Vulnerability to environmental hazards in the Ciudad Juárez (Mexico)–El Paso (USA) metropolis: A model for spatial risk assessment in transnational context

The purpose of this paper is to present a geographic information system (GIS)-based method for mapping risk to environmental hazards. Framed by the hazards literature, the method has been developed to specifically overcome issues of data compatibility associated with transnational contexts. The approach is elaborated in reference to a project in which risk was spatially characterized, using a suite of biophysical and social indicators, for the Ciudad Juárez (Mexico)–El Paso (USA) metropolis. Results reveal clear spatial disparities in hazard vulnerability, both within and between the two cities, based on the differential allocation of selected risk factors. The case indicates that future international analyses will be advanced by the clear definition of concepts, the systematic mining of compatible variables, and the selection of valid risk indicators based on criteria that balance the need to incorporate contextual specificity with general comparability.     

遥感技术在洪涝灾害防治体系建设中的应用

本文综述了遥感技术在洪涝灾害防治体系建设中的应用 ,包括洪涝灾害背景数据的建设和更新、洪涝灾害承灾体的识别和信息提取、洪涝灾害相关模型计算以及灾害监测、减灾救灾应急系统等方面 ,并对目前应用中存在的主要问题和发展方向进行了探讨.     

Groundwater vulnerability and risk mapping for the Basaltic aquifer of the Azraq basin of Jordan using GIS, Remote sensing and DRASTIC

Water consumption in Jordan already exceeds renewable freshwater resources by more than 20% and, after the year 2005, freshwater resources are likely to be fully utilised. Over 50% of supply derives from groundwater and this paper focuses on a small part of the northern Badia region of Jordan that is underlain by the Azraq groundwater basin where it has been estimated that annual abstraction stands at over 100% of the projected safe yield. While water supply is a crucial issue, there is also evidence to suggest that the quality of groundwater supplies is also under threat as a result of salinisation and an increase in the use of agrochemicals. Focusing on this area, this paper attempts to produce groundwater vulnerability and risk maps. These maps are designed to show areas of greatest potential for groundwater contamination on the basis of hydro-geological conditions and human impacts. All of the major geological and hydro-geological factors that affect and control groundwater movement into, through, and out of the study area were incorporated into the DRASTIC model. Parameters included; depth to groundwater, recharge, aquifer media, soil media, topography, and impact of the vadose zone. The hydraulic conductivity of the aquifer was not included in calculating the final DRASTIC index for potential contamination due to a lack of sufficient quantitative data. A Geographical Information System (GIS) was used to create a groundwater vulnerability map by overlaying the available hydro-geological data. The resulting vulnerability map was then integrated with a land use map as an additional parameter in the DRASTIC model to assess the potential risk of groundwater to pollution in the study area. The final DRASTIC model was tested using hydrochemical data from the aquifer. Around 84% of the study area was classified as being at moderate risk while the re mainder was classified as low risk. While the analysis of groundwater chemistry was not conclusive, it was encouraging to find that no well with high nitrate levels was found in the areas classified as being of low risk suggesting that the DRASTIC model for this area provided a conservative estimate of low risk areas. It is recognised that the approach adopted to produce the DRASTIC index was limited by the availability of data. However, in areas with limited secondary data, this index provides important objective information that could be used to inform local decision making.     

Quantitative landslide risk assessment and mapping on the basis of recent occurrences

A quantitative procedure for mapping landslide risk is developed from considerations of hazard, vulnerability and valuation of exposed elements. The approach based on former work by the authors, is applied in the Bajo Deba area (northern Spain) where a detailed study of landslide occurrence and damage in the recent past (last 50 years) was carried out. Analyses and mapping are implemented in a Geographic Information System (GIS).The method is based on a susceptibility model developed previously from statistical relationships between past landslides and terrain parameters related to instability. Extrapolations based on past landslide behaviour were used to calculate failure frequency for the next 50 years. A detailed inventory of direct damage due to landslides during the study period was carried out and the main elements at risk in the area identified and mapped. Past direct (monetary) losses per type of element were estimated and expressed as an average ‘specific loss’ for events of a given magnitude (corresponding to a specified scenario). Vulnerability was assessed by comparing losses with the actual value of the elements affected and expressed as a fraction of that value (0–1).From hazard, vulnerability and monetary value, risk was computed for each element considered. Direct risk maps (€/pixel/year) were obtained and indirect losses from the disruption of economic activities due to landslides assessed. The final result is a risk map and table combining all losses per pixel for a 50-year period. Total monetary value at risk for the Bajo Deba area in the next 50 years is about 2.4 × 10⁶ Euros.     

