A GIS-Based Spatial Multi-Criteria Approach for Flood Risk Assessment in the Dongting Lake Region,Hunan, Central China

Floods, the most common natural hazard in the world, cause serious loss in terms of lives, buildings, and infrastructures. As a consequence, the need for flood risk assessment has become critical. Using a semi-quantitative model and fuzzy analytic hierarchy process (FAHP) weighting approach, this paper assessed flood risk in the Dongting Lake region, Hunan Province, Central China, an area where flood hazards frequently occur. The model was designed using spatial multi-criteria analysis (SMCA) techniques in a Geographic Information System (GIS). A GIS database of indicators for the evaluation of hazard and vulnerability was created. Each indicator was analyzed, standardized, and weighted; after which, the weights of the indicators were combined to obtain the final flood risk index map. Using the flood risk index, the study area was classified into five categories of flood risk: very low, low, medium, high, and very high. The high and very high risk zones are mainly concentrated in the northern and central plains. The results obtained can provide useful information for decision makers and insurance companies.     

中国山洪灾害危险性评价

根据山洪灾害特点,对中国山洪灾害危险区进行了界定,并构建了中国山洪灾害危险性评价指标体系;采用可变模糊集方法对中国1 km×1 km分辨率山洪灾害危险性等级进行评价,分析了我国山洪灾害的空间分布特征。研究结果表明,我国约2/3国土面积可能受到山洪灾害威胁,山洪高危险性区域占国土面积的19.95%,极高危险区域占国土面积的3.92%。全国33个省级区域中,香港、福建、广西、贵州和重庆高危险区面积比例排在前5位,是山洪灾害高发区;浙江、湖北、四川等区域易受突发性小规模山洪灾害影响。研究结果客观反映了中国山洪灾害的分布特征,可为山洪灾害区划与风险分析提供科技支撑。     

Identification of Spatial Ranking of Hydrological Vulnerability Using Multi-Criteria Decision Making Techniques: Case Study of Korea

Potential flood damage (PFD), potential streamflow depletion (PSD), potential water quality deterioration (PWQD), and watershed evaluation index (WEI) have been developed to spatially quantify the hydrological vulnerability using multi-criteria decision making (MCDM) techniques. All criteria are selected on the basis of a sustainability evaluation concept (pressure-state-response model), and their weights are estimated by an Analytic Hierarchy Process, which is also a type of MCDM technique. The MCDM techniques used for the evaluation are composite programming, compromise programming, ELECTRE II, Regime method, and Evamix method; these techniques can be classified according to data availability and objectives (prefeasibility and feasibility). Furthermore, the WEI is improved to reflect the preferences of the residents with regard to management objectives through weights (of PFD, PSD, and PWQD) obtained from questionaires of residents. Finally, this study derives a procedure to identify the spatial investment prioritization using four indices.     

基于RS和GIS的县域洪涝灾害风险评估

洪涝灾害风险评价是研究洪涝灾害的重要手段之一,评价结果可为区域洪涝灾害监督预测、防洪减灾措施的制定与规划提供依据。以河北武安市为研究区域,以自然灾害风险系统理论为基础,考虑当地实际情况,从洪涝灾害的致灾危险性、灾害敏感性以及防减灾能力三个方面出发,选取降水、地形等自然因素和人口密度、经济投入水平等社会经济要素共9个评价指标,采用GIS空间分析叠加功能、加权综合评价法等方法,得出洪涝灾害风险评价结果。结果表明:武安市洪涝灾害风险分布整体呈现由中部、西南部高风险区向四周逐渐递减的特点,具体表现为河谷风险等级突出,洺河沿岸地区的风险要高于其他地区;平原风险等级明显,平原区由于易出现洪水汇入,且敏感性强的特点,易出现洪涝灾害;农耕区域的风险等级要高于林草区域。通过历史灾情数据对评价结果进行验证,本文提出的武安市洪涝灾害评估结果与实际情况一致性较高。     

