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.     

Analysing post-earthquake landslide susceptibility using multi-temporal landslide inventories——a case study in Miansi Town of China

The earthquake that occurred on May 12, 2008, in Wenchuan County aroused a great deal of research on co-seismic landslide susceptibility assessment, but there is still a lack of an evaluation method that considers the activity state of the landslide itself. Therefore, this paper establishes a new susceptibility evaluation model that superimposes the active landslide state based on previous susceptibility evaluation models. Based on a multi-phase landslide database, the probabilistic approach was used to evaluate landslide susceptibility in the Miansi town over many years. We chose the elevation, slope, aspect, and distance from the channel as trigger factors and then used the probability comprehensive discrimination method to calculate the probability of landslide occurrence. Then, the susceptibility results of each period were calculated by superposition with the activity rate. The results show that between 2008 and 2014, the proportion of areas with low landslide susceptibility in the study area was the largest, and the proportionof areas with the highest susceptibility was minimal. The landslide area with highest susceptibility gradually decreased from 2014 to 2017. However, in 2017, 15.06% of the area was still with high susceptibility, and relevant disaster prevention and reduction measures should be taken in these areas. The larger area under the receiver operating characteristic curve(AUC) indicates that the results of the landslide susceptibility assessment in this study are more objective and reliable than those of previous models. The difference in the AUC values over many years shows that the accuracy of the evaluation results of this model is not constant, and a greater number of landslides or higher landslide activity corresponds to a higher accuracy of the evaluation results.     

Optimizing the frequency ratio method for landslide susceptibility assessment: A case study of the Caiyuan Basin in the southeast mountainous area of China

Bivariate statistical analysis of data-driven approaches is widely used for landslide susceptibility assessment, and the frequency ratio(FR) method is one of the most popular. However, the results of such assessments are dominated by the number of classes and bounds of landslide-related causative factors, and the optimal assessment is unknown. This paper optimizes the frequency ratio method as an example of bivariate statistical analysis for landslide susceptibility mapping based on a case study of the Caiyuan Basin, a region with frequent landslides, which is located in the southeast coastal mountainous area of China. A landslide inventory map containing a total of 1425 landslides(polygons) was produced, in which 70% of the landslides were selected for training purposes, and the remaining were used for validationpurposes. All datasets were resampled to the same 5 m × 5 m/pixel resolution. The receiver operating characteristic(ROC) curves of the susceptibility maps were obtained based on different combinations of dominating parameters, and the maximum value of the areas under the ROC curves(AUCs) as well as the corresponding optimal parameter was identified with an automatic searching algorithm. The results showed that the landslide susceptibility maps obtained using optimal parameters displayed a significant increase in the prediction AUC compared with those values obtained using stochastic parameters. The results also showed that one parameter named bin width has a dominant influence on the optimum. In practice, this paper is expected to benefit the assessment of landslide susceptibility by providing an easy-to-use tool. The proposed automatic approach provides a way to optimize the frequency ratio method or other bivariate statistical methods, which can furtherfacilitate comparisons and choices between different methods for landslide susceptibility assessment.     

采用多模型融合方法评价滑坡灾害易发性:以湖北省五峰县为例

不同的易发性评价模型可以得到有差异的滑坡空间预测结果，选取最优模型甚至综合各模型的优势是提高易发性评价精度的有效方法。为检验模型融合思路的有效性，以鄂西地区五峰县渔洋关镇为研究区，提取坡度、地层、断层、河流、公路等7个滑坡成因条件，分别采用信息量模型、证据权模型和频率比模型进行滑坡易发性评价；并将3种模型分别进行归一化、主成分分析（PCA，Principal component analysis）和优势融合，得到了6幅易发性分区图。结果表明:优势耦合模型精度最高（90.3%），频率比模型次之（89.7%），归一化融合模型和PCA融合模型分别为89.3%和89.1%，以上4种结果的精度均高于证据权模型（87.7%）和信息量模型（87.6%）；6幅预测图对应的评价结论与历史滑坡空间分布的实际情况相符。空间一致性对比结论表明，主成分融合模型与优势耦合模型的同格率高达68%，其预测结果避免了单个模型预测结论带来的偶然性和片面性，说明多模型融合方法与优势耦合模型在提高滑坡易发性预测精度上是可行性的，该思路对其他地区滑坡灾害易发性评价具有借鉴意义。      

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.     

