Numerical modeling of dam-break flood through intricate city layouts including underground spaces using GPU-based SPH method

This paper applies the meshfree Smoothed Particle Hydrodynamics （SPH） method with Graphical Processing Unit （GPU） parallel computing technique to investigate the highly complex 3-D dam-break flow in urban areas including underground spaces. Taking the advantage of GPUs parallel computing techniques, simulations involving more than 107 particles can be achieved. We use a virtual geometric plane boundary to handle the outermost solid wall in order to save considerable video card memory for the GPU computing. To evaluate the accuracy of the new GPU-based SPH model, qualitative and quantitative comparison to a real flooding experiment is performed and the results of a numerical model based on Shallow Water Equations （SWEs） is given with good accuracy. With the new GPU-based SPH model, the effects of the building layouts and underground spaces on the propagation of dambreak flood through an intricate city layout are examined.     

Prediction of the future flood severity in plain river network region based on numerical model: A case study

Suzhou is one of China's most developed regions, located in the eastern part of the Yangtze Delta. Due to its location and river features, it may at a high risk of flood under the climate change background in the future. In order to investigate the flood response to the extreme scenario in this region, 1-D hydrodynamic model with real-time operations of sluices and pumps is established. The rain-runoff processes of the urban and rural areas are simulated by two lumped hydrologic models, respectively. Indicators for a quantitative assessment of the flood severity in this region are proposed. The results indicate that the existing flood control system could prevent the Suzhou Downtown from inundation in the future. The difficulty of draining the Taihu Lake floods should be given attention to avoid the flood hazard. The modelling approach based on the in-bank model and the evaluation parameters could be effective for the flood severity estimation in the plain river network catchment. The insights from this study of the possible future extreme flood events may assist the policy making and the flood control planning.     

基于多类模型耦合的城市洪水风险 分析技术研究

基于城市洪水的特点,提出了简化的城市排水模型,并与SCS水文模型和二维浅水动力模型相耦合,建立了城市洪水风险分析模型。该模型能够模拟城市外洪、内涝或二者的组合,并以蚌埠市为例,开展示范研究,计算结果与实际情况相符,证明了模型的适用性.     

城市内涝灾害居民出行困难度评价

城市内涝灾害给城市居民生命、财产安全造成了严重威胁。以长春市南关区为例,以二维非定恒定流为基本骨架,以不规则网格概化地形,用一维非恒定流描述排水管网,建立了城市暴雨内涝数值模型。该模型包含产流模型、汇流模型、排水模型及内涝模型。以30 a,50 a,100 a一遇的暴雨情景,对居民出行困难度进行了评价。验证结果表明,构建模型与实例结果吻合度较高。所得结果可为相关部门采取应急措施缓解内涝导致的交通堵塞提供参考。     

防洪排涝排水一体化模型在洪水风险图编制中的应用

随着城市洪涝灾害频繁发生,编制洪水风险图已成为当前国内外城市防洪减灾工作中重要内容,它可反映区域洪涝成因、量级、特性、危及对象及应急对策等风险信息分布特征。采用水力学方法构建水力学模型模拟研究区域洪水演进情况是洪水风险图编制常用的方法,通过构建考虑河道、城市地下管网、排水系统设施、阻水建筑物、水利工程及调度的防洪排涝排水一体化模型,将城市防洪排涝与排水有机结合,并兼顾流域与区域风险,通过历史降雨对模型进行校核验证,保证模型的可靠性。模拟计算了景德镇市城区因超标准洪水导致防洪墙溃决或城市暴雨可能发生的受淹和积水情况,并根据计算结果绘制洪水风险图,对景德镇市预防外围洪水、降低城市内涝洪水影响及土地利用和城市发展规划等提供决策依据和技术支持。     

