during 1971-1990 and 1991-2017, and decreased during 1951-1970 and 1951-2017, especially, increased more pronounced during 1991-2017 and decreased more pronounced during 1951-1970. The precipitation exhibited a fluctuant change from increase to decrease, then increase to decrease and finally increase trends, and there was an abrupt change point in 1965. The annual precipitation had statistically significant cycles of 3-5 year and 7-10 year at 5% significance level. The large-scale teleconnection indices affected the precipitation in Xi'an city. The phase differences between precipitation and teleconnection indices including AO and SOI were in-phase dominated, and anti-phase dominated between precipitation and teleconnection indices including ENSO and sunspot, indicating that the AO and SOI exerted positive climate impacts on the precipitation and vice-versa for ENSO and sunspot.

Assessing Urban Areas’ Vulnerability to Flood Disaster Based on Text Data: A Case Study in Zhengzhou City

Confronting the frequent flood disasters triggered by torrential downpour, the vulnerability of urban rainstorm flood disasters was analyzed with one highly popular area of research in mind: big data. Web crawler technology was used to extract text information related to floods from Internet and popular social media platforms. Combining these text data with traditional statistical data, a flood disaster vulnerability assessment model based on Analytic Hierarchy Process (AHP) was established to evaluate rainstorm and flood disaster vulnerability, and the spatial distribution characteristics of vulnerability to pluvial flooding were analyzed based on Geographic Information System (GIS). The established model was applied in Zhengzhou, a city that often suffers from heavy rainstorms. The results show that the areas located near downtown Zhengzhou were more vulnerable to rainstorm and flooding than others, and most of the city could be at moderate and high vulnerability. Finally, the waterlogging spots extracted from various sources were used to evaluate the performance of the proposed model. The results show that most of waterlogging spots were located in very-high and high risk zones, while less waterlogging spots were found in districts with low vulnerability, which demonstrates the discriminative power of the established model based on big data sources. This study overcomes limited data in flood disaster vulnerability assessment methods and provides a basis for flood control and management in cities.

Seasonal variation and spatial transport of polycyclic aromatic hydrocarbons in water of the subtropical Jiulong River watershed and estuary, Southeast China

Riverine runoff is one of the most important pathways of pollutants entering the oceans. To study the seasonal variations, spatial transports, sources and mass fluxes of polycyclic aromatic hydrocarbons (PAHs) from the subtropical Jiulong River watershed to estuary, water samples were collected in wet and dry seasons. PAH concentrations showed significant temporal-spatial variations (ANOVA, p < 0.05). In the watershed, PAH concentrations in wet season (48.6 ± 18.2 ng L−1) were significantly lower than in dry season (90.3 ± 18.5 ng L−1). In contrast, estuarine PAH concentrations in wet season (67.1 ± 24.6 ng L−1) were significantly higher than in dry season (27.4 ± 10.6 ng L−1) (p < 0.0001). The spatial variations of PAH concentrations in wet and dry seasons reflected positive and restricted transport processes occurred in the river. These findings might be subjected to seasonal changes in precipitation, water discharge, hydrodynamic conditions, and human activities. The compositional patterns of PAHs illustrated that fluorene and phenanthrene were the dominant compounds in the watershed, while phenanthrene was predominant in the estuary. Source analysis by molecular diagnostic ratios and PMF model indicated that fossil fuel and biomass combustion and petroleum both contributed to the presence of PAHs, and the high contributions of pyrogenic PAHs might be related to urban rainstorm runoff in winter and atmospheric inputs in winter. Although the estimated flux of PAHs from watershed to estuary was about 676 kg yr−1 with a low level by comparing the data obtained in the worldwide, continue concern of PAHs in the Jiulong River is recommended due to the intense human activities.

Simulation of Urban Rainstorm Waterlogging and Pipeline Network Drainage Process Based on SWMM

Urban flood has already become weaknesses of flood control system in China. Flood and pipeline drainage calculation based on hydraulics model plays a key role in flood monitoring, warning and control management. On the basis of the topographic maps (high-precision DEM), underground drainage networks, land use and rainfall data in Enshi City, a SWMM-based urban flood model is constructed, which is applied to calculating rainstorm waterlogging and pipeline drainage process under the designed storm probability of 0.01, 0.02 and 0.05, and the designed storm period of 1 hour and 3 hours. The pipeline drainage peak flow of different pipeline type is also retrieved. And results suggest that SWMM is a reliable urban storm water model, which is suitable for urban storm flood simulation and pipeline network drainage analysis.