浙江省玄武岩台地稳定性评价:以嵊州市地雅园滑坡为例

玄武岩台地型滑坡是一种特殊的滑坡类型，此前对其稳定性的研究较少。以嵊州市地雅园滑坡为研究对象，采用三维数值模拟的方法进行了稳定性分析评价，首先基于详细的地质资料采用三维模拟软件进行了建模；然后基于P-Ⅲ型分布曲线确定了降雨重现期，分别采用岩土软件MIDAS进行了滑坡稳定性模拟与三维运动模拟平台DAN3D软件进行了滑坡影响范围计算；最后对影响地雅园滑坡稳定性的因子进行了敏感性分析。结果表明:不同降雨强度对地雅园滑坡稳定性的影响不同，最不利工况为百年一遇降雨工况，此时滑坡稳定性系数为0.946，破坏概率为65.25%，影响范围最大增加了36.83%；内摩擦角和降雨是影响地雅园滑坡稳定性的主要因子。分析原因认为玄武岩台地型滑坡稳定性主要与硅藻土滑带、节理裂隙面的发育情况、降雨入渗滞后性有明显的相关性。本研究成果可为同类滑坡稳定性评价提供参考依据。      

KARST ENVIRONMENT AND ECO-POVERTY IN SOUTHWESTERN CHINA： A CASE STUDY OF GUIZHOU PROVINCE

1INTRODUCTIONIn the 1980s and 1990s, there was widespread belief a-mong environmentalists that uncontrolled population growth would be responsible for environment degrada-tion of all types. This neo-Malthusian belief originally surfaced in the publication of ThePopulationBombin the late 1960s. In ensuing years this belief, combined with work on environment carrying capacity and a growing environmental movement, led to the seeming-ly commonsense conclusion that high population growth and …     

Regional scale rainfall- and earthquake-triggered landslide susceptibility assessment in Wudu County, China

Wudu County in northwestern China frequently experiences large-scale landslide events.High-magnitude earthquakes and heavy rainfall events are the major triggering factors in the region.The aim of this research is to compare and combine landslide susceptibility assessments of rainfalltriggered and earthquake-triggered landslide events in the study area using Geographical Information System(GIS) and a logistic regression model.Two separate susceptibility maps were produced using inventories reflecting single landslide-triggering events,i.e.,earthquakes and heavy rain storms.Two groups of landslides were utilized: one group containing all landslides triggered by extreme rainfall events between 1995 and 2003 and the other group containing slope failures caused by the 2008 Wenchuan earthquake.Subsequently,the individual maps were combined to illustrate the locations of maximum landslide probability.The use of the resulting three landslide susceptibility maps for landslide forecasting,spatial planning and for developing emergency response actions are discussed.The combined susceptibility map illustrates the total landslide susceptibility in the study area.     

Numerical modeling of bed deposition in rapid flow-like landslides: a case study of the Gaolou landslide in Shaanxi Province,China

Some flow-like landslides tend to lose materials while moving on a relatively dry sliding surface.This phenomenon is called bed deposition.In contrast to the bed entrainment phenomenon,bed deposition is relatively poorly understood.Therefore,an improved depth-averaged model is proposed to quantify this phenomenon.The deposition depth is calculated according to the momentum conservation of the deposited mass,and the rheological property of the sliding mass on the bottom is modified considering an abrupt increase in the depth of the sliding surface after deposition.Utilizing the proposed model,the Gaolou landslide,a typical flowlike landside occurring on October 6 th,2006 with an obvious bed deposition phenomenon in Shaanxi Province of China,is simulated to investigate the influence of bed deposition on its propagation process.The results indicate that the proposed model can effectively depict the bed deposition phenomenon in the Gaolou landslide.Bed deposition dissipates part of the kinetic energy of this landslide;thus,the simulated debris inundation area would likely be overestimated when this effect is neglected.On the other hand,the thin liquefied layer formed by the bed deposition process reduces the friction energy dissipation,contributing to the high mobility of this landslide.     

