泥石流危险度野外快速评价方法探讨

文章系统地总结和分析了当前比较常用的泥石流危险度评价的研究方法,指出现行泥石流危险度评价中评价因子的提取往往需要详细野外勘查,工作量大、费用高,不便于对众多泥石流沟的普查;并提出一种在现场踏勘基础上,基于泥石流规模、频率和承灾体特征的快速便捷的新方法——泥石流危险度野外快速评价,并结合其他方法进行了实例对比验证。结果表明：泥石流危险度野外快速评价结果可靠,可作为快速评价泥石流危险性的新方法进行推广应用。     

支持向量机在泥石流危险度评价中的应用研究

为改善传统泥石流危险度评价方法存在的缺陷,提出了基于支持向量机的泥石流危险度评价方法,并建立了支持向量机评价模型。研究选取泥石流一次(可能)最大冲出量(L1)、泥石流发生频率(L2)、流域面积(S1)、主沟长度(S2)、流域最大相对高差(S3)、流域切割密度(S6)和泥沙补给段长度比(S9)7个因子作为泥石流沟谷危险度评价因子,运用支持向量机理论,选用径向基(RBF)核函数,采取"试错法"进行参数优选;确定参数C=8,γ=2。以云南省37条泥石流沟的259个基础数据为样本进行学习训练和测试,建立了泥石流危险度评价的支持向量机模型。并将该模型应用于黄河积石峡水电站库区的泥石流危险性评价中进行验证。将模型评判结果和模糊数学方法的评价结果进行对比分析,结果的一致性达到73.33%。研究认为支持向量机方法能够成功地应用到泥石流危险度评价中,且具有较高的精度及很强的泛化能力,应用前景广阔。     

Neural network modeling for regional hazard assessment of debris flow in Lake Qionghai Watershed, China

This paper presents a neural network (NN) based model to assess the regional hazard degree of debris flows in Lake Qionghai Watershed, China. The NN model was used as an alternative for the more conventional linear model MFCAM (multi-factor composite assessment model) in order to effectively handle the nonlinearity and uncertainty inherent in the debris flow hazard analysis. The NN model was configured using a three layer structure with eight input nodes and one output node, and the number of nodes in the hidden layer was determined through an iterative process of varying the number of nodes in the hidden layer until an optimal performance was achieved. The eight variables used to represent the eight input nodes include density of debris flow gully, degree of weathering of rocks, active fault density, area percentage of slope land greater than 25° of the total land (APL25), frequency of flooding hazards, average covariance of monthly precipitation by 10 years (ACMP10), average days with rainfall >25 mm by 10 years (25D10Y), and percentage of cultivated land with slope land greater than 25° of the total cultivated land (PCL25). The output node represents the hazard-degree ranks (HDR). The model was trained with the 35 sets of data obtained from previous researches reported in literatures, and an explicit uncertainty analysis was undertaken to address the uncertainty in model training and prediction. Before the NN model is extrapolated to Lake Qionghai Watershed, a validation case, different from the above data, is conducted. In addition, the performances of the NN model and the MFCAM were compared. The NN model predicted that the HDRs of the five sub-watersheds in the Lake Qionghai Watershed were IV, IV, III, III, and IV–V, indicating that the study area covers normal hazard and severe hazard areas. Based on the NN model results, debris flow management and economic development strategies in the study are proposed for each sub-watershed.     

