A quantitative approach for the evaluation of rockfall risk on buildings

Natural Hazards - A quantitative rockfall risk analysis at local scale is a complex and difficult task because it should consider both the randomness in the natural phenomenon and the variability...     

Event tree analysis for rockfall risk assessment along a strategic mountainous transportation route

A quantitative risk analysis has been performed in a tourist area of Sicily (Italy) with the aim of assessing the rockfall risk along an important transportation corridor, crossing a geologically complex area and poor rock masses. The procedure followed herein is based on an event tree analysis, which was properly customized to take into account the peculiarity of the area and of the road path. Rock mass surveys, trajectory simulations and probabilistic models are proposed with the aim of calculating the probability related to possible scenarios in case of rockfalls. Achieved outcomes demonstrate that such procedure, resulting from a multifaceted study, is a reliable tool, which can be taken as reference to calibrate further risk models in comparable contexts of the world, where rockfall threaten communication routes. This would represent a helpful instrument to the scientific community and to local authorities dealing with one of the most troublesome natural phenomena affecting the public safety.     

Empirical assessment of rockfall and debris flow risk along the Karakoram Highway,Pakistan

Natural Hazards - The Karakoram Highway links north Pakistan with southwest China. It passes through unique geomorphological, geological and tectonic setting. This study focused 200-km-long section...     

Uncertainty assessment in quantitative rockfall risk assessment

This study shows a quantitative rockfall risk assessment (QRA) for a slope of the Feifeng Mountain (China), including an explicit assessment of the uncertainties. For rockfall risk analysis, the annual probability of occurrence, reach probability, temporal–spatial probability and vulnerability of tourists were calculated for both dry and rainy day conditions. The resulting individual risk for exposed people visiting the historical site can be considered as acceptable for all scenarios, whereas the overall societal risk lies within the as low as reasonably practicable (ALARP) zone and therefore requires some mitigation actions. For the explicit assessment of uncertainty, an error propagation technique (first-order second moment (FOSM)) was adopted, starting from expert knowledge heuristic estimations of the coefficient of variation for each component of the risk analysis procedure. As a result, coefficients of variation of the calculated risk were obtained, ranging from 48 to 132 %, thus demonstrating the importance of accounting for uncertainty in rockfall risk modelling. A multi-criteria methodology is also proposed for the assessment of the standard deviation of the parameters adopted for the stochastic rockfall run-out model.     

Analysis of rockfall risk on mountainside roads: evaluation of the effect of protection devices

Many kilometres of roads are close to rock slopes that are prone to rockfalls. The fulfilment of safety requirements in such situations is a multidimensional design process involving public and private technicians in the assessment and management of the problem. In this paper, a rockfall risk management approach has been applied to the road infrastructure network of the Regione Autonoma Valle D’Aosta, in order to calculate the level of risk and of its reduction using rockfall protection devices. In order to better understand the methodology, a comparative analysis of road accidents in Aosta Valley has been discussed. The road risk assessment was developed taking into account the absence of rockfall protection devices, and when they are present, different levels of efficacy have been considered.     

油气长输管道滑坡地质灾害危险性评价专家系统研究

以运营的油气长输管道工程为依托,在收集、整理、综合分析既有资料基础上,通过对大量滑坡案例进行分析,明确了滑坡地质灾害的主要诱发因素与稳定性控制指标,建立了滑坡危险性评价指标体系。应用专家系统研究方法,建立油气长输管道线路滑坡地质灾害危险性评价专家系统,并对具体工程进行了地质灾害危险性评估,结果符合实际,可为油气长输管道工程地质灾害减灾防灾提供技术支撑。     

Quantitative assessment of the residual risk in a rockfall protected area

Quantitative Risk Assessment (QRA) has become an indispensable tool for the management of landslide hazard and for planning risk mitigation measures. In this paper we present the evaluation of the rockfall risk at the Solà d’Andorra slope (Andorra Principality) before and after the implementation of risk mitigation works, in particular, the construction of protective fences. To calculate the risk level we have (i) identified the potential rockfall release areas, (ii) obtained the volume distribution of the falling rocks, (iii) determined the frequency of the rockfall events, and (iv) performed trajectographic analysis with a 3D numerical model (Eurobloc) that has provided both the expected travel distances and the kinetic energy of the blocks. The risk level at the developed area located at the foot of the rock cliff has been calculated taking into account the nature of the exposed elements and their vulnerability. In the Forat Negre basin, the most dangerous basin of the Solà d’Andorra, the construction of two lines of rockfall protection fences has reduced the annual probability of loss of life for the most exposed person inside the buildings, from 3.8×10⁻⁴ to 9.1×10⁻⁷ and the societal risk from 1.5×10⁻² of annual probability of loss of life to 1.2×10⁻⁵.     

