Exposure assessment of rainstorm waterlogging on old-style residences in Shanghai based on scenario simulation

Waterlogging is one of the most serious hazards in China. Old-style residences in cities are prone to be damaged by waterlogging hazards. This paper describes our exposure assessment of old-style residences in Shanghai during rainstorm waterlogging. Two rainstorm scenarios of 20-year and 50-year return periods were simulated with the rainstorm simulation model from Shanghai Flood Risk Information Center. Each old-style residence was ranked according to its degree of exposure indicated by the inundation depth of that residence. An exposure assessment model was then built to integrate three ranks of exposure in order to reflect the total exposure features of a district and to compare disaster situation among different districts. Our research results reveal that Hongkou District and Huangpu District are the regions most necessary for the government to carry out safety defense in old-style residences, while rainstorms bring little effect on old-style residences in the districts of Putuo, Luwan, Changning, Zhabei, and Jing’an. These results provide important information for Shanghai Municipal Government to improve waterlogging management, and the method of exposure assessment can also be applied in other cities to provide guidance regarding flood risk control.     

Rainstorm waterlogging risk assessment in central urban area of Shanghai based on multiple scenario simulation

With the acceleration of the urbanization process, waterlogging problems in coastal cities are becoming more and more serious due to climate change. However, up until now, the common procedures and programs for rainstorm waterlogging risk assessment in coastal cities still have not formed. Considering a series of impact factors of rainstorm waterlogging in coastal city, the present study established a paradigm for rainstorm waterlogging risk assessment through the combination of hydrological modeling and GIS spatial analysis, and took the residence in central urban area of Shanghai as an example. First, the simplified urban waterlogging model was applied to simulate the depth and extent of rainstorm waterlogging under six hypothetic scenarios. Second, the residence exposed to rainstorm waterlogging was extracted and analyzed supported by spatial analysis module of ArcGIS. Then, stage-damage curves were applied to analyze the loss rate of structure and contents of residential building. Finally, the waterlogging loss maps of residence in different scenarios, the annual average loss, and the risk curve were taken as the expression of waterlogging risk. The results show that the inundated water depth, vulnerability, and losses of residence all increase as the intensity of rainstorm increases. The old-style residence is most vulnerable to rainstorm waterlogging, followed by the new-style residence, and villa is less vulnerable to rainstorm waterlogging. The annual average loss of residence in Shanghai central urban area was about CNY 22.25 million. The results also indicate high risk in Yangpu and Putuo districts, Xuhui, Hongkou, Changning and Zhabei districts come under medium-risk zone, and Jing’an, Luwan and Huangpu districts come under low-risk zone. These results provide important information for the local government, and the methodology can be applied in other cities to provide guidance on waterlogging risk governance.     

Population vulnerability assessment based on scenario simulation of rainstorm-induced waterlogging: a case study of Xuhui District, Shanghai City

Waterlogging is one of the most serious hazards in cities. People are the core of the human social system and the main group affected by disasters. This research introduces a method of scenario simulation which provides a basis for the accurate measurement of exposure to waterlogging. Then based on the concept and structure of vulnerability, representative indicators are selected to develop an indicator system based on objective weights derived from principal components analysis. The method is then used to conduct a population vulnerability assessment in Xuhui District of Shanghai city based on scenario simulation of rainstorm-induced waterlogging over a 50-year period. The final assessment results show that the population vulnerability is greatest for Tianlin Street, Lingyun Street, Changqiao Street, Fenglin Street, and Caohejing Street, while Tianping Street, Xujiahui Street, and Xietulu Street have medium levels of vulnerability. Hongmei Road Street, Healthy Village Street, Longhua Street, and Hunan Road Street have low levels of vulnerability, and Huajing Town is the area with the lowest population vulnerability. The results provide both necessary information and guidance for the government to improve the flood management.     

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.     

Risk assessment of rainstorm and flood disasters in China between 2004 and 2009 based on gray fixed weight cluster analysis

Rainstorm and flood disasters frequently occur in China, causing heavy losses for people’s lives and property and reducing the capability of sustainable development of the national and local economy. In this study, the risks of the rainstorm and flood disasters are assessed for the Chinese mainland, excluding Hong Kong, Macao, and Taiwan and also employ the historical data of seven indicators, including the affected area of crops, the affected population, the direct economic loss, and etc., from 2004 to 2009. Based on the large 1,302 historical sample data, the impact of rainstorm and flood disasters were analyzed using the methodology of gray fixed weight cluster analysis according to disaster losses, which were divided into the three gray classes of high, medium, and low. The regional differences of the risk assessment of the rainstorm and flood disasters are discussed, and the dynamical risk zoning map is conducted. The results show a consistent conclusion with the actual losses of rainstorm and flood disasters over each administrative district, which can provide more scientific evidence for the relevant departments of disaster prevention and mitigation.     

