三峡库区万州主城区第四系堆积层厚度的估算方法及应用

堆积层厚度是区域地质灾害体稳定性预测及定量评估不可或缺的基础数据,传统的空间插值方法制图效率低,精度也较差。以三峡库区万州主城区为研究对象,通过分析区内第四系堆积层厚度标志得出各标志因子,根据已知厚度区域的特点提取堆积层厚度与其标志因子之间的关系,建立了基于随机森林算法的堆积层厚度模型,最后将该模型应用于整个区域估算出堆积层厚度的空间分布。特征点的预测值与实测值的比较结果表明:模型整体的误差变异小,预测的准确度较高,预测结果具有较高的可信度。      

Regional landslide hazard assessment based on Distance Evaluation Model

There are many factors influencing landslide occurrence. The key for landslide control is to confirm the regional landslide hazard factors. The Cameron Highlands of Malaysia was selected as the study area. By bivariate statistical analysis method with GIS software the authors analyzed the relationships among landslides and environmental factors such as lithology, geomorphy, elevation, road and land use. Distance Evaluation Model was developed with Landslide Density(LD). And the assessment of landslide hazard of Cameron Highlands was performed. The result shows that the model has higher prediction precision.     

GIS COMPONENT BASED 3D LANDSLIDE HAZARD ASSESSMENT SYSTEM：3DSLOPEGIS

In this paper ,based on a new Geographic Information System(GIS) grid-based three-dimensional (3D) deterministic model and taken the slope unit as the study object ,the landslide hazard is mapped by the index of the 3D safety factor ,Compared with the one-dimensional(1D) model of infinite slope,which is now widely used for deterministic model based landslide hazard assessment in GIS,the GIS grid-based 3D model is more acceptable and is more adapt-able for three-dimensional landslide.Assuming the initial slip as the lower part of an ellipsoid ,the 3D critical slip surface in the 3D slper stability analysis is obtained by means of a minimization of the 3D safety factor using the Monte Carlo random simulation.Using a hydraulic model tool for the watershed analysis in GIS,an automatic process has been devel-oped for identifying the slope unit from digital elevation model(DEM)data,Compared with the grid-based landslide hazard mapping method ,the slope unit possesses clear topograhical meaning,so its results are more credible,All the calcula-tions are implemented by a computational program,3DSlopeGIS,in which a GIS component s used for fulfilling the GIS spatial analysis function.and all the data for the 3D slope safety factor calculation are in the from of GIS data (the vector and the grid layers).Because of all these merits of the GIS-based 3D landslide hazard mapping method,the complex algo-rithms and iteration procedures of the 3D problem can also be perfectly implemented.     

Regional landslide hazard assessment based on Distance Evaluation Model

There are many factors influencing landslide occurrence. The key for landslide control is to confirm the regional landslide hazard factors. The Cameron Highlands of Malaysia was selected as the study area. By bivariate statistical analysis method with GIS software the authors analyzed the relationships among landslides and environmental factors such as lithology, geomorphy, elevation, road and land use. Distance Evaluation Model was developed with Landslide Density （LD）. And the assessment of landslide hazard of Cameron Highlands was performed. The result shows that the model has higher prediction precision.     