Evaluation of deep learning algorithms for landslide susceptibility mapping in an alpine-gorge area: a case study in Jiuzhaigou County

With its high mountains, deep valleys, and complex geological formations, the Jiuzhaigou County has the typical characteristics of a disaster-prone mountainous region in southwestern China. On August 8, 2017, a strong Ms 7.0 earthquake occurred in this region, causing some of the mountains in the area to become loose and cracked. Therefore, a survey and evaluation of landslides in this area can help to reveal hazards and take effective measures for subsequent disaster management. However, differ...     

确定性系数与随机森林模型在云南芒市滑坡易发性评价中的应用

编制科学的滑坡易发性分区图,可以有效降低灾害带来的损失。以云南省芒市为研究区,利用确定性系数模型（certainty factor,简称CF）方法计算各个因子的敏感值,作为随机森林（random forests,简称RF）的分类数据,选取合适的训练数据和最优化的模型参数进行模型预测,从而对研究区进行滑坡易发性评价分区。采用频率比方法将连续性因子离散化,从而通过确定性系数计算因子不同区间的滑坡易发性,同时利用CF先验模型,对研究区负样本进行选取。通过计算袋外误差得到最优化的RF参数,随后利用RF模型对研究区模型进行训练及预测。绘制ROC曲线和三维遥感影像对预测模型结果分别进行定量和定性评价,结果表明,所得到的模型精度为91%,优于随机抽样得到的结果。最后,采用平均基尼不纯度减少和平均准确度下降两种计算方法计算、评价了研究区各个因子的重要性。基于以上对研究区进行的滑坡易发性评价结果,可以为该区灾害风险评估和管理提供依据。      

An easy approach to assess the susceptibility of a landslide by utilizing simple raster overlay methods: A case study on Huangtupo landslide (P.R. China)

Semi qualitative index based methods using rankings and ratings are commonly used in susceptibility estimations over a wide area. However, generalized ranking and ratings are not applicable for one single landslide. This paper gives an easy and transferable approach to a susceptibility assessment of Huangtupo landslide (P.R. China), using raster addition without taking account for ranking and ratings. Slope, aspect, curvature, location and drainage buffer distance raster data sets have been obtained out of open source digital elevation models using ESRI’s ArcGIS. These conditioning factor raster data sets have been translated into raster data sets including simple yes or no criteria, referring to triggering or not. Subsequently they have been added by raster math to acquire a simple raster overlay map. After that this map is compared to initial displacement measurements, obtained by using a ground based synthetic aperture radar device. Acquired data is recalculated to a raster data set using the same spatial extent, to provide the possibility of comparison of the two raster data sets. The results reveal, that 76.35% of all measured movements occur in areas where raster cells include three or more conditioning factors, indicating that easy raster math operations can lead to satisfying results in local scale.     

Hollow villages and rural restructuring in major rural regions of China: A case study of Yucheng City, Shandong Province

The agricultural land resources of China are relatively limited because of its large population.Therefore,balancing the land use for industrialization,urbanization,and food security is a big challenge.In recent years,rural hollowing in China has resulted in numerous of abandoned rural houses,and the areas with abandoned houses need to be restored into agricultural land with effective land consolidation techniques.This study used the method of benefit-cost analysis and the data collected through field surveys conducted in Yucheng City in the northwest of Shandong Province in March 2009,to examine how hollow villages (HVs) to be created and how to solve the problem.The qualitative and quantitative analyses indicate following results.1) The situation of HVs is becoming increasingly severe under rapid industrialization and urbanization in Yucheng City.2) Poor infrastructure in rural areas and incomplete urbanization are the main factors that have led to the rural hollowing in many major rural regions of China.3) In order to resolve the problem caused by HVs and increase agricultural land,reconstructing rural communities in the countryside is necessary.4) A new mechanism in the provision of compensation funds by developed regions to the villages in less-developed regions must be established.     

