Slope vulnerability to earthquakes at subregional scale, using probabilistic techniques and geographic information systems

The susceptibility of slopes to failure during earthquakes is calculated, in terms of critical horizontal acceleration, on a subregional scale for the upper part of the Serchio River basin (Tuscany, Italy). According to the working scale (1:10 000) and to the availability and accuracy of the input data, the infinite slope analysis was judged to be the most appropriate method, but particular attention was devoted to the error evaluation due to spatial variability of the geotechnic, geometric, and hydrologic parameters. A geologic, geomorphologic and hydrologic survey of the area was therefore performed, and the geotechnic parameters were collected at local administrations. All the data were stored in a GIS, used as a tool to build the spatial and attribute data base and to prepare the input data layers for the stability analysis. In order to assess the variability of geotechnic parameters, a statistical analysis was performed to assign the best-fitting probability distribution to cohesion, angle of internal friction and unit weight of the soil. As hydrogeologic data were not available for the area, only surface hydrology information could be used; a map of probability of spring occurrences was derived by a bayesian method, the Weight of Evidence Modelling, and was used as groundwater indicator. A Monte Carlo procedure and a first-order second-moment method were applied and compared as error estimators in assessing the slope susceptibility to failure. The differences between the two methods are discussed, and two maps showing, respectively, the critical horizontal acceleration and the probability of failure associated with each slope are presented, together with the curve plotting the reliability index against the probability of failure.     

Seismic vulnerability assessment for Montreal

In Canada, Montreal is the second city with the highest seismic risk. This is due to its relatively high seismic hazard, old infrastructures and high population density. The region is characterised by moderate seismic activity with no recent record of a major earthquake. The lack of historical strong ground motion records for the region contributes to large uncertainties in the estimation of hazards. Among the sources of uncertainty, the attenuation function is the main contributor and its effect on estimates of risks is investigated. Epistemic uncertainty was considered by obtaining damage estimates for three attenuation functions that were developed for Eastern North America. The results indicate that loss estimates are highly sensitive to the choice of the attenuation function and suggest that epistemic uncertainty should be considered both for the definition of the hazard function and in loss estimation methodologies. Seismic loss estimates are performed for a 2% in 50 years seismic threat, which corresponds to the design level earthquake in the national building code of Canada, using HAZUS-MH4 for the Montreal region over 522 census tracts. The study estimated that for the average scenario roughly 5% of the building stock would be damaged with direct economic losses evaluated at 1.4 billion dollars for such a scenario. The maximum number of casualties would result in approximately 500 people being injured or dead at a calculated time of occurrence of 2?pm.     

Validation and development of composite indices for measuring vulnerability to earthquakes using a socio-economic perspective

While many approaches for assessing earthquake risk exist within the literature and practice, it is the dynamic interrelationships between earthquake hazard, physical risk, and the social conditions of populations that are the focal point for disaster risk reduction. Here, the measurement of vulnerability to earthquakes (i.e., characteristics that create the potential for harm or loss) has become a major focus area. However, metrics aimed at measuring vulnerability to earthquakes suffer from several key limitations. For instance, hazard and community context are often ignored, and attempts to validate metrics are largely non-existent. The purpose of this paper is to produce composite indices of the vulnerability of countries to earthquakes within three topical areas: social vulnerability, economic vulnerability, and recovery potential. To improve upon the status quo in indicators development for measuring vulnerability to seismic events, our starting point was to: (1) define a set of indicators that are context specific to earthquakes as defined by the literature; (2) delineate indicators within categorical areas of vulnerability that are easy to understand and could be put into practical use by DRR practitioners; and (3) propose indicators that are validated using historical earthquake impacts. When mapped, the geographic variations in the differential susceptibility of populations and economies to the adverse effects of damaging earthquake impacts become evident, as does differential ability of countries to recover from them. Drivers of this geographic variation include average country debt, the type and density of infrastructure, poverty, governance, and educational attainment, to name just a few.

     

Analysis of flood vulnerability and assessment of the impacts in coastal zones of Bangladesh due to potential sea-level rise

The 4th IPCC report highlights the increased vulnerability of the coastal areas from floods due to sea-level rise (SLR). The existing coastal flood control structures in Bangladesh are not adequate to adapt these changes and new measures are urgently necessary. It is important to determine the impacts of SLR on flooding to analyse the performance of the existing structures and corresponding impact to plan for suitable adaptation and mitigation measures to reduce the impacts of floods on coastal zone. The study aims to develop a comprehensive understanding of the possible effects of SLR on floods in the coastal zone of Bangladesh. A hydrodynamic model, which is a combination of surface and river parts, was utilized for flood simulation. The tool was applied under a range of future scenarios, and results indicate both spatial variability of risk and changes in flood characteristics between now and under SLR. Estimated impact on population, infrastructure and transportation is also exposed. These types of impact estimation would be of value to flood plain management authorities to minimize the socio-economic impact.     

Scales as a challenge for vulnerability assessment

The aim of this paper is to introduce scale as a basic tool for improving the conceptual structure of vulnerability assessments. The terminology useful for vulnerability assessments and the current use of scale issues in theoretical vulnerability frameworks will be discussed briefly. Two case studies working on sub-national and on local level will demonstrate problems as well as benefits resulting from scale implications. Both assessments analyse vulnerability in context to river floods in Germany. In order to develop a spatial comparison and to integrate topics like environment and society, vulnerability assessments need to be aware of scale implications. The main point is that a scale debate on a broader spectrum than just in technical spatial terms is missing in vulnerability and risk conceptualisations so far. Vulnerability assessments and scale are highly intertwined, not only in technical application but also in conceptualisation, which needs more scientific development.     