日本城市防洪减灾综合措施及发展动态

简介日本城市防洪减灾体系的形成和发展过程。认为日本城市防洪减灾体系的形成争发展与日本社会经济的发展密切相关,经济发展为提高防灾能力提供了物质保障,而社会防灾能力的提高既促进了流域土地开发利用,又对防洪体系提出了更高的要求。从修建水库、整治河道、开挖地下河流、建设滞洪区和排涝泵站4个方面阐述日本城市治水的主要工程措施;从提高洪水预测预报水平、提高险情信息传达速度、提高全民防灾意识、制作“可能受灾区域的洪水险情图”、进行重要城市中小河流的洪水预报5个方面阐述日本采取的减轻城市水灾的主要对策。介绍了日本的3个防汛救灾组织:消防部门,防汛团和防汛事务组织,救援自卫队。近年来发生在城市的河流洪水灾害对日本城市防洪体系提出了新的课题,使日本防洪体系向灾害防止兼顾灾害减轻的方向发展;在传统的防洪工程措施的基础上,日本正在研究制定个人、地方和国家共同发挥作用的防洪减灾体系。     

Recent Flood Control Measures for Urban Rivers in Japan: Case Study of the Kanda River in Tokyo

ABSTRACT

Recently, floods occurred frequently almost everywhere in urban areas in Japan. These urban disasters became an important social problem. In the present study, we investigated floods on the Kanda River in Tokyo. The history of flooded areas, and flood control projects in progress, involving river improvements, expansion of sewerage projects, and urbanization, are reviewed. We also have presented our recent survey results for the flood of August 27, 1993 that occurred in the Kanda River Basin. Hydraulic and hydrologic impacts of historical floods are also given, including an investigation of the economic and social impacts. In urban areas, it is difficult to increase the width of the river. Thus, river improvement works essentially consist of the use of underground diversion channels. In Tokyo, Takadanobaba, Edogawabashi, and Suidobashi diversion channels have been completed. Regulating reservoirs along these rivercourses have been constructed in the Myoshoji River Basin and Zenpukuji River Basin. It is quite difficult to buy land along river courses in Japan. An interesting decision was recently made about the 75mm Plan, which introduces a new method for an underground river; the so-called Tokyo Loop 7. The underground river consists of a pipe having a diameter of 10.0–12.5 m. Loop 7 starts from the upstream section of the Shirako River; and draws flood water from ten different rivers, including the Myoshoji, Zenpukuji, and Kanda rivers. The total length of the pipe is 30 km. The flood water through Loop 7 is pumped out to Tokyo Bay.     

尾闾河段的数值模拟研究

尾闾河段是否畅通，直接关系到河流能否安全泄洪、排沥，是水利部门十分关注的问题。本文阐述了采用一、二维耦合数学模型进行尾闾河段洪水与潮波的模拟的基本理论，对耦合模型的交界面条件及耦合方式进行了详细说明，并以某河尾闾段为例建立一、二维耦合模型。一维数学模型研究计算的范围为河口区上游的河段，平面二维数学模型研究计算的范围为近挡潮闸河段以及至河口外近海区域。模型以历史洪水和实测潮波分别进行了验证，计算结果与观测结果吻合良好，表明耦合模型可以较好地反映模拟河段及近海区的洪水与潮汐特性，解决河流尾闾段的水力模拟计算。     

REAL-TIME FLOOD FORECASTING METHOD WITH 1-D UNSTEADY FLOW MODEL

A real-time forecasting method coupled with the 1-D unsteady flow model with the recursive least-square method was developed. The 1-D unsteady flow model was modified by using the time-variant parameter and revising it dynamically through introducing a variable weighted forgetting factor,such that the output of the model could be adjusted for the real time forecasting of floods. The application of the new real time forecasting model in the reach from Yichang to Luoshan of the Yangtze River was demonstrated. Computational result shows that the forecasting accuracy of the new model is much higher than that of the original 1-D unsteady flow model. The method developed is effective for flood forecasting,and can be used for practical operation in the flood forecasting.     