A method for assessing regional debris flow risk: an application in Zhaotong of Yunnan province (SW China)

Based on the definitions of the United Nations, the assessment of risk involves the evaluation of both hazard and vulnerability. This forms the basis of a generalized assessment model of debris flow risk. Hazard is a measure of the threatening degree of an extreme event and is expressed theoretically as a function of event magnitude and frequency of occurrence. Mathematically, it is the definite integral area under the magnitude–frequency curve. Based on the need for a model applicable in regions that lack data, a new method that incorporates theoretical concepts with empirical analysis is presented to calculate the regional hazardousness of debris flows. Debris flow hazard can be estimated from gully density, mean annual rainfall and percentage of cultivated land on steep slope. Vulnerability is defined as the potential total maximum losses due to a potential damaging phenomenon for a specified area and during a reference period. On a regional scale, it is dependent on the fixed assets, gross domestic product, land resources and population density, as well as age, education and wealth of the inhabitants. A nonlinear, power-function model to compute the vulnerability degree is presented. An application of the proposed method to Zhaotong prefecture of Yunnan province, SW China, provides high accuracy and reasonable risk estimates. The highest risk of debris flow is in Zhaotong county with a value of 0.48; the lowest risk of debris flow is in Yanjin county with a value of 0.16. The other counties have debris flow risks ranging from 0.22 to 0.46. This provides an approach for assessing the regional debris flow risk and a basis for the formulation of a regional risk management policy in Zhaotong prefecture.     

遥感技术在湖泊环境变化研究中的应用和展望

遥感技术由于能够快速、宏观的获得研究区域的数据,已成为湖泊环境动态变化监测的重要技术手段。高分辨率的卫星遥感图像不仅可以为准确判读湖区地质地貌、自然与人为作用下的环境变化、盐湖矿产资源的分布等提供直观的影像,还能为湖泊水质监测、水深检测、水面温度反演以及盐湖卤水动态分析提供有价值的信息。遥感技术在湖泊环境变化研究中的应用正逐步从定性发展为定量研究,因此,对于区分湖泊水体中不同组分对遥感图像各光谱值的贡献等遥感机理的认识及理论尚需进一步深化,同时需要对处理遥感数据所运用的统计分析方法做进一步的改进以建立更加完善的遥感模型。今后,遥感技术和地理信息系统等多种信息处理工具的结合将是环境信息系统发展的主要方向。     

西藏盐湖TM影像遥感分析

利用TM影像及数据,对西藏盐湖做了全面的分析探讨,总结了盐湖的遥感影像特征,建立了遥感解译标志,并利用不同盐度水体的反射率和主成分分析对盐湖做了遥感信息的探索性研究。以此为依据,对西藏全区盐湖进行了判读,识别出大于1km2的盐湖区392个,为以后从事西藏盐湖研究奠定了良好的基础。     

Probabilistic landslide risk analysis considering direct costs in the area north of Lisbon (Portugal)