A Simple GIS-Based Model for Urban Rainstorm Inundation Simulation

With rapid urbanization, floods that occur are more frequently associated with non-riverine, urban flooding. Reliable and efficient simulation of rainstorm inundation in an urban environment is profound for risk analysis and sustainable development. Although sophisticated hydrodynamic models are now available to simulate the urban flooding processes with a high accuracy, the complexity and heavy computation requirement render these models difficult to apply. Moreover, a large number of input data describing the complex urban underlying surfaces is required to setup the models, which are typically unavailable in reality. In this paper, a simple and efficient urban rainstorm inundation simulation method, named URIS, was developed based on a geographic information system (GIS) with limited input data. The URIS method is a simplified distributed hydrological model, integrating three components of the soil conservation service (SCS) module, surface flow module, and drainage flow module. Cumulative rainfall-runoff, output from the SCS model, feeds the surface flow model, while the drainage flow module is an important waterlogging mitigation measure. The central urban area of Shanghai in China was selected as a study case to calibrate and verify the method. It was demonstrated that the URIS is capable of characterizing the spatiotemporal dynamic processes of urban inundation and drainage under a range of scenarios, such as different rainstorm patterns with varying return periods and different alterations of drainage diameters. URIS is therefore characterized with high efficiency, reasonable data input, and low hardware requirements and should be an alternative to hydrodynamic models. It is useful for urgent urban flood inundation estimation and is applicable for other cities in supporting emergency rescue and sustainable urban planning.

A methodology for simple 2-D inundation analysis in urban area using SWMM and GIS

Urban waterlogging occurred frequently in recent years, causing serious social harms and huge economic losses. Accurate waterlogging warning is important for disaster prevention and mitigation. Urban rainstorm waterlogging processing based on Geographic Information System (GIS) and Storm Water Management Model (SWMM) can provide prediction and management of flood situation, but the previous methods of catchments from a single aspect of hydrology or geometry cannot reflect the dual impact of pipe networks and terrain to drainage, and the available inundation algorithms achieved some unreasonable results due to the artificial boundaries. In this paper, a methodology for simple 2-D inundation analysis in urban area using SWMM and GIS is introduced, which need not edit SWMM’s original code. Furthermore, a geometric method of catchments division and inundation algorithm are proposed to improve accuracy. The revised catchments division method provides a good result of supplementing the drainage of terrain, and the improved inundation algorithm can obtain a reasonable inundation distribution based on the principle of source diffusion and dynamic distribution without any boundary limit. The case study was performed in Longwen District of Zhangzhou, and good results are achieved: (1) The external outflow percentage of the revise method is always bigger than that of the geometric method, and the value of the revised method is 25.18%, while that of geometric method is only 19.56% at rainfall peak, and (2) the less the rainfall is, the less grids flooded in two algorithms there are with only 14.30% when the rainfall is 0.1 mm.

Spatiotemporal Variance Assessment of Urban Rainstorm Waterlogging Affected by Impervious Surface Expansion: A Case Study of Guangzhou, China

