华南坡地灾害的形成与发生规律

本文以广东清远"97.5.8”飞来寺泥石流重灾、德庆县花岗岩区坡面侵蚀与崩塌、国道321和324线广东西段近80个边坡变形破坏为例,分析研究了华南坡地灾害的形成与分布规律.73%的坡地灾害发生于山体南坡或东南坡.究其原因,有以下几点认识:(1)华南地区的区域地质构造,以新华夏系NE-SW走向最为典型,同时派生了次一级的NW-SE走向的构造形迹也十分明显.构造裂隙发育,风化壳深厚,在外力作用下斜坡沿裂隙失稳变形.(2)山体北坡岩体的风化作用比南坡弱,南坡昼夜及季节的温差和湿度比北坡大,而且是迎风坡,风化壳相对深厚.(3)华南地区夏秋两季台风暴雨频繁,据20余年的气象资料统计,南风、东南风占61%,暴风伴雨而来,而且强度大,为向南边坡带来不稳定因素.华南地区的斜坡崩塌或滑坡以及泥石流灾害,南坡、东南坡比其它方位数量大,程度严重,具有明显的方向性和规律性.

坡地灾害与重庆城市建设

阐述和探索了重庆地区斜坡的形态和物质结构特征，以及在人为切坡活动的影响下与坡地灾害的形成关系。

台湾屏东县狮子乡坡地灾害潜势分析

以屏东县狮子乡为例,利用GIS探讨近年来致灾降雨事件之特性及空间分布趋势,并配合崩塌潜势与土石流(即泥石流,编者注)潜势溪流范围。首先将筛选出之地文因子,以曼-惠特尼进行崩塌相关性验证,具相关性之因子再以不安定(即不稳定)指数法计算出权重,并求得影响崩塌之主要因子;对于土石流潜势溪流之危险度并不予以评估,仅说明其集水区之地文特性;然后绘制崩塌潜感图,最后配合致灾降雨事件之日最大降雨量频率分析、特性与主要降雨空间分布进行灾害潜势分析,提供疏散避难发布决策之先后顺序。期望藉由分析坡地灾害潜势,能够达防灾、减灾之功效。

坡地地质灾害的减灾策略——以降雨预警基准为例

降雨是诱发坡地地质灾害的重要原因,因此掌握降雨的趋势与分布规律,可有效地用于坡地灾害预警,但由于降雨预测精度、灾害资料统计的不足与坡地地质条件的不确定性,实际应用降雨预警基准仍存在许多困难。通过分析台风诱发坡地地质灾害的降雨特性,来说明降雨预警基准在防灾减灾工作上应用的条件与限制。结果表明,对于不同类型之坡地灾害与降雨分布特性,需采用不同的雨量预警基准。唯有通过岩土力学、工程地质学与气象学的整合研究,才能有效提高降雨预警基准预测的准确率,因此各学科的整合是未来防灾减灾研究工作的发展趋势。

国外城市的减灾法规

国外城市的减灾法规刁承泰（西南师范大学地理系）城市是一地区的政治和经济中心，是减灾防灾工作的重点。在城市管理中，不但要调查和分析各种城市灾害信息，而且要重视减灾法规的制订与实施。目前，我国城市已有一些减灾法规，但还很不完善。本文简要介绍国外城市对某些...

Landslide disaster in the loess area of China

China is the country with most widely distributed loess area in the world, and its loess area accounts of 6.63% of total nation land area. The landslide disaster occurs frequently for complex natural condition and becomes major factors hindering the social and economic development of loess regions. Through different indexes, the authors divided the landslides into 9 principal types and analyzed the distribution characteristics of loess landslide in time and space, the affecting factors and mechanism of landslides. It is pointed out that time and spatial distributions of landslides are closely correlative to topographic and geomorphic conditions, earthquake and rainfall, and the key influencing factors include topography, geomorphology, new tectonic movements, earthquake activity, surface water, ground water and human activities. The authors emphasized that the natural condition of loess areas was favorable to landslides, human activities impelled its occurrence and that controlling the loess landslide was an urgent task for sustainable development in the loess zone.

Investigation and Assessment of Landslides and Debris Flows in Sichuan Province of China by Remote Sensing Technique

Taking TM images, ETM images, SPOT images, aerial photos and other remote sensing data as fundamental sources, this research makes a thorough investigation on landslides and debris flows in Sichuan Province, China, using the method of manual interpretation and taking topography maps as references after the processes of terrain correction, spectral matching, and image mosaic. And then, the spatial characteristics of landslides and debris flows in the year of 2005 are assessed and made into figures. The environmental factors which induce landslides and debris flows such as slope, vegetation coverage, lithology, rainfall and so on are obtained by GIS spatial analysis method. Finally, the rela- tionships of landslides or debris flows with some environmental factors are analyzed based on the grade of each envi- ronmental factor. The results indicate: 1) The landslides and debris flows are mainly in the eastern and southern area of Sichuan Province, however, there are few landslides and debris flows in the western particularly the northwestern Si- chuan. 2) The landslides and debris flows of Sichuan Province are mostly located in the regions with small slope degree. The occurring rate of debris flow reduces with the increase of the vegetation coverage degree, but the vegetation cov- erage degree has little to do with the occurrence of landslide. The more rainfall a place has, the easier the landslides and debris flows take place.

