"莫拉克"台风引起的滑坡泥石流灾害HJ-1图像遥感监测研究

利用HJ-1星2009年"莫拉克"台风前后获取的2个时相图像,通过去相关拉伸 (Decorrelation Stretch)、光谱信息增强和最大似然法分类提取滑坡、泥石流区域,并结合TRMM (Tropical Rainfall Measuring Mission)卫星降雨量数据和DEM (Digital Elevat...     

Risk degree of debris flow applying neural networks

A number of methods for prediction of debris flows have been studied. However, the successful prediction ratios of debris flows cannot always maintain a stable and reliable level. The objective of this study is to present a stable and reliable analytical model for risk degree predictions of debris flows. This study proposes an Artificial Neural Networks (ANN) model that was constructed by seven significant factors using back-propagation (BP) algorithm. These seven factors include (1) length of creek, (2) average slope, (3) effective watershed area, (4) shape coefficient, (5) median size of soil grain, (6) effective cumulative rainfall, and (7) effective rainfall intensity. A total of 171 potential cases of debris flows collected in eastern Taiwan were fed into the ANN model for training and testing. The average ratio of successful prediction reaching 99.12% demonstrates that the presented ANN model with seven significant factors can provide a highly stable and reliable result for the prediction of debris flows in hazard mitigation and guarding systems.     

基于流域尺度角半沟泥石流危险性评价

德昌县角半沟流域面积大、地形复杂多样、降雨充沛、物源丰富,具备暴发泥石流的潜在条件。本文通过分析角半沟泥石流的孕灾环境和形成条件,以地形地貌和地质条件为基础,对泥石流流域进行多尺度评价单元划分,采用地形因子、地质因子、水文因子等多因子耦合计算方法,对角半沟泥石流的危险性进行定量评价。利用水文分析方法将角半沟流域45.71km2范围细分为28个评价单元,其中8个处于沟谷发育壮年初期、13个处于沟谷发育壮年中期、5个处于沟谷发育壮年末期、两个处于沟谷发育老年期,运用沟谷型泥石流判定模型计算出角半沟泥石流定量化的危险性评价结果,准确地划分出角半沟泥石流的8处高危险区、6处中危险区、10处低危险区和4处安全区。评价结果能较好反映角半沟泥石流灾害的危险情况,对该地区减灾防灾有重要的指导意义。     

A Debris-flow Simulation Model for the Evaluation of Protection Structures

Debris flow is the flow of a solid-fluid mixture and in this investigation it is treated as the flow of a continuum in routing. A numerical model is proposed describing debris flow including erosion and deposition processes with suitable boundary con-ditions. The numerical model is applied to evaluate the effects of protection structures against debris flow caused by heavy rainfall on the Shen-Mu Stream of Nantou County located in central Taiwan. Simulation results indicated that the proposed model can offer useful pre-planning guidelines for engineers.     

A procedure for making objective preliminary assessments of outburst flood hazard from moraine-dammed lakes in southwestern British Columbia

Existing methods of evaluating the hazard posed by moraine-dammed lakes are unsystematic, subjective, and depend on the expertise and biases of the geoscientist. In this paper, we provide a framework for making objective preliminary assessments of outburst flood hazard in southwestern British Columbia. Our procedure relies on remote sensing methods and requires only limited knowledge of glacial processes so that evaluations of outburst flood hazard can be incorporated into routine hazard assessments of glaciated regions. We describe objective approaches, which incorporate existing empirical relations applicable to the study region, for estimating outburst peak discharge, maximum volume, maximum travel distance, maximum area of inundation, and probability. Outburst flood hazard is greatest for moderately large lakes that are impounded by large, narrow, ice-free moraine dams composed of sedimentary rock debris and drain into steep, sediment-filled gullies above major river valleys. We demonstrate the application of the procedure using three case studies and show that flood hazard varies, especially with major changes in lake level. Our assessment scheme yields reproducible results and enables engineers and geoscientists to prioritize potentially hazardous lakes for more detailed field investigation.     