基于滑带完整性指标的三峡库区堆积层滑坡失稳破坏判据

滑坡稳定性评价是滑坡防治中关键问题之一,滑坡失稳破坏判据研究可为滑坡稳定性评价提供支持。为了提高滑坡稳定性评价的精度,以滑坡深部位移监测数据为基础的滑坡失稳破坏判据不失为一种有效方法。基于滑坡深部位移监测数据,引入滑带完整性指标,推导得到了滑带完整性指标与滑坡抗剪强度参数之间呈正比例关系;运用滑坡稳定性计算方法和三峡库区堆积层滑坡简化模型,获得了滑带完整性指标与滑坡的稳定性系数之间呈正比例关系。建立了考虑滑带完整性指标的三峡库区堆积层滑坡失稳破坏判据,即：当滑坡滑带土完整性指标大于滑坡滑带土完整性指标的临界值时,滑坡处于稳定状态;当滑坡滑带土完整性指标小于滑坡滑带土完整性指标的临界值时,滑坡发生失稳破坏。以三峡库区典型堆积层滑坡——五尺坝滑坡为例,通过实例分析发现该判据具备可靠性,对堆积层滑坡适用性好。研究成果表明,滑带完整性指标失稳破坏判据可以用于评价滑坡的稳定状态,为滑坡失稳破坏判据研究提供了一种新思路。     

Probabilistic seismic landslide hazard assessment: a case study in Tianshui,Northwest China

Probabilistic analysis in the field of seismic landslide hazard assessment is often based on an estimate of uncertainties of geological, geotechnical,geomorphological and seismological parameters.However, real situations are very complex and thus uncertainties of some parameters such as water content conditions and critical displacement are difficult to describe with accurate mathematical models. In this study, we present a probabilistic methodology based on the probabilistic seismic hazard analysis method and the Newmark's displacement model. The Tianshui seismic zone(105°00′-106°00′ E, 34°20′-34°40′ N) in the northeastern Tibetan Plateau were used as an example. Arias intensity with three standard probabilities of exceedance(63%, 10%, and 2% in 50 years) in accordance with building design provisions were used to compute Newmark displacements by incorporating the effects of topographic amplification.Probable scenarios of water content condition were considered and three water content conditions(dry,wet and saturated) were adopted to simulate the effect of pore-water on slope. The influence of 5 cm and 10 cm critical displacements were investigated in order to analyze the sensitivity of critical displacement to the probabilities of earthquake-induced landslide occurrence. The results show that water content in particular, have a great influence on the distribution of high seismic landslide hazard areas. Generally, the dry coverage analysis represents a lower bound for susceptibility and hazard assessment, and the saturated coverage analysis represents an upper bound to some extent. Moreover, high seismic landslide hazard areas are also influenced by the critical displacements. The slope failure probabilities during future earthquakes with critical displacements of 5 cm can increase by a factor of 1.2 to 2.3 as compared to that of 10 cm. It suggests that more efforts are required in order to obtain reasonable threshold values for slope failure. Considering the probable scenarios of water content condition which is varied with seasons, seismic landslide hazard assessments are carried out for frequent, occasional and rare earthquake occurrences in the Tianshui region, which can provide a valuable reference for landslide hazard management and infrastructure design in mountainous seismic zones.     

三峡库区堆积层滑坡间歇性活动预测:以白水河滑坡为例

三峡库区堆积层滑坡在季节性降雨和库水位周期波动的影响下呈现间歇性活动特征,滑坡活动强度与诱发因素作用强度和时间关系密切。以三峡库区白水河滑坡为例,分析了堆积层滑坡间歇性活动特征和诱发因素,发现降雨和库水位下降是滑坡变形的主要诱发因素。根据滑坡时序曲线特征,将滑坡累积位移分解为趋势项位移和周期项位移,采用多项式拟合的方法来预测趋势项位移,利用长短期记忆神经网络模型来预测周期项位移,并与极限学习机模型、广义回归神经网络模型的预测结果进行了对比分析,发现长短期记忆神经网络模型预测滑坡间歇性活动精度更高。     

Displacement characteristics and prediction of Baishuihe landslide in the Three Gorges Reservoir