Urban rainstorm waterlogging has become a typical “city disease” in China. It can result in a huge loss of social economy and personal property, accordingly hindering the sustainable development of a city. Impervious surface expansion, especially the irregular spatial pattern of impervious surfaces, derived from rapid urbanization processes has been proven to be one of the main influential factors behind urban waterlogging. Therefore, optimizing the spatial pattern of impervious surfaces through urban renewal is an effective channel through which to attenuate urban waterlogging risk for developed urban areas. However, the most important step for the optimization of the spatial pattern of impervious surfaces is to understand the mechanism of the impact of urbanization processes, especially the spatiotemporal pattern of impervious surfaces, on urban waterlogging. This research aims to elucidate the mechanism of urbanization’s impact on waterlogging by analysing the spatiotemporal characteristics and variance of urban waterlogging affected by urban impervious surfaces in a case study of Guangzhou in China. First, the study area was divided into runoff plots by means of the hydrologic analysis method, based on which the analysis of spatiotemporal variance was carried out. Then, due to the heterogeneity of urban impervious surface effects on waterlogging, a geographically weighted regression (GWR) model was utilized to assess the spatiotemporal variance of the impact of impervious surface expansion on urban rainstorm waterlogging during the period from the 1990s to the 2010s. The results reveal that urban rainstorm waterlogging significantly expanded in a dense and circular layer surrounding the city centre, similar to the impervious surface expansion affected by urbanization policies. Taking the urban runoff plot as the research unit, GWR has achieved a good modelling effect for urban storm waterlogging. The results show that the impervious surfaces in the runoff plots of the southeastern part of Yuexiu, the southern part of Tianhe and the western part of Haizhu, which have experienced major urban engineering construction, have the strongest correlation with urban rainstorm waterlogging. However, for different runoff plots, the impact of impervious surfaces on urban waterlogging is quite different, as there exist other influence factors in the various runoff plots, although the impervious surface is one of the main factors. This result means that urban renewal strategy to optimize the spatial pattern of impervious surfaces for urban rainstorm waterlogging prevention and control should be different for different runoff plots. The results of the GWR model analysis can provide useful information for urban renewal strategy-making.

An Emergency Decision-Making Method for Urban Rainstorm Water-Logging: A China Study

With the rapid development of the urbanization process, rainstorm water-logging events occur more frequently in big cities in China, which causes great impact on urban traffic safety and brings about severe economic losses. Water-logging has become a hot issue of widespread concern in China. As one kind of natural disasters and emergencies, rainstorm water-logging has the uncertainties of occurrence, development, and evolution. Thus, the emergency decision-making in rainstorm water-logging should be carried out in stages according to its development trend, which is very complicated. In this paper, an emergency decision-making method was proposed for urban water-logging with a hybrid use of dynamic network game technology, Bayesian analysis, and multi-attribute utility theory. The dynamic game process between “rainstorm water-logging” and “decision-making group” was established and the dynamic generation of emergency schemes was analyzed based on Bayesian analysis in various stages of water-logging. In terms of decision-making attributes, this paper mainly considered two goals, i.e., ensuring smooth traffic and controlling emergency cost. The multi-attribute utility theory was used to select the final scheme. An example analysis in Guangzhou of China showed that the method is more targeted and can achieve emergency management objectives more effectively when compared with traditional methods. Therefore, it can provide reference for the scientific decision-making of emergency management in urban rainstorm water-logging.

Real-time identification of urban rainstorm waterlogging disasters based on Weibo big data

With the acceleration of urbanisation in China, preventing and reducing the economic losses and casualties caused by urban rainstorm waterlogging disasters have become a critical and difficult issue that the government is concerned about. As urban storms are sudden, clustered, continuous, and cause huge economic losses, it is difficult to conduct emergency management. Developing a more scientific method for real-time disaster identification will help prevent losses over time. Examining social media big data is a feasible method for obtaining on-site disaster data and carrying out disaster risk assessments. This paper presents a real-time identification method for urban-storm disasters using Weibo data. Taking the June 2016 heavy rainstorm in Nanjing as an example, the obtained Weibo data are divided into eight parts for the training data set and two parts for the testing data set. It then performs text pre-processing using the Jieba segmentation module for word segmentation. Then, the term frequency–inverse document frequency method is used to calculate the feature items weights and extract the features. Hashing algorithms are introduced for processing high-dimensional sparse vector matrices. Finally, the naive Bayes, support vector machine, and random forest text classification algorithms are used to train the model, and a test set sample is introduced for testing the model to select the optimal classification algorithm. The experiments showed that the naive Bayes algorithm had the highest macro-average accuracy.

Up-to-date urban rainstorm intensity formulas considering spatial diversity in China

With accelerating urbanization in China, urban waterlogging has had a serious impact on urban sustainable development and citizen welfare. Simple urban rainstorm intensity formulas with a monotonous frequency distribution type cannot meet the practical needs of urban drainage planning and design. This study focuses on the development of urban rainstorm intensity formulas based on spatial diversity in China. Using the annual maximum sampling method, rainstorm data of 607 cities throughout China were collected into a database, with a total of 24,933 rainfall samples (annual observations) under various specified precipitation durations. The database was used to verify that integrating the Pearson III and Gumbel distributions would constitute an optimal theoretical distribution type, owing to its small error and increased fitting precision. Modification and coordination of four important parameters in the rainstorm intensity formula were done using a digital elevation model, which improved the accuracy of the formula. In addition, precipitation distributions in China were treated from the perspective of topographic features to validate the calculations from up-to-date formulas. Accuracy assessment was accomplished using a national code (GB-50014-2006), GIS-based isograms, and authoritative results from the Hydrological Bureau of the Ministry of Water Resources. This work provides a comprehensive foundation for the establishment of an up-to-date rainstorm intensity formula for China, which can be used widely in different cities.