广西防汛三维电子沙盘系统建设

广西防汛三维电子沙盘系统利用现代高新信息技术,模拟建设了广西全区及重点河段的三维空间场景,展示流域地形地貌、防洪工程、山洪灾害易发区分布等防汛信息;并在三维场景中实现洪水淹没快速评估、山洪灾害快速定位、山洪灾害影响分析等内容,为广西各级防汛部门的防洪减灾决策提供技术支持。     

涪江通口河流域河网提取及唐家山溃流洪水模拟分析

基于美国Global Land Cover Facility（GLCF）的2004．3 Arc Second SRTM Elevation全球90m精度的DEM数据源,采用作者开发的DEM凹陷区域识别与处理、河网自动生成与流域划分软件,提取了四川省唐家山堰塞湖所在涪江通口河流域河网相关信息。采用具有高分辨率及高稳定性能格式精度的二维水动力学模型,将两种估算的唐家山堰塞湖溃决流量过程作为输入,估算了唐家山堰塞湖以下涪江通口河流域的洪水过程与低洼地的洪水淹没过程。结果表明,从公开的高分辨率全球DEM数据自动提取指定流域信息,采用二维水动力学模型模拟流域尺度突发洪水淹没过程的模型系统,可以快速、便捷地模拟不同流域的洪水演进过程,可为国家的洪水灾害防治分析提供实用和可靠的技术工具和手段。     

“2D城市洪涝与流域汛情风险预警评估系统”应用探讨

城市洪涝预警预报对保障城市正常运转意义重大。为有效地提升洪涝预警评估水平,有必要借鉴国外的先进方法与技术。"2D城市洪涝与流域汛情风险预警评估系统(FRMFS)"在技术上属国际先进水平,浙江省引进后,结合实际进行消化、吸收、二次开发,从数据采集、预报模型等方面验证了其在中小城市中的适用性。实例成果表明该系统对有效提升城市防汛抗灾综合能力具有实际意义。     

Low Impact Development Measures Spatial Arrangement for Urban Flood Mitigation: An Exploratory Optimal Framework based on Source Tracking

Urban areas are vulnerable to flooding as a result of climate change and rapid urbanization and thus flood losses are becoming increasingly severe. Low impact development (LID) measures are a storm management technique designed for controlling runoff in urban areas, which is critical for solving urban flood hazard. Therefore, this study developed an exploratory simulation–optimization framework for the spatial arrangement of LID measures. The proposed framework begins by applying a numerical model to simulate hydrological and hydrodynamic processes during a storm event, and the urban flood model coupled with the source tracking method was then used to identify the flood source areas. Next, based on source tracking data, the LID investment in each catchment was determined using the inundation volume contribution ratio of the flood source area (where most of the investment is required) to the flood hazard area (where most of the flooding occurs). Finally, the resiliency and sustainability of different LID scenarios were evaluated using several different storm events in order to provide suggestions for flooding prediction and the decision-making process. The results of this study emphasized the importance of flood source control. Furthermore, to quantitatively evaluate the impact of inundation volume transport between catchments on the effectiveness of LID measures, a regional relevance index (RI) was proposed to analyze the spatial connectivity between different regions. The simulation–optimization framework was applied to Haikou City, China, wherein the results indicated that LID measures in a spatial arrangement based on the source tracking method are a robust and resilient solution to flood mitigation. This study demonstrates the novelty of combining the source tracking method and highlights the spatial connectivity between flood source areas and flood hazard areas.

     

基于城市雨洪模型的市政排水与水利排涝标准衔接研究

针对目前存在的市政排水与水利排涝两个标准的衔接仍无规范统一方法的问题,以广州市东濠涌流域为研究区域,采用城市综合流域排水模型Info Works ICM建立东濠涌流域管道、河道及地面二维耦合模型,分析计算市政排水1年一遇与水利排涝5年一遇以及市政排水1年一遇与水利排涝10年一遇两种情况下的标准衔接关系,为城市排水防涝规划设计提供技术支撑。结果表明:1年一遇市政排水标准与10年一遇水利排涝标准的组合能够满足流域涝水顺利排除的要求,但管道排水口底高程距河底高程的距离过短也会对管道的水位顶托产生一定影响,故建议城市排水管网的规划建设应至少保证排水口底高程高于河道底高程0.5 m以上。     

城市雨洪排涝计算模型研究

城市街道积水回流对地下管网排水影响显著,为了反映地表回流的影响,提出了包含街道和管道的双层排水结构模型,通过虚拟连接通道进行地表和地下排水系统的水量交换,并推导了通道过流量的计算方法,实现了街道积水回流的模拟,建立了完整的城市雨洪排涝计算模型。利用典型案例对模型计算进行验证,结果表明:该模型可模拟街面积水和过流过程,在发生街道漫流的情况下,计算结果合理,较传统模拟方法更贴近实际。     