In order to reach the designated final water level of 175 m, there were three impoundment stages in the Three Gorges Reservoir, with water levels of 135 m, 156 m and 175 m. Baishuihe landslide in the Reservoir was chosen to analyze its displacement characteristics and displacement variability at the different stages. Based on monitoring data, the landslide displacement was mainly influenced by rainfall and drawdown of the reservoir water level. However, the magnitude of the rise and drawdown of the water level after the reservoir water level reached 175 m did not accelerate landslide displacement. The prediction of landslide displacement for active landslides is very important for landslide risk management. The time series of cumulative displacement was divided into a trend term and a periodic term using the Hodrick-Prescott(HP) filter method. The polynomial model was used to predict the trend term. The extreme learning machine(ELM) and least squares support vector machine(LS-SVM) were chosen to predict theperiodic term. In the prediction model for the periodic term, input variables based on the effects of rainfall and reservoir water level in landslide displacement were selected using grey relational analysis. Based on the results, the prediction precision of ELM is better than that of LS-SVM for predicting landslide displacement. The method for predicting landslide displacement could be applied by relevant authorities in making landslide emergency plans in the future.     

Status of two Coreius species in the Three Gorges Reservoir,China

Dam construction alters natural flow regimes which,in turn,cause significant changes in fish communities during and after impoundment. The construction of the Three Gorges Reservoir,from impoundment of the Changjiang(Yangtze) River,China,may have affected native fish species. Thus,the status of two lotic freshwater fish species,Coreius heterodon and C.guichenoti,were monitored in the Three Gorges Reservoir,including fish abundance,individual composition,growth,condition,and mortality. Data on both species were gathered from upstream,midstream and downstream areas of the reservoir and,where available,from studies published before and after dam construction. Lower abundance,slower growth,a less diversified age structure,poorer fish condition(indicated by hepatosomatic index) and higher mortalities were recorded in sites nearest the dam compared with upstream areas. Furthermore,after final impoundment,individual Coreius species inhabiting the area changed,with young individuals becoming more abundant,while upstream of the reservoir the two Coreius species became smaller at a given age. The results show that the status of the two Coreius species was subject to dramatic changes after impoundment.     

Spatial distribution,sources and ecological risk assessment of heavy metals in Shenjia River watershed of the Three Gorges Reservoir Area

Surface soil/sediment samples were collected from the Water-Level Fluctuation Zone (WLFZ), cultivated land and forest land at 50 different grid points from Shenjia watershed, the Three Gorges Reservoir area in August 2013. The spatial distribution, sources and ecological risk assessment for Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb) and Zinc (Zn) were analyzed in this study. The results showed all tested metals had similar distribution patterns except Ni and Cr, with areas of high concentrations distributed in the southwest (WLFZ and watershed outlet) of the study area. Ni and Cr, which were highly positively correlated and present in high concentrations, were primarily distributed in the south and middle zones of the study area. Lower concentration areas of all metals were uniformly distributed west of the high-elevation zones and forest land. Factor analysis (FA) and factor analysis-multiple linear regression (FA-MLR) showed that the major sources of Cd were fertilizer and traffic sources, which together accounted for 87% of Cd. As, Zn and Cu levels were primarily supplied by industrial and domestic sources, accounting for 76% of As, 75% of Cu and 67% of Zn. Surface soils/sediments of the study watershed contaminated by Cd represent a high ecological risk, whereas other metals represent low ecological risks. The potential ecological risk index (PERI) analysis indicated that it had a low (wide-range) ecological risk and a moderate (small-range) ecological risk primarily distributed in the outlet of the study watershed. Fertilizers and traffic are the primary sources of Cd pollution, which should be more closely controlled for the purposes of water quality and ecological conservation.     

基于空间多尺度分析的滑坡易发性评价——以三峡库区秭归-巴东段为例

以三峡库区秭归-巴东段为例,将地理加权回归(GWR)模型引入到研究区的空间尺度分割方法中,利用粒子群优化(PSO)算法对支持向量机(SVM)模型参数进行优化,构建GWR-PSO-SVM耦合模型,完成研究区滑坡易发性评价,并与传统的PSO-SVM耦合模型结果进行对比。结果表明,在特定类别精度分析、总体预测精度分析和曲线下面积分析中,本文方法评价效果均优于传统方法。     