The purpose of the present study is the analysis of landslide risk for roads and buildings in a small test site (20 km²) in the area north of Lisbon (Portugal). For this purpose, an evaluation is performed integrating into a GIS information obtained from multiple sources: (i) landslide hazard; (ii) elements at risk; and (iii) vulnerability. Landslide hazard is assessed on a probabilistic basis for three different types of slope movement (shallow translational slides, translational slides and rotational slides), based on some assumptions such as: (i) the likelihood of future landslide occurrence can be measured through statistical relationships between past landslide distribution and specified spatial data sets considered as landslide predisposing factors; and (ii) the rainfall combination (amount–duration) responsible for past slope instability within the test site will produce the same effects (i.e. same type of landslides and similar total affected area), each time they occur in the future. When the return period of rainfall triggering events is known, different scenarios can be modelled, each one ascribed to a specific return period. Therefore, landslide hazard is quantitatively assessed on a raster basis, and is expressed as the probability for each pixel (25 m²) to be affected by a future landslide, considering a rainfall triggering scenario with a specific return period. Elements at risk within the test site include 2561 buildings and roads amounting to 169 km. Values attributed to elements at risk were defined considering reconstruction costs, following the guidelines of the Portuguese Insurance Institute. Vulnerability is considered as the degree of loss to a given element resulting from the occurrence of a landslide of a given magnitude. Vulnerability depends not only on structural properties of exposed elements, but also on the type of process, and its magnitude; i.e., vulnerability cannot be defined in absolute terms, but only with respect to a specific process (e.g. vulnerability to shallow translational slides). Therefore, vulnerability was classified for the three landslide groups considered on hazard assessment, taking into account: (i) landslide magnitude (mean depth, volume, velocity); (ii) damage levels produced by past landslide events in the study area; and (iii) literature. Finally, a landslide risk analysis considering direct costs was made in an automatic way crossing the following three layers: (i) Probabilistic hazard map for a landslide type Z, considering a particular rainfall triggering scenario whose return period is known; (ii) Vulnerability map (values from 0 to 1) of the exposed elements to landslide type Z; and (iii) Value map of the exposed elements, considering reconstruction costs.     

Ten major rivers in monsoon Asia-Pacific: An assessment of vulnerability

An assessment of socioeconomic-environmental vulnerability of the ten major river basins in the Monsoon Asia-Pacific region was performed. The rivers include Indus, Ganges-Brahmaputra-Meghna (GBM), Irrawaddy, Salween, Chao Phraya, Mekong, Red River, Pearl River, Yangtze and Yellow River. The study looked at a combination of various issues, usually investigated in isolation from each other, on a sub-continental scale by using the river basins as the geographical entities for the study. The analysis was conducted by using various geospatial databases including data on nature and environment, demography, governance, water scarcity as well as social and economic development. A vulnerability profile for each of the river basins was produced by using two different approaches. We found that the South Asian basins (Indus and GBM) appeared essentially more vulnerable than the other investigated basins. The other basins are roughly at the same vulnerability level, but their vulnerability profiles differ substantially. The Chinese basins and the Red River are particularly vulnerable to environmental factors. The weak points of Irrawaddy and Salween are in the hazards and economic development, whereas the former is a challenge to Mekong as well. Only Indus and Yellow River suffer from considerable water scarcity. The other basins except GBM are relatively well-off with the social matters. A transparent and pragmatic river basin vulnerability assessment approach was developed, which can be used in any large river basin of the world, producing intercomparable results. The approach allows further decoupling of the used indices in the case of more specific and targeted analyses without losing the comparability of the overall results.     

Remote sensing and geomorphometry for studying relief production in high mountains

Mountain topography is the result of highly scale-dependent interactions involving climatic, tectonic, and surface processes. No complete understanding of the geodynamics of mountain building and topographic evolution yet exists, although numerous conceptual and physical models indicate that surficial erosion plays a significant role. Mapping and assessing landforms and erosion in mountain environments is essential in order to understand landscape denudation and complex feedback mechanisms. This requires the development and evaluation of new approaches in remote sensing and geomorphometry. The research herein evaluates the problem of topographic normalization of satellite imagery and demonstrates the use of terrain analysis using a digital elevation model (DEM) to evaluate the relief structure of the landscape in the western Himalaya. We specifically evaluated the Cosine-correction and Minnaert-correction methods to reduce spectral variation in imagery caused by the topography. Semivariogram analyses of the topography were used to examine the relationships between relief and surface processes. Remote-sensing results indicate that the Minnaert-correction method can be used to reduce the “topographic effect” in satellite imagery for mapping, although extreme radiance values are the result of not accounting for the diffuse-skylight and adjacent-terrain irradiance. Geomorphometry results indicate that river incision and glaciation can generate extreme relief, although the greatest mesoscale relief is produced by glaciation at high altitudes. At intermediate altitudes, warm-based glaciation was found to decrease relief. Our results indicate that glaciation can have a differential influence on the relief structure of the landscape. Collectively, our results indicate that scale-dependent analysis of the topography is required to address radiation transfer issues and the polygenetic nature of landscape denudation and relief production.     