Susceptibility Assessment of Landslides Caused by the Wenchuan Earthquake Using a Logistic Regression Model

The Wenchuan earthquake on May 12,2008 caused numerous collapses,landslides,barrier lakes,and debris flows.Landslide susceptibility mapping is important for evaluation of environmental capacity and also as a guide for post-earthquake reconstruction.In this paper,a logistic regression model was developed within the framework of GIS to map landslide susceptibility.Qingchuan County,a heavily affected area,was selected for the study.Distribution of landslides was prepared by interpretation of multi-temporal and multi-resolution remote sensing images(ADS40 aerial imagery,SPOT5 imagery and TM imagery,etc.) and field surveys.The Certainly Factor method was used to find the influencial factors,indicating that lithologic groups,distance from major faults,slope angle,profile curvature,and altitude are the dominant factors influencing landslides.The weight of each factor was determined using a binomial logistic regression model.Landslide susceptibility mapping was based on spatial overlay analysis and divided into five classes.Major faults have the most significant impact,and landslides will occur most likely in areas near the faults.Onethird of the area has a high or very high susceptibility,located in the northeast,south and southwest,including 65.3% of all landslides coincident with the earthquake.The susceptibility map can reveal the likelihood of future failures,and it will be useful for planners during the rebuilding process and for future zoning issues.

Risk Assessment of Disaster Chain: Experience from Wenchuan Earthquake-induced Landslides in China

This paper deals with the formative process of the Wenchuan earthquake disaster chain risk. Selected earthquake-landslides chain risk is critically evaluated by the probability of landslide displacement failure based on the Newmark's permanent-deformation model. In this context, a conceptual model of regional disaster chain risk assessment was proposed, in which the hazardformative environments sensitivity was the core factor as well as the main difference compared with single disaster risk assessment. The disaster chain risk is accumulation of primary disaster risk and the secondary disasters risks. Results derived from the Wenchuan case proved that the conceptual model was suitable for the disaster chain risk assessment, especially the sudden disaster chain. This experience would offer greater potential in application of conceptual model of disaster chain risk assessment, in the process of large-scale disaster risk governance.

Landslide risk perception and communication for disaster risk management in mountain areas of developing countries：a Mexican foretaste

The increasing impact of disasters at local,national,regional and global scales in recent decades has provided enough evidence to urgently direct attention towards the necessity of disaster risk reduction and management,and this requires knowledge.Knowledge without communication is barren,and to communicate the risk of disaster it is necessary to understand the perception of the people at risk.In particular,this paper deals with the necessity to delineate strategies of risk communication in pursuance of risk knowledge as a core of disaster risk reduction and management,especially in mountain areas of developing countries.To portray this issue,an analysis of landslide risk perception in terms of experience,landslide risk awareness,exposure,preparedness,and risk communication and trust was undertaken in the municipality of Teziutlán,Puebla,Mexico,an area that has been affected for several decades by episodes of mass movement.Analysis of the responses to a risk perception questionnaire has offered valuable insights in terms of the information and knowledge most required by the people living in the area of interest,in order to devise a realistic and functional strategy to communicate the risk of a landslide disaster.This includes better understanding of controlling factorsand drivers of this risk,and the establishment of potential trusted sources of risk communication.Beyond considering practical matters of risk assessment and management,risk perception and communication can increase the resilience of vulnerable people,and can enhance capacity building for present and future generations.

Engineering geological conditions and features of geologic hazards in Wudongde reservoir of Jinshajiang River valley

There is a great difference between the distribution and evolvement characteristics of slope geological hazard in the same geographical location and climatic conditions,taking the similar structural-genetic connection in Wudongde reservoir area of Jinshajiang River valley for example. In all engineering geological conditions,the chronologic age and attitude of strata,and the lithologic association factors control the distributions and evolvement characteristics of slope geological hazard in the studied area. The study shows that the slopes in geological evolution are in different stages. The conclusion helps to understand the types and the intensity of geological disasters.