澜沧江结义坡沟泥石流灾害评价

为查明坝址区是否存在泥石流地质灾害,分析其对建坝的影响,现场对结义坡泥石流沟进行了追踪调查,以充分认识沟谷的地形地貌条件、地质条件、植被发育情况以及泥石流的活动痕迹、冲淤特征等。并对泥石流沟谷、堆积扇等进行了有关的试验及量测工作。用国内外常用的计算稀性泥石流参数的公式对泥石流的流速、流量及冲击力等参数进行了计算,为正确评价泥石流地质灾害奠定基础。调查研究表明,结义坡沟泥石流活动正处于停歇期,但应注意加强集水区内水土保持工作,尤其是对结义坡沟入口段裸露坡体要引起重视。     

城市泥石流风险评价探讨

探讨了城市泥石流风险评价的系统方法,该方法包括泥石流扇形地危险区划、城市易损性分析和城市泥石流风险评价三个主要内容。泥石流堆积扇危险区划是基于数值模拟计算出的泥深和流速分布图进行叠合完成的。以美国高分辨率的“快鸟”卫星影像为数据源,完成了研究区的城市土地覆盖类型遥感解译,在此基础上完成了城市泥石流易损性分析,应用地理信息系统提供的统计和分析工具,完成了研究区泥石流风险评价。该风险区划图可用于指导对泥石流易泛区的不同风险地带的土地利用进行规划和决策,从而达到规避和减轻灾害的目的,也为生活在泥石流危险区的城市居民提供有关灾害风险信息,以作避难和灾害防治的依据。     

基于模糊数学的地质灾害危险性评价

陕西省引汉济渭工程跨越秦岭构造剥蚀山地和断陷盆地,地质环境条件差,发育地质灾害点72处。选取地质环境条件、地质灾害发育现状和地质灾害预测为评价指标,分别赋予隶属度值;将工程剖分为284个评价单元,采用模糊数学综合评判法计算每个单元的隶属度值,确定危险性小的单元255个,危险性中等的单元29个;说明工程主要位于危险性小的区段。     

区域泥石流危险度评价研究进展

评述了自20世纪80年代末我国开展泥石流危险度评价研究以来,两个主要不同时期的区域泥石流危险度评价方法及其发展过程.详述了我国现行的区域泥石流危险度评价技术及其改进的评价因子转换赋值新方法.现行的区域泥石流危险度评价方法于1995年提出,是以不同的行政区划为基本单元来进行的.评价因子包括主要因子泥石流分布密度,次要因子岩石风化程度系数、断裂带密度、≥25°坡地面积百分比、洪灾发生频率、月降雨量变差系数、年雨量平均≥25mm大雨日数和坡度≥25°坡耕地面积百分比.区域泥石流危险度表达为以上8个因子极差变换后的赋值与其相应的权重乘积之和.这一评价公式,加强了主要因子的作用.主要因子的权重系数上升到33%时则使区域泥石流危险度评价可用一个简单的数学公式来表达.得出的危险度数值已经标准化,取值范围介于0～1之间.这一评价方法的不足之处是得出的危险度数值只有相对意义而不具有绝对意义.在最新的区域泥石流危险度评价研究中,通过分段函数赋值的新方法克服了上述不足.分段函数赋值是基于以下的假定当评价因子超过和等于某一上限值时赋值为1;等于下限值时赋值为0;处于中间值的赋值为0.5.以这3个数值为控制点,假定在每2个点之间,赋值呈线性变化.当中间点为上、下2点之平均值时为双线性模型;当中间点不为上、下限2点之平均值时为三线性模型.根据我国西南地区已有资料的统计,得出了区域泥石流危险度8项评价因子的分段赋值函数.通过2种不同赋值方法在四川凉山州和阿坝州区域泥石流危险度评价中计算结果的比较,从绝对数值来看,分段函数赋值得出的危险度高于极差变换得出的危险度.对于泥石流危险度分析来说,相对偏大的保守估计更为可取.从相对数值来看,两者都具有相同的变化趋势.说明分段函数赋值计算出的区域泥石流危险度既能在同一区域内进行比较,也能在不同区域间进行比较,达到了改进的目的.现阶段我国正在使用的区域泥石流危险度多因子综合评价模型仍然属于经验模型的范畴.它是在经验的基础上采用推理和统计的方法建立的一种评价模型.我们的最终目标是在科学假定和合理简化的基础上,用代表泥石流危险度的2个本质的特征参数泥石流规模和发生频率来建立起区域泥石流危险度的理论模型,并用量化的数学公式来表达.因此,泥石流规模和发生频率相互关系的研究是实现这一目标的突破点.也是今后区域泥石流危险度评价研究的重点所在.     