岩溶浸没内涝灾害的物理(数学)模拟研究

红水河梯级水电站的百龙滩、岩滩等库区，由于岩溶地下河系统的存在，在水电站蓄水以前，每逢大雨，就会造成库区谷地的浸没内涝，在水库蓄水以后，由于地下河出口水位的提高，使得库区内涝灾害加重，为了研究库区洼地水库蓄水前、后浸没内涝灾害的规律，根据该地区的水文地质条件，组装了物理模型。采用物理（数学）模拟的方法对红水河百龙滩水电站库区的地苏地下河系统进行模拟计算。研究库区凤翔、镇兴、南江谷地在不同的大气降水、不同的地下河出口水位条件下，谷地的内涝水位的变化规律，建立起3个谷地的数学模型，同时，对可能出现的降雨类型进行模型预测。     

Risk assessment of groundwater pollution using sensitivity analysis and a worst-case scenario analysis

This paper illustrates how sensitivity analysis and a worst-case scenario analysis can be useful tools in risk assessment of groundwater pollution. The approach is applied to a study area in Hungary with several known groundwater pollution sources and nearby drinking water production wells. The main concern is whether the contamination sources threaten the drinking water wells of the area. A groundwater flow and transport model is set up to answer this question. Due to limited data availability, the results of this model are associated with large uncertainty. Sensitivity analysis and a worst-case scenario analysis are applied to estimate this uncertainty and build confidence in the model results.     

Risk mechanisms of large group emergency decision-making based on multi-agent simulation

Natural Hazards - There are many critical sources of risk in large group emergency decision-making. In this paper, we systematically identify individual and group sources of risk in large group...     

基于参数反演的边坡地下水渗流数值模拟

渗流是影响岩土工程边坡稳定性的重要因素,对不同工况下岩土体边坡地下水渗流规律进行数值模拟,弄清其动态变化规律,对于边坡稳定性分析、支护设计、工程防排水措施的制定等都有重要的意义。以龙滩水电站左岸进水口边坡为研究对象,通过免疫进化规划算法,得到了边坡岩体渗流场参数。在此基础上,对洪水期、枯水期情况下地下水渗流状态进行了数值模拟,通过对比分析,研究了不同河床水位情况下地下水渗流变化规律,从而为边坡稳定性预测奠定了理论基础。     

基于区间分析理论的地表沉降风险评价

为解决地表沉降风险的定量评价问题,提出了用区间估计的方法预测地表最大沉降,并在此基础上定义了风险评价指标。利用响应面法对地表最大沉降与地层参数之间的关系进行近似描述,基于区间分析理论确定地表最大沉降的区间范围,可较好考虑参数不确定性对计算结果的影响。以北京某在建车站主体侧洞为例,说明了此方法的适用性。     

福建雨季暴雨及台风暴雨诱发地质灾害的研究

以1990～2006年发生地质灾害为例,运用实证研究法,通过天气、气候学的分析和数理统计处理,揭示了福建重度地质灾害和严重地质灾害的时空分布规律;给出了不同天气系统暴雨所致地质灾害的基础雨量与触发雨量;对比分析了雨季暴雨、台风暴雨诱发严重地质灾害的实例。研究表明,福建地质灾害以滑坡为主(80.5%),崩塌为次(15.5%),泥石流较少(4%)。时空分布特点6月份为高峰期,内陆的南平和三明是频发区,对应天气系统是雨季的梅雨锋;8月份为次峰期,沿海的漳州和泉州是频发区,对应天气系统是台风。地质灾害对暴雨的滞后期,雨季期长,台风期短,其基础雨量台风雨小于锋面雨,而临近触发雨量则相反,台风雨大于锋面雨。     

基于三维数值模拟的露天煤矿复合边坡稳定性分析

借助VC及fish语言编程,将AutoCAD、Surfer、ANSYS等软件耦合应用,完成了复杂地质条件下的FLAC3D建模。在地质调查及统计分析试验数据的基础上,应用Hoek-Brown经验破坏准则确定了边坡岩体的综合强度指标。然后,采用FLAC3D,对比分析了不考虑地下水及三维流固耦合两种情况下的位移场、应力场和塑性区分布规律,并采用强度折减法求得了三维边坡安全稳定系数。结果表明,由外排土场和采掘帮坡构成的复合边坡呈现复杂的潜在破坏模式,以及在地下水影响下存在潜在失稳。与传统的边坡稳定性分析方法相比,三维数值分析优势明显。      