Frequency of debris flows and rockfall along the Mendoza river valley (Central Andes), Argentina: Associated risk and future scenario

The frequency of debris flows and rockfalls was estimated by temporal distribution of these events during the last 50 years. This parameter was expressed by annual probability of occurrence and mean interval of recurrence of historical events. More recurrent events in this sector of the Central Andes are associated with the Guido locality and tunnels situated along International road No. 7. Furthermore, these events are more frequent in Cordillera Frontal where the mean recurrence interval was lower than in Precordillera. The maximum interval of recurrence is rarely greater than 20 years, showing the activity of these events on human lives and infrastructure in this region. The accuracy of the determined recurrence frequency is discussed. A future scenario indicates that landslides will be probably more frequent under global climate change. As a consequence, those most vulnerable elements in the region, the international access routes, may be severely damaged in the future, implying an adverse impact in our regional economy.     

基于GIS的重点区域地质灾害风险评价

为治理河口拦门沙,实施了通过整治及疏浚的方式打通拦门沙的射阳港双导堤工程,导堤的功能定位为“导流、挡沙、减淤”。通过对江苏盐城射阳港海岸动力地貌等环境的调查,分析研究射阳港区不同时期的水下沉积物分布特征、不同历史时期的水下地形特征,同时研究不同时期的水质、底质沉积物、生态群落等指标数据,对射阳港双导堤建设的环境影响进行后评价。研究认为：双导堤工程完工后导堤口区域出现明显冲刷,导堤两侧出现淤积,颗粒变细,但对水质环境、底质沉积物环境和生态环境的影响不大,双导堤工程建设对环境影响的风险可控。     

Preliminary gas hazard evaluation in Greece

Natural Hazards - Like other geodynamically active areas, Greece is also affected by a large number of geogenic gas manifestations. These occur either in the form of point sources (fumaroles,...     

基于GIS的北京地区泥石流危险度区划

泥石流是北京市山区的主要地质灾害类型之一,文章将北京市以3km×3km的网格进行剖分,选取地形、地层岩性、构造、灾害因子及降水5个因素作为泥石流危险度区划的指标,基于GIS对北京市泥石流危险程度进行了区划。其结果可为北京市开展泥石流预警预报、减灾防灾规划和山区经济建设布局等提供科学参考依据。     

GIS-based multi-dimensional risk assessment of the grassland fire in northern China

This study presents a methodology for risk analysis and assessment to manage grassland fire in northern China based on the Geographical Information Systems from the viewpoints of climatology, geography, disaster science, and environmental science and so on. Using natural disaster and risk assessment theory, a multi-dimensional grassland fire risk index (MGFRI) was proposed by integrating weighted comprehensive method, analytic hierarchy process, and fuzzy gamma method into natural disaster risk index. The developed MGFRI will be an easily understandable tool to manage grassland fire by comparing the risk of regions in the northern China and relative contributions of various factors, for example, hazard, exposure, vulnerability, and management ability. A scale of one to five was derived to measure the risk degree. It shows that 4.4?% of grassland falls in the category of ??very high?? risk, followed by 9.6, 19.1, 60.9, and 5.9?%, respectively, in the categories ??high??, ??middle??, ??low??, and ??very low??. The assessment results show reliability by test. The results in this study are intended to support local, provincial, and national government agencies to: (1) make resource allocation decisions; (2) make high-level planning decisions; and (3) raise public awareness of grassland fire risk, its causes, and ways to manage it.     