排水体系建设对城市洪涝灾害的影响

地下管网、水系等是城市重要的排水体系,直接决定着城市的洪涝安全。以武汉市光谷中心城为研究区域,采用一、二维耦合的水动力数学模型,进行了不同排水体系组合条件下的多方案城市雨洪模拟,量化分析了地下管网、规划水系建设对城市洪涝灾害的消减效果。结果表明:光谷中心城现状未形成成熟排水体系时,其内涝范围、淹没面积及受灾损失均最大,规划排水体系建设后,区域洪涝淹没面积和受灾损失消减率分别达56.58%,63.74%。由于作用范围及作用方式不同,单独建设水系对区域排涝的作用低于单独建设地下管网的作用。对不同土地利用类型比较,住宅用地减灾效果对城市排水体系的建设最为敏感。当下游湖泊水位较高时,湖泊对水系存在顶托作用,其对区域洪涝灾害影响的程度与河道纵向比降、河堤高程,以及地下管网和河道的连接状况有关。     

一维溃坝波在斜底坡河道中演进的解析解

应用特征线理论建立了一维瞬时全溃洪水在下游无水、斜底、梯形河道中演进的解析模型,结果显示Ritter解为本文模型在平坡底、矩形断面河道下的一个特解。依据导出的解析模型,对河道底坡的影响进行了分析计算,表明正坡会加速溃坝洪水的演进而逆坡有阻滞作用,而且这种底坡促流或阻流效应具有随时间增长的特点。     

溃口近区二维数值模拟与溃坝洪水演进耦合

基于黏土心墙砂石坝的溃决过程,以及溃坝洪水传播和运动的特性,建立黑河金盆水库大坝溃口近区二维数值模型和下游地区溃坝洪水演进耦合数学模型。使用DAMBRK法计算逐渐溃坝,并应用其结果进行后续模拟。采用Abbott-Ionescu六点隐式有限差分格式求解一维模型,采用单元中心的有限体积法求解二维模型方程。采用侧向连接方式,将黑河两岸计算水位点与二维网格单元相连,实现一、二维模型的耦合。采用所建立的二维模型对溃口近区进行计算与模拟,得到计算区域某一时刻的水深及流速分布。应用所建耦合模型对黑河金盆水库万年一遇入库洪水漫顶致溃坝洪水进行数值模拟,得到一维河道内各断面的水位和流量变化过程,以及二维计算区域内不同时刻的水深分布图、流速矢量图和淹没范围变化过程。溃口的形成过程不仅包括漫顶水流的直接作用,同时包括溃口形成过程中两侧漩涡状水流的反冲刷作用。耦合模型可以同时兼顾河道内的水流变化以及河道外计算区域内的洪水演进过程,从而减少由于计算结果偏大或偏小所带来的防洪资源浪费和防洪措施不利等不良影响。     

蓄滞洪区洪水演进模拟

系统地研究了描述洪水在蓄滞洪区内演进过程的一不恒定流模型和二维流模型，突出对河流与沿河堤外洼地间水流交换的描述和对淹没区各蓄水单元间水流交换的描述及河流与调蓄区水流连接的描述，最后简要介绍了实例。     

一维洪水数值模拟技术在流域防洪规划中的应用

南美洲厄瓜多尔境内的Guayas河流域中下游社会经济发达,但洪水问题突出,是该国流域综合规划的防洪重点地区。通过综合规划论证,拟兴建由堤防、水库、蓄滞洪区、分洪道和挡潮闸组成的防洪工程体系。基于MIKE11软件平台构建了Guayas河流域中下游河网洪水一维数值模型,对平原感潮河网的洪水演进规律和规划的防洪工程体系联合运用进行了模拟计算。在模拟中,通过合理概化河网、优化河道断面布置,以及采用堰闸过流公式代替圣维南方程作为堰闸工程所在断面的水流运动方程,有效避免数值振荡问题。在模拟结果的基础上拟定了洪水安排方案和防洪工程规模。