Effects of seasonal water-level fluctuation on soil pore structure in the Three Gorges Reservoir,China

Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability. The aim of this study was to investigate the response of soil pore structure to seasonal water-level fluctuation in the reservoir, and particularly, the hydrological change of wetting and drying cycles. Soil pore structure was visualized with industrial X-ray computed tomography and digital image analysis techniques. The results showed that soil total porosity(? 100 ?m), total pore number, total throat number, and mean throat surface area increased significantly under wetting and drying cycles. Soil porosity, pore number and throat numberwithin each size class increased in the course of wetting and drying cycles. The coordination number, degree of anisotropy and fractal dimension were indicating an increase. In contrast, the mean shape factor, pore-throat ratio, and Euler-Poincaré number decreased due to wetting and drying cycles. These illustrated that the wetting and drying cycles made soil pore structure become more porous, continuous, heterogeneous and complex. It can thus be deduced that the water-level fluctuation would modify soil porosity, pore size distribution, and pore morphology in the Three Gorges Reservoir, which may have profound implications for soil processes, soil functions, and bank stability.     

Application of an integrated methodology for eutrophication assessment: a case study in the Bohai Sea

An integrated methodology for eutrophication assessment,which integrates both water quality indicators(causative factors) and ecological response indicators(effect factors),is described.It is then applied to rank the eutrophication status of the years 2007 and 2008 in the southwest Bohai Sea.The assessment model identified that north Bohai Bay and west Laizhou Bay were the two areas with the most serious eutrophication problems in the southwest Bohai Sea.In addition,compared to that in the west Laizhou Bay,the eutrophication conditions in the north Bohai Bay was more serious in both years.Eutrophication problems such as harmful algal blooms(HABs) and low dissolved oxygen(DO) events in north Bohai Bay were frequent.The integrated method outmatched the currently used Chinese nutrient index method by definitely identifying areas with the most serious eutrophication problems,while the nutrient index method gave ambiguous results between the two years.Inclusion of both causative factors and effect factors,combining concentration,spatial coverage and frequency of indicators,as well as use of multi-season monitoring datasets in the methodology result in a more accurate,representative and useful assessment.     

Dynamic Assessment on Regional Eco-environmental Quality Using AHP-Statistics Model—-A Case Study of Chaohu Lake Basin

An indicator system closely connected with eco-environment, in which indicator involves in such fields as society, economy, resources, environment and ecology, is first proposed for eco-environmental quality assessment. Then, a hierarchical model with four levels is established by virtue of these indicators and attributes. In the model, weights of indicators and attributes are determined by combining Delphi method with the Analytic Hierarchy Process (AHP) and a statistic method is used to eliminate the influences arising from the differences in dimension and magnitude of indicators. On these grounds, an AHP-statistics model is provided for regional eco-environmental quality assessment. As a case, such AHP-statistics model is utilized in the dynamic analysis of regional eco-environmental assessment in Chaohu Lake basin. Study results show that natural environmental quality in the watershed was in the declining state while social environmental quality was in a markedly improved situation from 1996, and the synthetic eco-environmental quality was gradually and slowly improved under the common influences of both natural and social environmental factors. Example of application testified the capacities of above methodology to evaluate the real and dynamic state of regional eco-environmental quality.     

三峡库区麻柳林滑坡变形特征及演化模拟

在库水位波动和降雨作用的共同影响下，库岸滑坡的变形规律往往更为复杂。以三峡库区麻柳林滑坡为例，基于野外调查、钻探编录、深部位移监测以及数值模拟等手段，分析了库水位波动和降雨作用下滑坡变形特征及演化规律。结果表明:麻柳林滑坡在粉质黏土层和块石层交界处发育一个次级滑带，目前该滑坡主要沿次级滑带运动，导致次级滑动的原因与坡体物质的差异性有关；S_i(S_f)指标分析法揭示滑坡的滑带还未完全破坏，滑坡仍处于蠕变状态；根据三峡水库水位调度规律，将一个完整水文年划分为6个阶段，数值模拟结果表明滑坡在库水位缓慢下降阶段变形速率较小、在快速下降阶段和低水位阶段变形速率持续增大、在快速上升阶段和缓慢上升阶段以及高水位阶段变形速率则保持平稳。其中，降雨的直接影响和降雨导致库水位波动进而对滑坡变形造成的间接影响，使得麻柳林滑坡在低水位阶段的变形显著增加、稳定性最差，应加强该时段内滑坡的监测和预警。      