区域地质灾害风险评估模型的初建--以广州市崩塌灾害为例

地质灾害的研究必须基于其自然和社会经济的双重属性特征,并把它作为一项系统工程来研究;风险评估是这系统工程中不可或缺的重中之重内容,也是新世纪地质灾害防灾减灾领域的前沿和热点.鉴于地质灾害风险评估研究现状,初步探讨了区域地质灾害风险评估模型的构建,即基于格网单元的地质灾害危险性评价、基于行政单元的社会经济易损性评价和基于危险度和易损度乘积的区域风险评估.同时以广州市崩塌灾害为例,采用该模型进行评估并取得了良好的效果.     

Mapping the vulnerability of crop production to drought in Ghana using rainfall, yield and socioeconomic data

This study evaluates new multi-scale, multi-indicator methods for assessing the vulnerability of crop production to drought at a national and regional scale. It does this by identifying differences across and within ten regions of Ghana, a country that faces many climate and crop production challenges typical of sub-Saharan Africa. In particular, we illustrate how a quantitative national and regional study is a critical first step in assessing differences in the drought sensitivity of food production systems and show how such an assessment enables the formulation of more targeted district and community level research that can explore the drivers of vulnerability and change on a local-scale. Finally, we propose methodological steps that can improve drought sensitivity and vulnerability assessments in dynamic dryland farming systems where there are multiple drivers of change and thresholds of risk that vary in both space and time. Results show that the vulnerability of crop production to drought in Ghana has discernible geographical and socioeconomic patterns, with the Northern, Upper West and Upper East regions being most vulnerable. Partly, this is because these regions have the lowest adaptive capacity due to low socioeconomic development and have economies based on rain-fed agriculture. Within these regions we find considerable differences between districts that can be explained only partly by socioeconomic variables with further community and household-scale research required to explain the causes of differences in vulnerability status. Our results highlight that national and regional scale multi-indicator vulnerability assessments are a vital (and often ignored) first step in assessing vulnerability across a large area. These inputs can guide both local-level research and also demonstrate the need for region-specific policies to reduce vulnerability and to enhance drought preparedness within dryland farming communities.     

中国沙尘灾害遥感监测研究现状及发展趋势

沙尘灾害及其所引发的次生灾害所造成的生态环境和社会经济问题已越来越引起人类的重视。运用遥感技术进行沙尘灾害监测研究可弥补传统研究手段时空分辨率的不足。本文对遥感在沙尘暴源地、沙尘运移路径变化、下垫面状况、沙尘天气产生的天气背景以及沙尘信息定量提取等几方面的研究进行了简要总结,反映了我国沙尘灾害遥感监测研究的现状,并展望了未来遥感监测沙尘灾害研究的发展趋势。     

Temporal change in the landscape erosion pattern in the Yellow River Basin,China

Using Landsat TM data from 1995 and 2000, changes in the landscape erosion pattern of the Yellow River Basin, China were analysed. The aim was to improve our understanding of soil‐erosion change so that sustainable land use could be established. First, a soil‐erosion intensity index model was developed to study soil‐erosion intensity change in the study area. Over the 5 years, the areas of weak erosion, moderate erosion, severe erosion, and very severe erosion all increased. The area of weak erosion increased dramatically by 7.94×10⁵ ha, and areas of slight erosion and acute erosion decreased by 1.93×10⁶ ha and 4.50×10⁴ ha, respectively. The results show that while the intensity of soil erosion has gradually been decreasing as a whole, in some regions the soil erosion is becoming more severe. Based on landscape indices, the pattern of changes in soil erosion over the past 5 years was analysed. The changes in landscape pattern of soil erosion resulted from human activities. Analysis showed that human impact increases fragmentation, having three major effects on landscape pattern, reduction in patch area, variations in patch shape, and changes in spatial pattern. In the study area, population growth, farming, governmental policy and forest degradation are the major factors causing soil erosion change over a 5‐year period.     

