Preventing and Limiting Exposure to Geo-Hazards:Some Lessons from Two Mountain Villages Destroyed by the Wenchuan Earthquake

This paper examines the experiences of two mountain communities- Yinchanggou and Donghekou in the Wenchuan earthquake of May 12, 2008, where Yinchanggou's tourism economy and natural park system was destroyed and Donghekou was buried by a landslide. We conducted research surveys on both the communities, interviewing survivors and local officials, and observed the destruction/reconstruction, geological, and living conditions. We suggest that protracted educational processes be put into place so that mountain communities possess a knowledge base to consider long-term disaster prevention when building the economy in the fragile and geo-hazardous conditions of the Longmenshan. The Donghekou Earthquake Ruins Park is an exemplar of turning disaster into sustainable, safe development for small mountain villages.

Early warning for geo-hazards based on the weather condition in China

According to national early warning practice for geo-hazards from 2003 to 2005,it is systematically concluded that the basic characteristics of geo-hazards,early warning method and forecast result based on the geological maps of China in a scale 1∶6 000 000.With the contrast of different characters between sustained rainfall and typhoon rainfall inducing geo-hazards,the disaster reduction result and some problems are preliminarily analyzed.Some basic recognition is that early warning to geo-hazards is feasible,national scale forecast is only to call attention,but can't immediately be used to disaster reduction decision-making.And,the future direction is to build a united disaster reduction framework of early warning system including national,provincial and county levels based on weather factors in different scale of area.

ArcGIS-based evaluation of geo-hazards at Yaozhou County,Shaanxi,China

In conventional susceptibility evaluation of geo-hazards,there are some limits,such as unreasonable division of evaluated region,difficulty in quantifying evaluation indicators,time-consuming calculation.To address these problems,we try to employ the software ArcGIS to evaluate geo-hazards susceptibility.The study area of Yaozhou County is automatically divided into 3562 units.Based on the spatial overlay analysis function of ArcGIS,quantitative evaluation of geo-hazards susceptibility is implemented in the study area,and the geo-hazards susceptibility zoning is mapped.It is observed that the evaluation results match well with field investigations.

Risk analysis system of geo-hazard based on GIS technique

The socio-economic attribute of geo-hazard made us distinguish it from the traditional engineering geology study. It will get more social benefit from the analysis of the geo-hazard in the socio-economic attribute. The hazard and the vulnerability of the element controls the risk level of the regional geo-hazard. The risk analysis supported by GIS in geo-hazard study is one of the most important directions. Based on the author’s studies in recent years, a risk analysis system of regional geo-hazard (RiskAnly) has been developed on the basis of software MAPGIS. The paper introduces the train of system design, the structure and the workflow of RiskAnly. As a case study, the paper also deals with the risk zonation of the regional landslide hazard of China.

基于格网GIS与灰色关联模型的崩滑流灾害孕灾环境研究

以吉林省长白朝鲜族自治县为研究区域,将致灾因子属性纳入到崩滑流孕灾环境评价中,并结合地形地貌、人类活动强度、岩土体结构与地质构造、水文条件、植被状况等构建了指标体系。利用灰色关联模型分析了研究区的孕灾环境,研究结果表明:①区域内崩塌、滑坡、泥石流等地质灾害孕灾环境具有空间集聚性,复杂区域主要集中在临长、长松公路、沿江公路及乡道,少部分分布在村屯和重要设施附近;②将格网区域内的崩塌、滑坡、泥石流的种类、个数和规模做为评价孕灾环境的指标比较合理;③区域内公路沿线,以及矿区周边地质灾害孕灾环境十分复杂,说明人类活动强度是构成本区域地质灾害的主要因素;④根据区域实际情况与本次分析结果比对,发现灰色关联模型能很好地用于地质灾害孕灾环境评估。

Quantitative Zoning Assessment of Crustal Stability Along the Yunnan-Tibet Railway Line,Western China

The planned Yunnan-Tibet railway goes through the northwest of Yunnan Province and the southeast of the Tibet Autonomous Region. Because of its location near the collision belt of the Eurasian and Indian plates, complex engineering geological conditions and difficult engineering geological problems are encountered. The study is aimed at making the zoning assessment of crustal stability along the railway line so as to provide a better base for its construction, especially its line selection. For this purpose, the following seven influencing factors of crustal stability were selected and quantified by grading and scoring： active fault, seismic activity, geo-stress field, geo-strain field, geothermal field, geo-hazard, and lithologic character. Of these factors, the active fault, seismic activity and geo-hazard are the three most prominent factors influencing the railway construction. Along the railway line there are 1731703 calculation units to be divided. The zoning assessment calculation was completed by ArcGIS-based information fusion method. The assessment results aid railway line selection and show that there are 10 stable sectors, 28 relatively stable sectors, 23 relatively unstable sectors, and 20 unstable sectors along the Yunnan-Tibet railway line.