洪水灾害危险性评价方法的研究与改进

洪水风险分析是防洪非工程措施的重要组成部分,而洪水危险性评价是风险分析的基础。现有的洪水危险性评价方法由于需要获得淹没水深,在对洪水风险预测时要求复杂的水力学模型和高分辨率数据的支撑,但业务化过程中常常无法满足数据要求,为了简化洪水危险性评价的过程,确保评价结果的准确性,提出了一个新的简单且综合的洪水危险性评价指标(FHI,Flood Hazard Index)。该指标以GisNet和ArcGIS为软件平台,结合分布式水文模型,依据洪灾的形成机理,综合考虑分布式流量与地形指数。结合北京山区红螺谷流域的具体情况,对新指标进行了对比检验。结果显示,FHI能够真实地反映区域洪灾随空间变化的趋势,为未来洪水危险性评价与预测的研究,提供了一个全新的思路,对洪水风险研究体系的完善具有重要的现实意义。     

Methodologies to study the surface hydraulic behaviour of urban catchments during storm events

A good knowledge of the hydraulic behaviour of an urban catchment and its surface drainage system is an essential requirement to guarantee traffic and pedestrian safety. In many cases, inlets have been situated according to spatial density criteria. Indeed a more rational location of inlets on urban catchments must be defined according to an accurate analysis of the relationship between street flow and inlet hydraulic efficiency. Moreover we lack specific hazard criteria in terms of the maximum acceptable flow depths and velocities on the streets that do not cause problems to pedestrians. In this paper the results of two different experimental campaigns are presented. The first was carried out to evaluate inlet hydraulic efficiency; the second was carried out to address the pedestrian stability in urban flood conditions, whose aim was to propose new hazard criteria. On the basis of the experimental results, a methodology was developed to assess flood hazard in urban areas during storm events. If a refined topographic representation of urban areas is available, a two-dimensional numerical simulation of urban flooding can be performed using complete shallow water equations. According to this approach a numerical application for flood hazard assessment in a street of Barcelona is shown.     

Flood Vulnerability Analysis by Fuzzy Spatial Multi Criteria Decision Making

Prioritization the sub-basins available in a basin to flood vulnerability analysis can be discussed in the form of a spatial multi criteria decision making (SMCDM) problem. In this research a fuzzy planning support system based on the spatial analysis using tow multi criteria decision making methods, Analytic Hierarchy Process (AHP) and TOPSIS (Technique for order-preference by similarity to ideal solution) is used. AHP method is used to determine the structure of decision making process and to estimate criteria weights and TOPSIS model is used to rank the sub-basins of Tehran urban basin as a study area regarding the flood vulnerable areas. Also in order to perform spatial analysis for decision-making process, a developed toolbox is used within the Geographic Information System (GIS). In this research a model is presented in which some vague concepts such as weight of decision making criteria are expressed in the form of linguistic variables to be converted to triangular fuzzy numbers. Finally, the sensitivity of model was analyzed by changing the weights of decision making criteria and providing of ranking scenarios. The results show the optimum alternatives for mitigation flood vulnerability in the study area.

     

Groundwater Overexploitation Causing Land Subsidence: Hazard Risk Assessment Using Field Observation and Spatial Modelling

Hazard risk assessment of land subsidence is a complicated issue aiming at identifying areas with potentially high environmental hazard due to land subsidence. The methods of hazard risk assessment of land subsidence were reviewed and a new systematic approach was proposed in this study. Quantitative identification of land subsidence is important to the hazard risk assessment. Field observations using extensometers were used to determine assessment indexes and estimate weights of each index. Spatial modelling was also established in ArcGIS to better visualize the assessment data. These approaches then were applied to the Chengnan region, China as a case study. Three factors, thickness of the second confined aquifer, thickness of the soft clay and the annual recovery rate of groundwater level were incorporated into the hazard risk assessment index system. The weights of each index are 0.33, 0.17 and 0.5 respectively. The zonation map shows that the high, medium and low risk ranked areas for land subsidence account for 9.5?%, 44.7?% and 45.8?% of the total area respectively. The annual recovery rate of groundwater level is the major factor raising land subsidence hazard risk in approximately half of the study area.     