基于权重反分析的岩溶地面塌陷危险性评价方法研究

为能快速、准确地对覆盖型岩溶发育区进行地面塌陷危险性评价,提出了基于权重反分析的岩溶地面塌陷危险性评价方法。该方法在确定岩溶地面塌陷主要影响因素的基础上,收集整理了唐山地区100个典型工程实例,进而采用权重反分析方法,求得了岩溶地面塌陷各主要影响因素的权重,并建立了岩溶地面塌陷危险性综合评价的评分表。权重反分析结果表明,选取的5个主要因素的权重分别为：岩溶发育程度0.338、第四系底部隔水层隔水能力0.255、覆盖层厚度0.186、基岩水水位埋深0.174、距断裂距离0.047,采用新建立的评分表对100个工程实例的评价结果显示,其评价的正确率达到99%,证明该表具有良好的可行性与有效性。此外,该评分表具有评价因子易于获取、评价过程简单易懂等特点,可准确、快捷地对与唐山岩溶发育区相似区域的岩溶地面塌陷危险性给出评价,因而值得推广和应用。     

Construction and verification of a rainstorm death risk index based on grid data fusion: a case study of the Beijing rainstorm on July 21, 2012

Natural Hazards - Rainstorm disaster brings serious threat to people's life and property safety. Constructing reasonable rainstorm disaster risk index and drawing rainstorm disaster risk map...     

上海黏性土剪切带形成的数值模拟分析

各种工程事故表明：现有的土力学计算模型均未考虑应变局部化问题,故不能解释这些工程事故的发生,因此应变局部化和剪切带形成的研究成为国际土力学界研究热点之一。数值模拟是研究剪切带形成的一个重要内容。在数值模拟中首先进行剪切带形成条件的研究,接着考虑土质不均匀性的影响,引入弱单元和强单元,进行弱单元与强单元影响力的研究。     

基于LHS方法的地下水随机模拟及开采量风险性评价

地下水流数值模拟过程中,水文地质参数的不确定性对模拟结果影响很大。以内蒙古鄂尔多斯市某水源地为例,利用拉丁超立方抽样(LHS)方法获得了含水层渗透参数的随机组合,进行地下水流随机模拟。通过对观测资料与计算水位的绝对值平均(MAE)误差和误差均方根(RMSE)的统计分析,获得了模型较为稳定的随机模拟次数是243次。利用该随机模型对水源地设计开采量进行水位预测,并给出允许降深的风险性分布图。结果表明,预测水位和标准差分布符合实际情况,水位降深大于35 m的风险性最大达到75%。     

应用时间序列InSAR技术监测上海磁悬浮列车专线形变

新代高分辨军、短重访周期SAR卫星的发射运行,使得InSAR技术不仅能满足大范围地表沉降监测的数据需求,还可以监测到大型人工线状地物的形变,使得对短周期微小形变的监测和预警成为可能。本文以上海市在运营的磁悬浮列车专线为研究对象,利用时间序列分析方法对20112~F9月～2012年10月期间的15景TenaSAR-X数据进行了处理和分析,实验结果表明高分辨军SAR数据可以用于公共交通设施微小形变的监测,在公共安全领域具有广阔的应用前景。     

An evaluation of the impacts of land surface modification, storm sewer development, and rainfall variation on waterlogging risk in Shanghai

Despite continuing efforts to upgrade the urban storm sewer system since the late 1950s, the City of Shanghai is still vulnerable to persistent rainstorm waterlogging due to excess surface runoff and sewer surcharge, which frequently cause significant damage to buildings and disruption to traffic. Rapid urbanization and associated land cover changes are the major factors contributing to waterlogging. However, it is unclear to what extent changes in rainfall variability over the past few decades are also involved. This paper investigates the combined impacts of land use and land cover change, storm sewer development, and long-term variations in precipitation. Evidence of persistent waterlogging is presented first. We then give an account of land surface modifications during the process of urbanization and the development of the city??s urban storm sewer system. Statistical analysis suggests that the increase in runoff coefficient due to conversion of lands from agricultural to industrial, commercial, and residential uses is a major factor driving greater waterlogging risk. In particular, historical analysis of aerial photographs reveals the rate and extent of modification to river networks in the past few decades. The natural drainage network has shrunk by 270?km, significantly reducing the city??s capacity to transport excess surface flow. In line with other studies, we find no significant overall trends in annual rainfall totals (at Baoshan and Xujiahui). However, seasonal and monthly rainfall intensities have increased. At the daily scale, we find that compared to pre-1980s: (i) there has been an increase in the number of wet days with precipitation exceeding 25?mm (Heavy Rainfall) and decrease in those below 25?mm and (ii) the number of consecutive wet days with precipitation maximum and average exceeding the threshold known to cause waterlogging shows an increasing trend. Since rainfall intensity is expected to increase under climate change, this could further compound the impacts of land use changes and place even greater pressure on the existing storm sewer system.     

基于Monte-Carlo方法的土石围堰挡水导流风险分析

运用Monte-Carlo方法模拟施工洪水入库过程和导流建筑物泄流的随机性,通过仿真分析确定上游围堰堰前水位变化过程及其分布函数.在此基础上,根据导流建筑物的设计规模确定导流系统的风险.通过实例验证分析说明,研究方法和计算模型是可靠的、适用的.