Application of multi-agent models to urban expansion in medium and small cities: A case study in Fuyang City, Zhejiang Province, China

In this study, three-phase satellite images were used to define rules for the allocation of time and space in construction land resources based on a complex adaptive system and game theory. The decision behavior and rules of government agent, enterprise agent and resident agent in construction land growth were explored. A distinctive and dynamic simulation model of construction land growth was built, which integrated multi-agent, GIS technology and RS data and described the interaction among influencing agents, Taking Fuyang City in the Changjiang River Delta as an example, an assessment process for the remote sensing data in construction land and scenario planning was constructed. Repast and ArcGIS were used as simulation platforms. A simulation of the spatial pattern in land-use planning and the setting of scenario planning were conducted by using the incomplete active game, which was based on different natural, social and economic levels. Through this model, a simulation of urban planning space and decision-making for Fuyang City was created. Relevant non-structured problems arising from urban planning management could be identified, and the process and logic of urban planning spatial decision-making could thus be improved. Cell-by-cell comparison showed that the simulation accuracy was over 72%. This model has great potential for use by government and town planners in decision support and technique support in the policy-making process.     

Risk-based evaluation on geological environment carrying capacity of mountain city - A case study in Suide County,Shaanxi Province,China

With the rapid development and expansion of the cities in China, the carrying capacity of resource and environment has become a huge concern for local governments. From the perspective of geological environment, geological disasters are the main restraining factor of the development in mountain cities. This study was conducted in Suide County of Shaanxi Province with a risk-based approach as followed: a hazard analysis on geological disasters based on a slope geological survey at a scale of 1:10,000; a consequence analysis based on unmanned aerial vehicle (UAV) aerial survey data; integrating the results of hazard analysis and consequence analysis, a risk zonation and analysis of geological disasters in urban areas were completed considering urban planning, land use planning and the safety of infrastructure and major engineering. Subsequently, taking the acceptable levels of human life and property risks incurred by landslides as the criteria of the evaluation of geological environment carrying capacity, a comprehensive assessment of current and future urban carrying capacity was conducted based on the results of the risk analyses. Accordingly, the prior development zone, the restricted development zone and the prohibited zone were delineated, with corresponding suggestions for future urban development. The technological and methodological system used in the study can be applied to geological environment carrying capacity evaluation of other important mountain cities, which can provide scientific basis for the optimization of land and space.     

INDUSTRIAL LINKAGES AND RURAL INDUSTRIALIZATION: A CASE STUDY OF HENAN PROVINCE, CHINA

The fast growth of rural industry in China has generated regional development of large rural areas. What role does industrial linkages play in Chinese rural industrialization? This is a same question as the relation between industrial linkages and regional development which has been discussed for decades and no final conclusion reached. The paper pursues the discussion and focuses on rural areas in China with special reference to Henan Province. On the basis of data from an investigation on nearly 200 industrial enterprises, this study emphasizes that the linkages play a very important role in spreading development of industry in rural areas. It is recommended that the national policies should prompt industrial linkages to upgrade the technological level of rural industry and to integrate rural industry with urban industry.     