基于模糊层次分析法的京津冀洪灾风险评价

针对京津冀一体化发展的总体需求,采用模糊层次分析法,开展京津冀地区洪灾风险评价研究。首先从致灾因子、孕灾环境和承灾体三个方面分析遴选评价指标,采用模糊算法与层次分析法相结合,构造模糊一致判断矩阵确定各指标相对权重,并利用GIS技术将多维指标映射为一维评判准则,建立京津冀地区洪灾风险综合评价模型,确定洪灾风险空间分布状况,实现京津冀洪灾风险等级区划。结果表明:中高风险区主要分布于滦河、大清河及子牙河沿岸,特别是子牙河南支滏阳河上游、大清河南支河系上游以及白洋淀周边区域风险较高;北京、天津、石家庄等中心城区局部区域风险较低,城乡防洪标准提高后,相应区域的洪灾风险等级进一步降低。洪灾风险计算方法和区划结果具有合理性,研究成果可为区域洪灾风险区划和京津冀协同发展规划提供参考。     

Spatio-Temporal Multi-Criteria Optimization of Reservoir Water Quality Monitoring Network Using Value of Information and Transinformation Entropy

Identifying optimal Water Quality Monitoring Stations (WQMS) with high values of information on the entire reservoir status, instead of all potential WQMS would significantly reduce the monitoring network expenditure while providing adequate spatial coverage. This study presented a new methodology for spatio-temporal multi-criteria optimization of reservoir WQMS based on Value of Information (VOI), Transinformation Entropy (TE), Non-dominated Sorting Genetic Algorithm II (NSGA-II), Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE), and IRanian Water Quality Index (IRWQI). Although, all mentioned methods and concepts are well-known and have been used in water resources management, but their integration into a specific application for spatio-temporal multi-criteria optimization of reservoir WQMS is definitely an innovation and a contribution to improvement of WQMS design. More specifically, maximizing VOI as a decision-makers’ design criteria for optimization of WQMS, and considering spatial and temporal variations of water quality at different reservoir depths are new innovations in this research. The multi-objective optimization model was based on three objectives: 1) minimizing costs; 2) maximizing VOI; and 3) minimizing TE (redundant information). Considering these objectives, the NSGA-II multi-objective optimization method was used to find Pareto-optimal solutions. The most preferable solution was then determined using PROMETHEE multi-criteria decision making method. The proposed methodology was applied to Karkheh Reservoir with more than 5 billion cubic meter capacity and 60 km length that is one of the largest reservoirs in Southwestern Iran, however, the proposed approach has the ability to be generalized for any generic reservoir. Considering equal weights for criteria, PROMETHEE method resulted in 6 optimized WQMS out of 60 potential ones and a period of 25 days for optimal sampling interval. The optimized monitoring stations were mainly located at deep parts where most water quality variations are expected to occur. To show sensitivity of the model to different weights, 4 scenarios with various relative weights were evaluated in the PROMETHEE method. Results indicated that by increasing the weight of the second criterion (maximizing VOI), the number of optimized WQMS increased and the sampling interval decreased.     