层次分析法在单沟泥石流危险度评价中的应用

单沟泥石流危险度评价是泥石流危险性评价中的重要内容,对实现山区的安全减灾有着重要意义。文章从系统理论出发,运用层次分析法(AHP)对影响泥石流沟谷危险度的相关因子进行分析,构建单沟泥石流危险度评价的层次指标系统,并对各参与评价因子的权重作了计算,建立起单沟泥石流危险度评价模型。通过对泥石流沟的实例验证,评价结果与实际情况有较好的一致性。该方法将定量与定性相结合,能很好地解决泥石流危险度综合评价问题,对提高泥石流危险度评价的可靠性、准确性及客观性有一定的实践意义。     

区域泥石流灾害的定量风险分析

概述了区域泥石流灾害的风险分析体系,指出了过去区域泥石流灾害危险性研究中的某些误区以及区域社会经济易损性评价的难点。借助于“灾害熵”的概念,提出了区域泥石流灾害危险性定量分析的一种新方法。通过将泥石流灾害的危险性和区域社会经济易损性进行分级,建立了风险评价矩阵。在此基础上,对区域泥石流灾害的风险进行了分级,可为有效地进行区域泥石流灾害的预警,以及为减灾防灾奠定了坚实的基础。     

四川松潘水沟墩沟泥石流成因和动力学特征及其对铁路工程的影响评价

泥石流是山区常见的地质灾害之一,具有运动快速、暴发突然、能量巨大等特点。本文根据现场调查。分析了水沟墩沟泥石流形成条件、流域特征,计算了泥石流的容重、流速、流量、冲出量、淤积厚度等动力学参数,并对其危险性做了定量评价．总结了水沟墩沟泥石流对铁路工程危害模式“先冲-又淤-再冲”。提出了对水沟墩沟泥石流采用相关的减灾防灾措施,供铁路部门制定相应的泥石流防止对策,有益于对成兰铁路线的长远安全运行和服务提供科学保障。     

Recognition of debris flow,debris flood and flood hazard through watershed morphometrics

Debris flows, debris floods and floods in mountainous areas are responsible for loss of life and damage to infrastructure, making it important to recognize these hazards in the early stage of planning land developments. Detailed terrain information is seldom available and basic watershed morphometrics must be used for hazard identification. An existing model uses watershed area and relief (the Melton ratio) to differentiate watersheds prone to flooding from those subject to debris flows and debris floods. However, the hazards related to debris flows and debris floods are not the same, requiring further differentiation. Here, we demonstrate that a model using watershed length combined with the Melton ratio can be used to differentiate debris-flow and debris-flood prone watersheds. This model was tested on 65 alluvial and colluvial fans in west central British Columbia, Canada, that were examined in the field. The model correctly identified 92% of the debris-flow, 83% of the debris-flood, and 88% of the flood watersheds. With adaptation for different regional conditions, the use of basic watershed morphometrics could assist land managers, scientists, and engineers with the identification of hydrogeomorphic hazards on fans elsewhere.     

四川省泸定县深家沟泥石流特征及危险度评价

2006年7月14日泸定县深家沟暴发了一场灾害性泥石流,平均流速6.3m/s,由于泥石流位于县城,造成了较为严重的财产损失.流域面积小、坡陡、沟道短且比降较大是深家沟的主要特征.深家沟属于中度危险的泥石流沟,该沟一次泥石流最大堆积危险范围10633m2,最大堆积长度为147m,最大堆积厚度为1.45m.其防灾减灾措施主要是植树造林,拦挡排导,提高下游的排导能力.     