Study on the Runoff Simulation of Urban Rainstorm Based on SCS Model

Rainstorms have been frequently occurred and caused serious urban waterlogging disaster in China recent years. A runoff simulation method has been explored based on the rainfall intensity formula, as well as the combination of Chicago Rainfall Process Line Formula and SCS model in this paper. Because of its heavy rainstorm, Tangxunhulake basin in Wuhan was selected as the study area and to simulate the runoff process in different return periods. The results show that the cumulative runoff ranges from 22.3 to 45.3 million m3, and the net increased storage volume ranges from 10.02to 32.87 million m3; the return flow period of more than 20 years would affect the surrounding urban areas and cause damage to some extent. The proposed method of this study is simple and reliable, and can provide a great reference for the waterlogging calculation in urban areas.

Finding of urban rainstorm and waterlogging disasters based on microblogging data and the location-routing problem model of urban emergency logistics

Due to the climate change and the rapid progress of urbanization, extreme weather disasters such as urban rainstorm and waterlogging are frequent. Therefore, how to find the waterlogging points in the presence of disasters and how to optimize the distribution of urban emergency logistics and reduce the negative impact of disasters have become a hot and difficult issue for government departments and scholars. First of all, the idea and method of using the big data of microblogging to obtain urban rainstorm and waterlogging disasters and public sentiment are put forward. In addition,this thesis constructed the location-routing problem model of urban emergency logistics in the situation of rainstorm and waterlogging disaster, and found out the dynamic emergency distribution path of Nanjing in the situation of waterlogging disaster by using NSGA-III algorithm. Research shows that the risk management of urban rainstorm and waterlogging disasters, together with social media data, is a feasible way to obtain on-site data of disasters and carry out risk assessment of disasters. At the same time, the emergency logistics location-positioning model and algorithm can provide a reference for similar disaster emergency logistics distribution network and the conclusion can provide empirical reference for cities to cope with rainstorm and waterlogging disasters.

Multivariate frequency analysis of urban rainfall characteristics using three-dimensional copulas

Urban runoff is a major cause of urban flooding and is difficult to monitor in the long term. In contrast, long term continuous rainfall data are generally available for any given region. As a result, it has become customary to use design rainfall depth as a proxy for runoff in urban hydrological analyses, with an assumption of the same frequency for runoff and rainfall. However, this approach has lack of overall coordination and cannot fully reflect the variability of rainfall characteristics. To address this issue, this study presents a three-dimensional copula-based multivariate frequency analysis of rainfall characteristics based on a long term (1961-2012) rainfall data from Guangzhou, China. Firstly, continuous rainfall data were divided into individual rainfall events using the rainfall intensity method. Then the characteristic variables of rainfall (design rainfall depth, DRD; total rainfall depth, TRD; peak rainfall depth, PRD) were sampled using the annual maximum method. Finally, a copula method was used to develop the multivariate joint probability distribution and the conditional probability distribution of rainfall characteristics. The results showed that the copula-based method is easy to implement and can better reflect urban rainstorm characteristics. It can serve a scientific reference for urban flood control and drainage planning.