北京密云县泥石流沟危险性的云模型评价

为了解决泥石流危险性评价过程中定性与定量相互转换的问题, 本文基于云模型理论建立了泥石流危险性评价的模型。首先根据泥石危险性的10个评价因子等级的分类标准获得各因子每个等级的数字特征, 将实测泥石流沟各项指标的数据利用正向云发生器进行整合计算, 得出各沟在各危险级别所对应的确定度。将评价因子的权重代入, 计算出泥石流沟在对应各个等级的综合确定度, 因此来确定泥石流沟的危险性等级。本文通过实测北京市密云县4条泥石流沟的实测值进行了云模型的危险性评价, 将云模型评价结果与可拓学评价结果进行了对比分析, 发现两者的评价结果基本一致, 认为云模型对泥石流危险性评价结果能够较准确地反映出泥石流的危险性水平, 其评价结果具有一定的合理性和可靠性。     

Mutual Interference of Two Debris Flow Deposits Delivered in a Downstream River Reach

We investigate experimentally the depositions of two contiguous debris flows flowing into a main river reach.The aim of the present experimental research is to analyze the geometry and the mutual interactions of debris flow deposits conveyed by these tributaries in the main channel.A set of 19 experiments has been conducted considering three values of the confluence angle,two slopes of the tributary,and three different triggering conditions（debris flows occurring simultaneously in the tributaries,or occurring first either in the upstream or in the downstream tributary）.The flow rate along the main channel was always kept constant.During each experiment the two tributaries had the same slope and confluence angle.The analysis of the data collected during the experimental tests indicates that the volume of the debris fan is mainly controlled by the slope angle,as expected,while the shape of the debris deposit is strongly influenced by the confluence angle.Moreover,in the case of multiple debris flows,the deposit shape is sensitive to the triggering conditions.Critical index for damming formation available in literature has been considered and applied to the present case,and,on the basis of the collected data,considerations about possible extension of such indexes to the case of multiple confluences are finally proposed.     

ESTIMATIONS OF THE SHAPE AND VOLUME OF A STONY DEBRIS FLOW FAN

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Numerical simulation on a tremendous debris flow caused by Typhoon Morakot in the Jiaopu Stream,Taiwan

In August 2009,Typhoon Morakot brought a large amount of rainfall with both high intensity and long duration to a vast area of Taiwan.Unfortunately,this resulted in a catastrophic landslide in Hsiaolin Village,Taiwan.Meanwhile,large amounts of landslides were formed in the Jiaopu Stream watershed near the southeast part of the Hsiaolin Village.The Hsiaolin Village access road（Provincial Highway No.21 and Bridge No.8） was completely destroyed by the landslide and consequent debris flow.The major scope of this study is to apply a debris flow model to simulate the disaster caused by the debris flow that occurred in the Jiaopu Stream during Typhoon Morakot.According to the interviews with local residents,this study applied the destruction time of Bridge No.8 and Chen＇s house to verify the numerical debris flow model.By the spatial rainfall distributions information,the numerical simulations of the debris flow are conducted in two stages.In the first stage（before the landslide-dam failure）,the elevation of the debris flow and the corresponding potential damages toward residential properties were investigated.In the second stage（after the landslidedam failure）,comparisons of simulation results between the longitudinal and cross profiles of the Jiaopu Stream were performed using topographic maps and satellite imagery.In summary,applications of the adopted numerical debris flow model have shown positive impact on supporting better understanding of the occurrence and movement of debris flow processes.     

角半沟泥石流灾害风险评价

德昌县角半沟流域降雨充沛、物源丰富,极易暴发山洪泥石流。本文结合角半沟流域的实际气候、水文、地质、资源、人口、经济等条件,选取相应的评价因子对泥石流灾害进行了风险性评价。泥石流危险度、易损度分别为0.644、0.876,属于高度危险、极高度易损泥石流沟; 风险度为0.564,属于高风险泥石流沟,容易暴发规模较大的泥石流灾害。针对角半沟泥石流特征和评价结果,初步提出了监测预警与工程整治（拦挡坝、拦挡网、固床坝等）相结合的综合治理措施,以期为泥石流灾害的减灾防灾工作提供理论支持。