昆明市东川城区泥石流危险度评价

泥石流是昆明东川城区最主要的地质灾害之一,严重阻碍了城市的社会经济发展。开展东川城区泥石流危险度评价对城市安全与稳定有着重要的意义。文章从地貌学侵蚀旋回理论出发,运用斯特拉勒面积-高程分析法对东川城区后山的3条泥石流沟的危险度进行评价研究。结果表明,深沟和石羊沟的斯特拉勒面积-高程值分别为0.580和0.520,泥石流沟谷正由发育的中年末期向老年期演化,泥石流危险度较低;尼拉姑沟的斯特拉勒面积-高程值为0.452,处于沟谷发育的旺盛时期,泥石流危险度较高,计算结果与当地实际情况有较好的一致性。     

Area-scale landslide hazard and risk assessment

The paper deals with a methodology for quantitative landslide hazard and risk assessments over wide-scale areas. The approach was designed to fulfil the following requirements: (1) rapid investigation of large study areas; (2) use of elementary information, in order to satisfy the first requirement and to ensure validation, repetition and real time updating of the assessments every time new data are available; (3) computation of the landslide frequency of occurrence, in order to compare objectively different hazard conditions and to minimize references to qualitative hazard attributes such as activity states. The idea of multi-temporal analysis set forth by Cardinali et al. (Nat Hazards Earth Syst Sci 2:57–72, 2002), has been stressed here to compute average recurrence time for individual landslides and to forecast their behaviour within reference time periods. The method is based on the observation of the landslide activity through aerial-photo surveys carried out in several time steps. The output is given by a landslide hazard map showing the mean return period of landslides reactivation. Assessing the hazard in a quantitative way allows for estimating quantitatively the risk as well; thus, the probability of the exposed elements (such as people and real estates) to suffer damages due to the occurrence of landslides can be calculated. The methodology here presented is illustrated with reference to a sample area in Central Italy (Umbria region), for which both the landslide hazard and risk for the human life are analysed and computed. Results show the powerful quantitative approach for assessing the exposure of human activities to the landslide threat for a best choice of the countermeasures needed to mitigate the risk.An erratum to this article can be found at     

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...     

西藏贡觉县泥石流灾害研究

西藏自治区贡觉县境内对居民存在影响的泥石流沟有3条，即者龙洼Ⅰ沟，者龙洼Ⅱ沟，克西林沟，均位于该县东南部的高山峡谷区。泥石流沟长度均超过2km，沟床平均纵坡降130‰，地表松散物质的厚度都在6．5m以上，其来源有所不同，克西林沟泥石流的固体物质来源于沟谷两侧的也古、拉巴滑坡堆积物；者龙洼Ⅰ、Ⅱ泥石流的固体物质来源主要为岩石风化物质及崩、坡积物。固体物质颗粒粒径分布范围很广，分布曲线均呈三峰型。说明该区泥石流中固体物质含量较高。贡觉县境内泥石流的诱发因素是降雨，为降雨型泥石流。文章根据非饱和土强度理论对贡觉县降雨型泥石流的成因机理进行了研究，提出降雨型泥石流的形成过程可以划分为2个阶段，第1个阶段为基质吸力引起的抗剪强度丧失阶段，与前期实效降雨量有关；第2个阶段为泥石流发生阶段，与短历时强降雨有关。运用上述理论方法，对降雨型泥石流的预测模型进行了探讨。建议用临界雨量线模型框架来建立贡觉县泥石流的预测模型，并依据者龙洼Ⅱ沟泥石流爆发前20d的降雨量数据进行拟合分析，结果表明：文中建议的2个临界雨量线模型框架均适于用建立贡觉县降雨型泥石流暴发的预报模型。     