基于边坡单元的公路沿线滑坡危险度概率分析

公路沿线发生的滑坡、泥石流等自然灾害是造成交通停滞的主要原因。对公路沿线边坡进行稳定性评价及滑坡灾害分析对于公路管理和灾害防治具有重要意义。为了能对大范围边坡应用三维力学模型进行稳定性评价,研究中将较大研究区域划分为多个边坡单元（slope unit）,并介绍了边坡单元划分方法。对每个边坡单元,采用随机生成许多假想滑动面并通过一个基于GIS的边坡稳定性三维分析模型计算其安全系数的方法,找出具有最小安全系数的危险滑动面,同时求出在试算过程中安全系数小于某临界值（通常设为1.0）的结果出现的比率,作为该边坡单元的滑坡发生概率,以此作为指标对研究区域进行危险度评价。通过对日本49号国道沿线边坡中的应用对该方法的实用性进行了验证。     

基于GIS的丹阳城镇工程建设适宜性评价

为了使城市地质调查成果更好地服务于新型城镇化建设,以正在开展的丹阳城市地质调查项目为依托,分析丹阳市地质环境条件并评价城镇工程建设的适宜性。选取地形地貌、水文、工程地质、水文地质、地质灾害、活动断裂和地震效应7个一级评价因子,地貌分区、水系水域、洪水淹没程度等11个二级评价因子,以500 m×500 m网格为评价单元,利用GIS软件对丹阳市进行工程建设适宜性评价。在此基础上,叠加了丹阳市生态红线管控区,将一级管控区划为工程建设不适宜区,二级管控区划为工程建设适宜性差区。结果表明,除生态管控区外,丹阳市工程建设适宜性总体良好,大部分地区为适宜区,适宜工程建设; 城市开发建设不能突破生态保护红线。     

An integrated GIS-based approach for geohazards risk assessment in coal mines

From the viewpoint of safety in underground coal mining, the most suitable mining panel is the one with minimum geological structures, the right machinery, and equipment selection, trained employee, and proficient stope management. Since the ground parameters are uncontrollable and inherent uncertainties exist, a high percent of risk will usually accompany the underground coal mining activities. The main purpose of this study is to present a geological–geotechnical risk assessment model for identification of high risk-prone areas in underground coal mines using an integrated GIS-geostatistics system. Tabas as the first mechanized and largest underground coal mine in Iran was selected as a case study in this study. Gas content of coal seam, Coal Mine Roof Rating (CMRR), initial in situ stress state, fault throw, and orientation were selected as hazard/risk factors. For estimating the amount of coal seam gas content, CMRR and initial in situ stress in unsampled areas and providing the prediction maps, geostatistics module in ArcGIS was used. Rock engineering system–interaction matrix method was used for attribute weight assignment. Next, the attribute layers were weighted, rated, and overlaid to create a final map of geohazards risk. The analysis results of final risk map indicate that about 45% of under study area is prone to high to very high geohazards risk. Comparison of the results with experiences obtained during the early part of the mine and mined-out panels showed generally good agreement with promising ideas. This highlights the potential application of the GIS-based approach for hazards detection and geohazards risk assessment in underground coal mines.     

Probabilistic GIS-based method for delineation of urban flooding risk hotspots

Identifying urban flooding risk hotspots is one of the first steps in an integrated methodology for urban flood risk assessment and mitigation. This work employs three GIS-based frameworks for identifying urban flooding risk hotspots for residential buildings and urban corridors. This is done by overlaying a map of potentially flood-prone areas [estimated through the topographic wetness index (TWI)], a map of residential areas and urban corridors [extracted from a city-wide assessment of urban morphology types (UMT)], and a geo-spatial census dataset. A maximum likelihood method (MLE) is employed for estimating the threshold used for identifying the flood-prone areas (the TWI threshold) based on the inundation profiles calculated for various return periods within a given spatial window. Furthermore, Bayesian parameter estimation is employed in order to estimate the TWI threshold based on inundation profiles calculated for more than one spatial window. For different statistics of the TWI threshold (e.g. MLE estimate, 16th percentile, 50th percentile), the map of the potentially flood-prone areas is overlaid with the map of urban morphology units, identified as residential and urban corridors, in order to delineate the urban hotspots for both UMT. Moreover, information related to population density is integrated by overlaying geo-spatial census datasets in order to estimate the number of people affected by flooding. Differences in exposure characteristics have been assessed for a range of different residential types. As a demonstration, urban flooding risk hotspots are delineated for different percentiles of the TWI value for the city of Addis Ababa, Ethiopia.     