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Debris flow susceptibility assessment using a probabilistic approach: A case study in the Longchi area,Sichuan province,China

The Longchi area with the city of Dujiangyan, in the Sichuan province of China, is composed of Permian stone and diorites and Triassic sandstones and mudstones intercalated with slates. An abundance of loose co-seismic materials were present on the slopes after the May 12, 2008 Wenchuan earthquake, which in later years served as source material for rainfall-induced debris flows or shallow landslides. A total of 48 debris flows, all triggered by heavy rainfall on 13th August 20l0, are described in this paper. Field investigation, supported by remote sensing image interpretation, was conducted to interpret the co-seismic landslides in the debris flow gullies. Specific characteristics of the study area such as slope, aspect, elevation, channel gradient, lithology, and gully density were selected for the evaluation of debris flow susceptibility. A score was given to all the debris flow gullies based on the probability of debris flow occurrence for the selected factors. In order to get the contribution of the different factors, principal component analyses were applied. A comprehensive score was obtained for the 48 debris flow gullies which enabled us to make a susceptibility map for debris flows with three classes. Twenty-two gullies have a high susceptibility, twenty gullies show a moderate susceptibility and six gullies have a low susceptibility for debris flows.     

EXPLORATION ON METHOD OF AUTO-CLASSIFICATION FOR MAIN GROUND OBJECTS OF THREE GORGES RESERVOIR AREA

1IN TR O DU C TIO N With thedevelopmentof remotesensingtechnolog,y thestudyandapplicatioonftheautomaticclassifitciaon method usingcomputerhad achievedsatisfyi ndgevel- opment. From spectrumstatisticcallassificatitoonthe neural network classificatimoenthod…     

Comparison of the rise of water level in the typical catchments,Three Gorges Reservoir area

Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments (catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with different areas to provide useful information to inform data extension from a gauged-catchment to an ungauged catchment. The results showed that there are seasonal changes in the dominant driving mode of the rise of the water level. The rise of the water level in March is likely mainly driven by the mode of stored-full runoff, and in September or October, it is mainly driven by Horton-flow. The correlation coefficients of all indexes were significant among the three catchments, suggesting that these catchments have similarities and that water level data extension is likely to be completed successfully between the large catchment (III-Catchment) and the small catchment (I-Catchment). It was confirmed that there is good similarity between the 0.6 km2 and 6 km2 catchments, and the data correlation is good between the catchments with the area differences in the Three Gorges Reservoir Area. In addition, the rise processes of the water level in the catchments were not only different under the same rain conditions, but this difference could also change with the rain condition.     

三峡库区典型样带潜热通量遥感反演与验证

本文以三峡库区腹地的部分地区为典型样带,利用遥感数据的时效性和区域性优势,结合常规气象数据,定量反演样带地表潜热通量,并对比验证遥感反演方法的可行性和可靠性。结果表明：潜热通量在不同地表覆被状况下呈现较大差异,城镇居民区和无植被覆盖区一般在20~80W·m^-2;人工林场、山区森林及草灌和山前农作区在180~280W·m^-2;水体则分布在420~470W·m^-2,潜热通量整体呈现出随地表覆被变化而变化的空间异质性。此外,由于库区地表覆被类型多样,并受到山区起伏地形地貌的影响,潜热通量在空间分布上的地形分异特征也较显著。