区域洪灾风险评价方法初探 -以浙江省为例

本文选取我国浙江省作为研究区,以其县域作为基础的计算单元,从洪水灾害系统理论出发,构建洪灾风险评估模型和风险因子指标体系对宏观区域上的洪灾风险评价方法进行了探讨。根据洪水灾害风险的原理,结合致灾因子危险性、承灾体暴露性和易损性、区域防灾力等要素选取了巧个风险评价指标,并为各风险因子及其基础指标分配了权重。根据所建立的计算模型和风险分级方法,对研究区的洪灾风险等级及风险类型做了定量化分析。经计算,浙江省高等级的洪灾风险集中分布于浙北的冲积平原区和浙东的沿海丘陵平原区,在浙西的金华衡州盆地也有高等级洪灾风险呈点状分布。评价结果可用于指导浙江省的洪水风险管理和防灾减灾措施建设。     

基于简化内涝模型的上海城区内涝危险性评价

根据城市的特征,基于SCS模型和GIS空间分析功能构建了一个简化的城市内涝模型(SUWM)。该模型主要由城市地形模型、城市降雨径流模型以及GIS空间分析模型构成。选取上海市中心城区对暴雨内涝进行模拟并进行危险性评价。结果显示:①不同概率的降水引发的内涝危险性不同。总体上,降雨量越大,形成的内涝积水越深,危险性也就越大;②相同概率的降水引发的内涝危险性在不同区域也不相同。总体上,杨浦、长宁和虹口区内涝危险性最高;徐汇、普陀和闸北区内涝危险性处于中等水平;静安区、黄浦区和卢湾区内涝危险性最低。     

空间信息技术与防洪减灾现代化

我国洪水灾害频繁,洪灾损失严重,防洪减灾将是一项长期而艰巨的任务。在防洪减灾研究中,必须积极引进当今社会最新科研成果,以高新技术改造水利传统产业,以水利信息化带动水利现代化。以遥感、地理信息系统和全球定位系统为支撑的空间信息技术可以广泛地应用于防洪减灾中,是防洪减灾现代化的重要基础。本文分析了空间信息技术在防洪减灾中的作用,并对空间信息技术在防洪减灾中的应用趋势作出展望。     

Groundwater Recharge Zone Mapping Using GIS-Based Multi-criteria Analysis: A Case Study in Central Tunisia (Maknassy Basin)

The groundwater recharge zone mapping often requires a large amount of spatial information and criteria. Geographic information systems are capable of managing large amount of spatially related information, providing the ability to integrate multiple layers of information for multi-criteria analysis. To show the capabilities of GIS techniques for mapping groundwater refill zone in arid area, a study was carried out in the Maknassy basin located in Central Tunisia. This evaluation incorporates historic rainfall data analysis, watershed drainage density, surficial geology and aquifer boundary conditions. The study basin is categorized according to the previous criteria. Multi-criteria analysis is performed to evaluate suitability to the groundwater recharge for each factor, according to its associated weight. The thematic layers were integrated with one another using the weighted aggregation method to derive the groundwater recharge map. The results demonstrated that the GIS methodology has good functionality for mapping groundwater recharge zone.     

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.

     

Robustness,Uncertainty and Sensitivity Analyses of the TOPSIS Method for Quantitative Climate Change Vulnerability: a Case Study of Flood Damage

Multi-criteria decision making (MCDM) techniques have been used to evaluate and rank the spatial flood vulnerability to climate change. However, various sources of uncertainty, such as the determination of evaluation criteria, the assignment of criteria weights and performance values, exist in the application of MCDM methods. In this study, three existing methods were combined to quantify the risk and uncertainties inherent to the process of climate change vulnerability assessment, which is called the TOPSIS-based Robustness-Uncertainty-Sensitivity (RUS) approach. The A1B scenario was used to assess the vulnerability of seven metropolitan cities in South Korea to climate change. Twenty indicators that are closely related to the cause of and deterioration from the flood risk and the resulting damages were selected by two surveys of experts, and the weights of these factors were determined by using the Delphi technique, which can derive the subjective weights. Based on the derived weights, the vulnerability ranking was calculated using the TOPSIS method, one of the most popular MCDM methods. This TOPSIS-based RUS approach was used to analyze the robustness of the vulnerability rankings for the assessed cities, to derive the minimum changed weights of the single and multiple criteria that determine the rank equivalence (or reversal) between any two cities and to check the sensitivities of the performance values to the vulnerability rankings. This study showed the effectiveness of the RUS approach for assessing the vulnerability to climate change, demonstrating the application of flood vulnerability.     