Flood hazard and risk assessment in Russia

Flood risk assessment is usually performed by application of sophisticated mathematical models of river flow. However, there are cases when it is required to assess the risk in the lack of data conditions or a limited time available. In such cases, it is advisable to use some simplifications, which provide reliable results faster. This study proposes a hybrid approach to the flood risk assessment combining quantitative and qualitative indicators. The article describes various methods to assess the flood risk, such as likelihood of flooding, magnitude of the flood, average annual damage, maximum damage and expectation of damage. The authors examined special cases of calculation of the mathematical expectation of harm and zoning in the corresponding indicators. This approach is designed for the conditions of the Russian Federation, but it can be adapted for other regions. It is based on the use of two types of risk maps. The first type of maps is intended to define the mathematical expectation of damage zones for reference building with possibility of risk calculation for other buildings using multiple factors. The second type of maps is designed for the purposes of land use regulation for floodplains based on a priori statistical estimates of flood risk.     

Flood hazard and risk assessment in Russia

The occurrence of rockfall incidents on the transportation network may cause injuries, and even casualties, as well as severe damage to infrastructure such as dwellings, railways, road corridors, etc. Passive protective measures (i.e., rockfall barriers, wire nets, etc.) are mainly deployed by operators of ground transport networks to minimize the impact of detrimental effects on these networks. In conjunction with these passive measures, active rockfall monitoring should ideally include the magnitude of each rockfall, its initial and final position, and the triggering mechanism that might have caused its detachment from the slope. In this work, the operational principle of a low-cost rockfall monitoring and alerting system is being presented. The system integrates measurements from a multi-channel seismograph and commercial cameras as the primary equipment for event detection. A series of algorithms analyze these measurements independently in order to reduce alarms originated by surrounding noise and sources other than rockfall events. The detection methodology employs two different sets of algorithms: Time–frequency analyses of the rockfall event’s seismic signature are performed using moving window pattern recognition algorithms, whereas image processing techniques are utilized to deliver object detection and localization. Training and validation of the proposed approach was performed through field tests that involved manually induced rockfall events and recording of sources (i.e., passing car, walking people) that may cause a false alarm. These validation tests revealed that the seismic monitoring algorithms produce a 4.17 % false alarm rate with an accuracy of 93 %. Finally, the results of a 34-day operational monitoring period are presented and the ability of the imaging system to identify and exclude false alarms is discussed. The entire processing cycle is 10–15 s. Thus, it can be considered as a near real-time system for early warning of rockfall events.     

区域滑坡灾害预测预警与风险评价

区域滑坡灾害预测预警是滑坡灾害研究领域的难点和热点。过去10多年来在这方面的研究主要集中在区域降雨与地质环境的结合方面。文章总结了目前国内外滑坡灾害预测预报、预警和风险管理研究现状,认为把滑坡灾害预警预报与风险管理相结合是减灾防灾的需要,也是今后该领域研究的发展趋势。文章从区域滑坡灾害空间预测、时间预警预报的角度提出了滑坡灾害预测预报的分类和理论基础,并在此基础上,利用MapGIS软件平台进行二次开发,建立了基于WebGIS的滑坡灾害信息管理系统和实时预警发布系统。以2004年"云娜"台风期间浙江省永嘉县滑坡灾害预警预报为例,进行了滑坡危险性预测、人口易损性预测、经济易损性预测到风险预测的实例研究。     

Hazard assessment model for debris flow prediction

Debris flow disasters have plagued Taiwan in recent decades, and caused casualties and destruction of property. Several methods, including the numerical method, statistical method, and experimental method, have been adopted in recent years to predict debris flow, and more recently, the neural network (NN) and the genetic algorithm (GA) methods have been introduced to simulate the occurrence of debris flows. This study proposes using the GA to weigh seven important variables according to principles similar to natural selection. The study then simultaneously inputs these variables into a NN model to predict debris flow occurrences based on relevant factors. There were 154 potential cases of debris flow collected from eastern Taiwan and fed into the model for testing. The average ratio of successful prediction reached 94.94%, which demonstrates that the proposed model can provide stable and reliable results for predicting debris flow in hazard mitigation and guard systems.