遥感与GIS支持下的榆林地区土地利用动态变化研究

利用1986、1996和2000年人机交互解译的遥感影像资料,采用GIS空间分析技术,通过叠加3个不同时期的土地利用图,分析了榆林地区1986～2000年期间土地利用时空变化特征,同时还分析了榆林地区14年间沙地逆转恢复的情况。结果表明：1986～1996年期间土地利用变化主要表现为：沙地减少了22．25％,草地、林地和城乡居住建设用地分别增加了6．51％、4．63％和3．55％。1996～2000期间,沼泽地、盐碱地分别减少了26．11％、24．39％,沙地仅减少0．79％,草地减少了2．86％,林地仅增加了0．17％,而旱地增加了3．28％。城乡居住建设用地增加了14．13％。14年间沙地面积减少了128684．17hm^2,沙地净逆转为草地118872．99h^2、旱地3605．07hm^2、林地4049．52hm^2。     

柴达木盆地中部盐湖环境遥感初步解译

柴达木盆地是我国主要的盐湖分布区 ,通过美国陆地卫星TM标准假彩色影像图 ,对该盆地中部地的盐湖环境、沙漠分布与变化、地质构造、1 989年洪水的影响范围等自然地质地理特征进行了初步的研究     

Geomorphology, natural hazards, vulnerability and prevention of natural disasters in developing countries

The significance of the prevention of natural disasters is made evident by the commemoration of the International Decade for Natural Disaster Reduction (IDNDR). This paper focuses on the role of geomorphology in the prevention of natural disasters in developing countries, where their impact has devastating consequences. Concepts such as natural hazards, natural disasters and vulnerability have a broad range of definitions; however, the most significant elements are associated with the vulnerability concept. The latter is further explored and considered as a key factor in understanding the occurrence of natural disasters, and consequently, in developing and applying adequate strategies for prevention. Terms such as natural and human vulnerabilities are introduce and explained as target aspects to be taken into account in the reduction of vulnerability and for prevention and mitigation of natural disasters. The importance of the incorporation not only of geomorphological research, but also of geomorphologists in risk assessment and management programs in the poorest countries is emphasized.     

遥感技术在六安市矿山地质环境调查中的应用方法研究

矿山地质环境对于生态环境保护来说尤为敏感,是国土空间生态修复的重要部分,如何快速掌握矿山地物信息的变化是修复、保护和监测的关键所在,本文总结了遥感技术在矿山环境遥感调查的技术方法,结合大别山区矿山环境的特点,突出分析了采场、固体废弃物、地质灾害、恢复治理等矿山地物遥感特征,为六安大别山区国土空间生态修复、自然保护区监测、主体功能区等用途管制提供技术保障和可靠数据。     

西藏盐湖矿产资源遥感定量预测方法研究

西藏自治区地域广大,湖泊众多,盐湖矿产资源十分丰富,但调查研究程度较低,资源潜力不明,家底不清。以遥感信息为基础,采用多因素综合评判模型法进行盐湖矿产定量预测,初步摸清现阶段西藏盐湖矿产资源家底,为地方政府和有关部门进行盐湖矿产资源勘查开发提供了重要参考依据。该预测方法具有较强探索性,和已知查明资源量进行比较,预测结果基本可靠,是西部高海拔地区盐湖矿产资源快速评价的有效方法。     

Satellite based long-term assessment of rangeland condition in semi-arid areas: An example from Botswana

A methodology was devised for comparison of generalised range condition over time, irrespective of the nature of original imagery used. It was applied for range condition change mapping throughout Botswana through 1984-2000. Results showed that range degradation was most widespread during the 1980s drought when 25% of the country was affected, decreased to 6.5% in 1994 and increased to 9.8% in 2000. This suggests that these semi-arid rangelands are fairly resilient and can withstand “normal” droughts even under conditions of heavy grazing pressure. However, degradation that persists during normal or above average rainfall years is related to increasing livestock and other pressures on rangelands and may represent areas with severe range recovery problems. This application meets some requirements of a semi-arid developing country looking to improve range condition monitoring over relatively remote areas.