Simulation of the hydrological and environmental effects of a sponge city based on MIKE FLOOD

Based on the pilot area of a sponge city in Northwest China, the MIKE FLOOD models of urban flood and nonpoint source pollution are established. The uncertainty analysis of model shows that such parameters as hydrological reduction factor, imperviousness, and decay constant have big influences on the total runoff, peak flow, and water quality. The measured data of the rainfall events 20160724 and 20160623 are used to calibrate and validate the model. The correlation coefficients (R 2 ) and Nash–Sutcliffe efficiency coefficient (Ens) are both over 0.65. The changes in urban rainwater runoff and water quality for different rainfall conditions under traditional development (TD) and low impact development (LID) modes are simulated. The results show that: (1) Compared with TD mode, for different rainfall conditions under LID mode, the reduction rates of overflow and the overload pipes are, respectively, 22.4–100 and 0–54.55% when the area proportion of LID measures is 17.76%. The total runoff reduction rate is 64.01–81.52%, the peak flow reduction rate is 0–69.09%, and the flood peak time is delayed by 0–48 min. (2) Compared with TD mode, after adding LID measures, the load reduction rates of total suspended solids (SS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) are increased by 19.20–68.71, 19.19–67.78, 18.72–60.91, and 19.89–68.75%, respectively. The effluent reduction rates of the event mean concentrations (EMCs) of SS, COD, TN, and TP are increased by 0.65–42.07, 0.65–40.34, 0.06–27.62, and 1.51–42.14%, respectively. (3) The LID measures have certain control on waterlogging situation, and the submerged area under different water depths and flooding durations are decreased by 11.11–100 and 32.23–100%, respectively. For 19.2 mm rainfall event, under the LID mode, the SS load reduction rate achieves 60%, and rainfall runoff is all assimilated without discharge and waterlogging phenomena. LID measures have a better control effect on water quality and water quantity of urban rainstorm runoff; however, the effect of LID measures will reduce with the increase in recurrence interval.

An urban pluvial flood simulation model based on diffusive wave approximation of shallow water equations

Abstract Urban floods caused by sudden heavy rainstorms are becoming more frequent and causing serious problems in many cities. Developing methods to simulate urban rainstorm floods is helpful in disaster prevention and mitigation. In this paper, we establish an urban pluvial flood simulation model based on diffusion wave approximation of shallow-water equations. The model takes full account of the characteristics in urban pluvial floods, and includes many improvements in simulation details. These details include building a consideration method, a rainfall consideration method, and so on. A new calculation method of water surface gradient is established, which is suitable for complex topology in urban pluvial flood simulation and can reduce unnecessary simulation error introduced by calculation methods. The accuracy and stability of the model are verified through simple cases with analytical solution and experiments with measured data. The results show that the new model is more accurate than common diffusion wave approximation models. A new treatment to avoid ‘checkerboard oscillation’ is established. In comparison with existing methods, the new method proved to be the best. A proof of concept shows that the new model can deal with complex situations and is helpful for urban drainage system planning.

城市暴雨强度公式编制与分析研究

为提高城市防洪能力，防控城市内涝，用近年长系列有代表性的可靠的降雨资料，建立符合当地客观实际的城市暴雨强度公式，并籍此计算相应较高标准的设计暴雨强度和设计流量。本文以黄山市为例，研究了城市暴雨频率p-III型分布参数的推求和建立暴雨公式方法及年次频率的转换。论证了城市暴雨公式的频率分布是p-III型分布α = 1或Cs = 2时的特例，形式简单，仅两个参数，从而提出频率曲线的适线技巧，操作更加方便，并按照超定量系列的分布趋势，分段适线，对各历时的频率曲线进行了平衡协调等，使频率曲线更为合理，精度更高，误差更小。同时介绍了Cv值的调整与计算方法及年多个样法的频率转换公式，并进行优越性评价与比较。 In order to improve the urban flood control capacity and prevent urban waterlogging, typical and reliable rainfall data collected in recent years are analyzed to set up an urban rainstorm intensity formula in accordance with the practical situation and on which the calculation of a comparatively high standard storm intensity and design water flow is based. Taking Huangshan City as an example, the paper calculates the urban rainstorm frequency distribution model of p-III type parameters and establishes rain- storm formula method and frequency conversion in frequency and time. It demonstrates that the frequency distribution of urban rainstorm formula is a special case of p-III distribution when α = 1 or Cs = 2. The frequency distribution has a simple form, only two parameters. And then the frequency curve line technique is put forward, operating more convenient. According to the distribution trend of super quantitative series, piecewise line, frequency curve of the last balance coordination, etc., the frequency curve with higher precision, less error is more reasonable. Meanwhile, the adjustment and calculation of Cv and yearly multiple frequency conversion formula are mentioned, so as to evaluate and compare the corresponding advantages and disadvantages.