A GIS-based analysis of constraints on pedestrian tsunami evacuation routes: Cascais case study (Portugal)

Tsunami hazard in coastal areas susceptible to flooding, although reduced (in terms of probability of occurrence), may pose a high risk. Therefore, in these areas, a detailed evacuation planning of the affected population is required as a risk mitigation measure. The knowledge and enforcement of evacuation routes may reduce the population vulnerability, making it more resilient and reducing risk. This paper presents a GIS approach for modelling evacuation routes based on the optimal path search problem, of the graph theory, which is implemented on ArcCasper tool. The methodology proposed considers the elements involved in the evacuation process, the worst credible tsunami inundation scenario (hazard extent and travel time), the number of people that needs to be evacuated in different time scenarios, the safe areas or destination points of the evacuation routes, the roads network characteristics and finally the time available to evacuate. The knowledge of those elements allows predicting some possible outcomes of the evacuation, such as the arrival time of the evacuees to a shelter and the identification of congestion hot spots resulting from the application of a flocking model which simulates the path to be used by evacuees avoiding obstacles. The municipality of Cascais was used to test the methodology proposed in this study. Cascais is one of the largest urban centres located about 25 km west of Lisbon, Portugal, with a high density of infrastructure along the coastline whereby most of the population and economic activities are exposed to a tsunami. The results, presented in the form of maps, allow identifying the optimal evacuation routes as well as the unfeasible routes. This crucial information could be used to the evacuation optimization regarding the location of meeting points and vertical shelters as well as to improve the accessibility of the areas to be evacuated.     

基于GIS技术的皖南地区钨钼矿资源评价与预测

近年来,皖南地区在钨钼矿找矿方面取得了重大突破,具有较大的找矿潜力。应用GIS技术对皖南地区的地质、矿产、物化遥等综合信息建立地学空间数据库,在此基础上综合分析区内各类成矿信息和找矿信息,借助计算机处理各类数据,进行成矿信息空间综合分析,建立评价预测模型。选用证据权法对矽卡岩型、斑岩型和热液型钨钼矿资源进行空间定位评价和预测,在四级成矿远景区内圈定了23个Ⅴ级成矿区和68个重点区块,并对这些重点区块进行分级与评述,为该地区的钨钼矿勘查提供参考。     

Ground reinforced embankments for rockfall protection: design and evaluation of full scale tests

Infrastructures such as roads and railways as well as urbanised areas, in mountainside regions, can frequently be endangered by rockfalls and, therefore, need to be protected against the impact of rolling blocks. Among the various protection works that can be used, ground reinforced embankments can be considered a feasible technique. A set of full-scale tests on embankments made of ground reinforced by geogrids are presented and discussed. The experiments were performed in a specifically designed and constructed test facility, where concrete blocks up to 9,000 kg in weight were thrown onto a geogrid reinforced embankment at a speed of about 30 m/s. Several embankments made of different geogrid types, different soils and construction layouts were tested at different impact energy levels, permitting a quantitative assessment of the resistance impact of these structures. The experimental results were compared with those obtained from a dynamic finite element method numerical model, and a good agreement was obtained.     

基于GIS的人工神经网络模型在地质灾害危险性区划中的应用

地质灾害区域评价和危险性区划结果的准确与否,主要取决于基础地质资料的可靠性及数学模型的合理性.为了提高数据的可靠性,利用GIS,在其支持下管理多源基础地学数据,进行数据处理,提取因素图层,剖分形成评价图元区域.然后在GIS基础上进行二次开发,将人工神经网络模型和GIS有机整合,这样GIS既为人工神经网络模型提供评价数据,又处理其评价结果数据,成图输出.本文遵从上述思路,结合长江三峡示范区(巴东-新滩)具体实例,探讨了人工神经网络和GIS结合(基于GIS的人工神经网络)的可能性和现实途径及其在区域地质灾害危险性区划中的应用前景.这种思路同样也适合其他数学模型与GIS的结合.