组合赋权2模糊聚类算法的改进及其 在洪灾风险评价的应用

针对洪水灾害风险评价中单一赋权法存在一定局限性和风险等级难以客观划分的问题, 提出改进组合赋权-模糊聚类算法, 开展洪水灾害风险评价研究。考虑洪灾危险性、敏感性和易损性等 3 个方面筛选构建评价指标体系, 并分别采用直觉模糊层次分析法和 VC-CRITIC 法赋予主、客观权重, 通过改进博弈论组合赋权法计算最优组合权重, 加权计算不同评价单元洪灾风险度, 利用高斯混合模型模糊聚类算法划分区域洪水灾害风险等级。以茨南淝左片防洪保护区遭遇淮河干流百年一遇洪水为例进行洪灾风险评价算法应用研究, 结果表明: 极高风险区和 高风险区共占保护区总面积的 24. 87 % , 基本为淹没水深较大、地形位指数较低和社会经济价值较高的区域。评价结果较为合理可靠, 所提改进组合赋权2模糊聚类算法可为防洪保护区洪水灾害风险评价和防灾减灾决策提供技术支持。     

基于MIKE Flood的中小河流溃堤洪水演进数值模拟

针对水文资料缺乏的中小河流,以贵溪市罗塘河下游段为例,应用MIKE软件对河流溃堤洪水演进进行了研究。采用瞬时单位线法推求断面各频率的设计洪水,并将其作为洪水演进模型的输入;利用MIKE软件建立了贵溪市罗塘河下游段的一、二维耦合水动力模型,对该河下游段溃堤洪水演进过程进行了模拟;通过模拟分析,得到了溃口流量过程和堤防保护区洪水淹没过程。研究成果可为中小河流洪水风险分析和灾害损失评估提供技术支撑。     

降雨移动对河道洪峰影响研究——以深圳为例

全球气候变化和快速城镇化加剧了城市降雨过程的不稳定性,进而影响城市河道洪水过程,加剧了城市洪涝防治难度。本文以深圳市河湾片区为研究区,利用数值模拟方法研究了降雨移动方向对城市河道洪峰的影响。基于雨强和移动方向的不同组合构建了 1300 个降雨方案,并利用城市洪涝模型分别模拟了各降雨方案条件下的河道洪水过程,从模拟结果中提取河道断面的洪峰流量以构建评价指标,在全区、河道、断面等不同尺度进行了统计和对比分析。结果表明：随着雨强增加,降雨移动方向对河道洪峰的影响会减小;河道下游断面受影响程度明显高于上游断面;单个断面的洪峰受影响程度与降雨过程的移动方向呈现出较强相关性。研究结果可为城市洪涝防治和洪水风险评估提供参考。     

Flood risk mapping at European scale.

The aim of this article is to illustrate a framework for flood risk mapping at pan-European scale produced by the Weather-Driven Natural Hazards (WDNH) action of the EC-JRC-IES. Early results are presented in the form of flood risk index maps. We assess several flood risk factors that contribute to the occurrence of flood disasters. Among the causal factors of a flood disaster one is triggering a natural event in the form of extreme precipitation and consequently extreme river discharge and extreme flood water levels. The threatening natural event represents the hazard component in our assessment. Furthermore exposure and vulnerability are anthropogenic factors that contribute also to flood risk. In the proposed approach, flood risk is considered on the light of exposure, vulnerability and hazard. We use a methodology with a marked territorial approach for the assessment of the flood risk. Hence, based on mathematical calculations, risk is the product of hazard, exposure and vulnerability. Improvements on datasets availability and spatial scale are foreseen in the next phases of this study. This study is also a contribution to the discussion about the need for communication tools between the natural hazard scientific community and the political and decision making players in this field.