Landslide Hazard Mapping During a Large Scale Earthquake

This paper reports a method to make hazard maps of sediment disasters resulting from an earthquake and following heavy rainfall for the entire region of Gunma prefecture, Japan. Firstly, we identified the slopes in the study area, which are susceptible to large-scale landslides and land failures during an earthquake with a magnitude of seven on the Richter scale. To analyze the sheer volume of the data, we employed a statistical method to evaluate the susceptibility, mainly considering geomorphologic conditions. Secondly, we extracted mudflow and slope failure susceptible areas and potential flooding zones resulting from a damming at a river triggered by the earthquake and heavy rainfall, and we identified the settlements which would be isolated by the road disruption caused by the sediment disasters. As the result, 359 settlements were classified as potential isolation areas. Combining the above-mentioned susceptibility maps, we obtained two types of sediment disaster hazard maps of the study area, depicting the potential hazards which would occur during the earthquake and the disasters which would be caused by heavy rainfall following the quake, respectively. These hazard maps and the disaster information would be useful for the regional disaster prevention planning and countermeasures in the future.

Landslide hazards mapping using uncertain Na?ve Bayesian classification method

Landslide hazard mapping is a fundamental tool for disaster management activities in Loess terrains. Aiming at major issues with these landslide hazard assessment methods based on Naive Bayesian classification technique, which is difficult in quantifying those uncertain triggering factors, the main purpose of this work is to evaluate the predictive power of landslide spatial models based on uncertain Naive Bayesian classification method in Baota district of Yan＇an city in Shaanxi province, China. Firstly, thematic maps representing various factors that are related to landslide activity were generated. Secondly, by using field data and GIS techniques, a landslide hazard map was performed. To improve the accuracy of the resulting landslide hazard map, the strategies were designed, which quantified the uncertain triggering factor to design landslide spatial models based on uncertain Naive Bayesian classification method named NBU algorithm. The accuracies of the area under relative operating characteristics curves（AUC） in NBU and Naive Bayesian algorithm are 87.29% and 82.47% respectively. Thus, NBU algorithm can be used efficiently for landslide hazard analysis and might be widely used for the prediction of various spatial events based on uncertain classification technique.

Landslide Disaster Vulnerability in Western Kenya and Mitigation Options： A Synopsis of Evidence and Issues of Kuvasali Landslide

The Kuvasali landslide disaster in Malava, Western Kenya, which caused harmful geo-environmental hazards to the villagers in August 2007, formed the premise of this paper. The existing landslide vulnerability occurrence ratings have been identified and documented using participatory approaches to ascertain the adoptive indigenous methods, which helped mitigation against the negative impacts by determining the slope steepness using Abney level. The geological set up, settlement and climatic factors, relating to landslides, revealed that the affected homesteads were on a steep slope of approximately 70%, with underlying metamorphosed basement rocks comprising ofgneisses, schists and granite intrusions. The steep escarpment overlying these rocks, where the landslide occurred, consists of volcanic rocks and black cotton clayey soils. The slope has scattered vegetation cover due to farming, while the low-lying area is planted with sugar cane and maize plantations. The landslide disaster led to loss of lives, injuries and damage to property. Natural resources, including water points, suffered siltation. Mitigation measures such as geo-hazard mapping and zoning, awareness training and campaigns for the local people focusing on hazard-prone areas resulting from poor land use practices have been recommended.

Geospatial susceptibility mapping of earthquake-induced landslides in Nuweiba area, Gulf of Aqaba, Egypt

Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the earthquake-induced landslide susceptibility in Nuweiba area in Egypt with considerations of geological, geomorphological, topographical, and seismological factors. An integrated approach of remote sensing and GIS technologies were applied for that target. Several data sources including Terra SAR-X and SPOT 5 satellite imagery, topographic maps, field data, and other geospatial resources were used to model landslide susceptibility. These data were used specifically to produce important thematic layers contributing to landslide occurrences in the region. A rating scheme was developed to assign ranks for the thematic layers and weights for their classes based on their contribution in landslide susceptibility. The ranks and weights were defined based on the knowledge from field survey and authors experiences related to the study area. The landslide susceptibility map delineates the hazard zones to three relative classes of susceptibility: high, moderate, and low. Therefore, the current approach provides a way to assess landslide hazards and serves for geo-hazard planning and prediction in Nuweiba area.

Potential of GIS Evaluation for Mass Wasting Processes in Mountain Ranges of South West Coast of India

The aim of the study is to monitor and assess landslide hazards by remote sensing data processing and GIS （Geographic Information Service） spatial analysis. Idukki district, the western Ghats of India was chosen as test area, because of frequent destructive mass wasting processes. Western Ghats is a prominent orographic feature that runs parallel to the south west coast of India. Predicting landslide hazard on a regional scale, namely the assessment of actual and potential mass movement over large area is carried out using Remote Sensing and GIS. A numerical weightage to the causative factors of slope instability such as slope, relative relief, aspect, curvature, drainage density, drainage frequency, land use, road buffer and drainage buffer are assigned as per earlier workers for the purpose of landslide susceptibility zonation. A high degree of match is found between observed and predicted landslide hazard by the procedure employed in the study.