Regional assessment and mapping of groundwater vulnerability to contamination

In many regions the use of groundwater for water supply is limited by the increase in contamination of aquifers. The problem of contamination requires the development of new approaches in assessing areas in which groundwater is vulnerable to contamination. A brief analysis of the present day level of methods for regional evaluation and mapping of areas in which groundwater is vulnerable is presented.     

潮滩脆弱性评估方法研究综述

由于潮滩组成要素不稳定、地理区位特殊以及人为因素的制约,导致潮滩极易受外在和内在因素的影响,发生自然系统脆弱性(包括固有脆弱性和特殊脆弱性)。在总结国内外关于潮滩脆弱性评估方法(诸如综合指数法、层次分析法等综合评估方法以及主成分分析法、高程面积法等单一影响评价法)基础上,根据潮滩脆弱性评估的选择原则,构建了潮滩脆弱性评估指标体系,以期为沿海地区的可持续发展提供理论和技术支撑。     

Analysis of the global tsunami data for vulnerability and risk assessment

For the assessment of tsunami risk and vulnerability, one has to make use of past tsunami observations. The most comprehensive tsunami databases for the world have been prepared by the National Geophysical Data Center of USA which are listed on their website for all the four oceans as well as the following marginal seas: Caribbean Sea, Mediterranean Sea, Black Sea, Red Sea and Gulf of Mexico. The dataset goes back as far as the first century AD and lists the events on a confidence rating scale of 0–4; 0 being an erroneous entry and 4 being a definite tsunami. Based on these various datasets for different geographical areas, a comprehensive global dataset was prepared in this study, which included only tsunami events with confidence rating of 3 and 4, meaning either probable or definite. In this composite and abridged global tsunami database there is no distinction either according to geography or tsunami strength as implied by its impact on the coast. A simple and straightforward statistical analysis suggests an almost complete randomness and no patterns that can be used for future tsunami predictions with a few minor exceptions.     

中国大陆斑岩铜矿资源潜力定量评价

应用美国"三部式"资源评价方法原理,对中国大陆斑岩铜矿成矿地质背景、时空分布规律、矿床模型等方面研究,圈出46个远景区;以中国1999年金属储量数据库和区划矿产地数据为基础,建立了铜矿数据库共984个,分不同类型进行品位吨位的研究,以此为基础构造出数字找矿模型和开发出矿产资源定量评价模型程序,并计算了每个远景区的概率资源量,为评估中国斑岩铜矿资源潜力提供了参照。     

Physical vulnerability assessment of buildings exposed to landslides in India

Natural Hazards - Safe structures are the backbone of human coping capacity towards healthy living that can contribute significantly in reducing risk during hazards. However, due to various natural...     

改进的DRASTIC模型在地下水易污染性模糊评价中的应用

为了有效避免地下水系统遭受污染,保护地下水资源,采用改进的DRASTIC模型对地下水易污染性进行了评价.鉴于DRASTIC模型的诸多缺陷,将模糊综合评价方法运用到模型中,构建了各评价指标于各个级别的最优相对隶属度矩阵;引用语气算子确定指标权重,计算出了研究区样本集的级别特征值向量.将样本的易污染性进行排序,用研究区样段的水质评价结果进行了验证,结果证明,易污染性程度越高的地区综合评价水质越差;为进一步验证评价方法的真实性,将易污染性排序结果与传统DRASTIC法评价排序结果进行对比,两种方法排序一致.可见,本次改进的模型在克服了DRASTIC的诸多缺陷的同时,使得计算结果真实、可靠,且更加体现了计算过程的科学性与合理性.     

区域泥石流易损性评价

以联合国公布的易损性定义为基础,论述了影响区域易损性的代表性因子及其量化方法,探讨了各因子与易损性的相互关系,论证了区域泥石流易损性评价的建模过程及其数学表达.区域泥石流易损性反映泥石流作用下垫面的社会、经济和环境属性,与固定资产投资、国内生产总值和土地资源价值以及人口密度和人口质量(年龄大小、教育水平、富裕程度)有关.区域泥石流易损性定量表达为财产指标赋值和人口指标赋值平均值的平方根.以四川凉山州为研究实例,对此评价方法进行了应用.     

Aquifer vulnerability and potential risk assessment: application to an intensely cultivated and densely populated area in Southern Italy

The use of indices, describing aquifer vulnerability and the risk of groundwater pollution, is a basic tool for the implementation of a sound water management plan, especially in densely populated and intensely cultivated areas. In this study, the groundwater contamination risk of the Caserta Plain (Southern Italy) was assessed through the integration of hazards defined on the basis of the different land uses, of the intrinsic vulnerability calculated by applying the SINTACS model and of the groundwater value evaluated by considering water wells density. In order to evaluate the evolution of the risk of groundwater pollution, the proposed methods were applied in the study area for both 2001 and 2009. The resulting specific vulnerability (SINTACS-L) and the risk (GRA) maps, created in a GIS environment, were validated by the comparison with the nitrate concentration distribution. The application of the proposed approach to the study area highlighted the strengths and weaknesses of each method and, at the same time, showed that their combination can provide an overall view of the threats posed to groundwater resources by the human activities affecting the territory. Considering both the benefits and the issues of the proposed approach, overall, the groundwater risk map is thought to be a robust tool to support water managers in defining future plans for water resources exploitation and land use.