Slope stability hazard management systems

Weather-related geo-hazards are a major concern for both natural slopes and man-made slopes and embankments. Government agencies and private companies are increasingly required to ensure that there is adequate protection of sloping sur- faces in order that interaction with the climate does not produce instability. Superior theoretical formulations and computer tools are now available to address engineering design issues related to the near ground surface soil-atmospheric interactions. An ex- ample is given in this paper that illustrates the consequences of not paying adequate attention to the hazards of slope stability prior to the construction of a highway in South America. On the other hand, examples are given from Hong Kong and China's Mainland where significant benefits are derived from putting in place a hazard slope stability management system. Some results from a hazard management slope stability study related to the railway system in Canada are also reported. The study took advantage of recent research on unsaturated soil behaviour and applied this information to real-time modelling of climatic conditions. The quantification of the water balance at the ground surface, and subsequent infiltration, is used as the primary tool for hazard level assessment. The suggested hazard model can be applied at either specific high risk locations or in a more general, broad-based manner over large areas. A more thorough understanding of unsaturated soil behaviour as it applies to near ground surface soils, along with the numerical computational power of the computer has made it possible for new approaches to be used in slope hazard management engineering.

Geospatial Modeling for Sinkholes Hazard Map Based on GIS &RS Data

The Kinta Valley is an area of karst in the north-western part of Peninsular Malaysia. Over 30 years of uncontrolled land use and development has led to significant changes in topography and geomorphology, such as the appearance of sinkholes. In this paper, geospatial techniques were utilized to the task of evaluating sinkholes susceptibility map using a spatial multi criteria evaluation approach (SMCE). Sinkhole location and a spatial database were applied to calculate eight inherent causative factors for limestone instability namely: lithology, structure (lineament), soil cover, slope, land use mining, urban area features, ponds and rivers. The preparation of the sinkhole geohazard map involved summing the weighted values for each hazard element, which permits the construction of geohazard model;the results of the analysis were validated using the previous actual sinkholes locations in the study area. The spatial distribution of sinkholes occurrence, urban development, faults distribution and ex-mining ponds are factors that are directly responsible for all sinkholes subsidence hazards. Further, the resulting geo-hazard map shows that 93% of recent sinkholes occur in areas where the model flags as “high” and “very high” potential hazard, located in the urbanized part of the valley, while less-developed areas to the west and southwest suffered less sinkhole development. The results can be used for hazard prevention and land-use planning.

Evaluation of Geological Hazards for Landuse Planning in Nabq Protectorate, Southeastern Sinai Using GIS Techniques

Nabq protectorate is one of wonderful natural places in Egypt. It is characterized by diversity of bio-lives such as mangrove forests, coral colonies, wild life plants and migratory birds. Ongoing growth of tourism industries at Sharm El Sheikh northward into the Nabq protectorate causes severe hazards on its natural resources. The aim of the present study is to assess the present geo-environmental hazards in the Nabq protectorate. Assessment includes the analysis of satellite images, topographical, geological and other ancillary geological data using GIS technology. GIS data analyses indicate that the area is under threat from some of geo-hazards. Rough topography and mass wasting with high probability of flash flooding threaten different constructions in this area. The mobilization of coastal sand dunes, wave action and tidal currents are natural impacts on Nabq ecosystems, where moved dunes leave clay soils that are removed in some places by tropical storms increasing sea water turbidity that threaten the corals and other living organisms in the tidal flat region. The seismic activity hazard in the study area is usually active on lineaments extending parallel to the trend of the Gulf of Aqaba-Dead Sea transform fault where the Nabq protectorate occupies its southern segment. Unwise planning activities destroy the natural environmental resources in Nabq area by construction of new resorts on mangrove forests, coral colonies and raised beaches. Hazard assessment identifies land suitability and land use maps that are clearly exhibit models of traditional dams and buffer strips on coastal zone and highways as well as around the Bedouin communities which are worked on tourism and fishing. These maps are urgent in need of an assessment and rehabilitation program to mitigate geo-hazard.

Experimental Field Study of Movement Charateristics of Rock Blocks Falling down a Slope

The downslope movement of detached rock blocks along steep slopes is an important process endangering the safety of infrastructure along the foot of a slope and on the valley bottom,but only limited knowledge is available on the influence of various factors on the velocity and distance of movement of such blocks.We discuss the influence of the mass and shape of the rock blocks,the steepness of the slope,and the thickness of the overburden on the slope,on the distance of movement of rock blocks which was observed in 256 field experiments with differently shaped blocks from 3 different positions on the slope with a height of 176 m.The statistical evaluation of the results of the field tests shows that the slope condition of gradient and overburden is the main factor,the form of rock masses is the second factor,and the mass is the third of the influencing factors.It is the maximum average acceleration for movement of rock masses when the mass of rock masses is 15≤m27 kg,the form of rock masses is flake,the condition of gradient is on average 59.6° and the overburden is basic exposed bedrock and a small quantity of gravel-soil in the experiment condition.It is the minimum average acceleration for movement of rock masses when the mass of rock masses is 9.5≤m15 kg,the form of rock masses is rectangular,the condition of gradient is on average 39° and the overburden is gravel-soil and cinder.Then,the foundation for impact energy is provided and the new feasible methods to prevent potential unstable rock masses are put forward.