Pattern dynamics of thermal-environment effect during urbanization: A case study in Shenzhen City, China

The thermal-environment effect exists in the field of rapid urbanization.It has adverse effects on the urban atmosphere,regional climate,energy consumption,and public health.Shenzhen,a representative of rapidly urbanizing cities in China,was selected as a case for pattern dynamics analysis of the thermal environment.The surface temperature was acquired from the thermal infrared data of Landsat TM and ETM+ images in 1986,1995,and 2005 by Jiménez-Mu?oz and Sobrino’s generalized single-channel method,which was used in assessing the distribution and spatial patterns of the thermal environment.The relative thermal environment curve(RTC) was combined with Moran’s I analysis to assess the pattern dynamics of the thermal environment in different urbanization periods.Moran’s I index and the RTC represent a process of aggregation-fragmentation-aggregation,which shows the aggregation pattern of a decrease during the rapid urbanization period and then an increase during the steady urbanization period.High-temperature areas gradually expanded to a uniform and scattered distribution in the rapid urbanization period;while the high thermal-environment effect was gradually transformed into a steady spatial pattern in the stable urbanization period.To characterize the increasing development in this multiple-center city,we chose profiles along an urban-development axis.The results suggest that heat islands have expanded from internal urban to external urban areas.Four profiles were obtained showing differences in shape due to spatial differences in the process of development.     

Characteristics and mechanism of agricultural transformation in typical rural areas of eastern China: A case study of Yucheng City,Shandong Province

Rural off-farm employment, rapid loss of agricultural land, and advanced technology popularization had led agricultural production in Chinese typical rural areas come at a critical transformation and upgrade stage. Based on sample survey data gathered from 401 households in Yucheng City, Shandong Province, this paper focuses on the characteristics and mechanism of agricultural transformation in typical rural areas of the eastern China. It was found that 74.3% of households surveyed kept at least one member engaging in off-farm employment, and 57.1% looked forward to expanding the operational scale of arable land, while just 13.7% had actually transferred their agricultural land. Since growing off-farm employment does not result in the collapse of traditional subsistence agriculture, therefore, agricultural production in Yucheng City is at an incomplete transformation phase from traditional small-holder farming to modern scale economy. It is caused by both macro environments and family characteristics, while urban-rural dual structure, imperfect rural development policy and agricultural technology popularization make peasant economy strengthen upon maintenance, and small-holder farming becomes peasant’s natural response owing to pluriactivity, local off-farm employment, reverse elimination, etc. In order to achieve smooth agricultural transformation of typical rural areas in the eastern China, it needs to promote professional differentiation among peasants, under clear policies adopted by central government. Providing comprehensive services for agricultural production and improving production skills and knowledge of farmers who are still living in the countryside will effectively stimulate the process of agricultural transformation.     

Design of an index system for deep groundwater management efficiency evaluation: A case study in Tianjin City,China

An effective evaluation system can provide specific and practical suggestions to the deep groundwater management. But such kind of evaluation system has not been proposed in China. In this study, an evaluation index system is specifically developed to evaluate deep groundwater management efficiency. It is composed of three first-level indicators (law enforcement capability, management ability, and management effectiveness) and eleven second-level indicators. The second-level indicators include seven mandatory indicators and four optional indicators. Piecewise linear function is used to normalize the quantitative indicators, and expert scoring method and questionnaire survey method are used to normalize the qualitative indicators. Then a comprehensive indicator weighting evaluation method is used to evaluate the first-level indicators and the target topic. A case study is carried out to evaluate deep groundwater management efficiency in Tianjin City. According to the evaluation score in each period, the management efficiency of every district in Tianjin City gradually improved. The overall evaluation score in the early deep groundwater extraction period is 0.12. After a series of deep groundwater protection efforts, this score reached to 0.61 in 2007, and met the regulation criteria. The evaluation results also showed that the further groundwater management efforts in Tianjin City should be focused on building a dynamic database to collect comprehensive deep well-log data; and on a reasonable design and distribution of the groundwater monitoring network. It demonstrated that the index system is suitable to locate the deficiencies of current groundwater management systems and to guide further improvements. It can then be used to protect deep groundwater.     

Administrative urbanization and city-making in post-reform China: a case study of Ordos City,Inner Mongolia

In post-reform China, local governments, instead of the central state, have become major promoters of urbanization. Differing from the existing literature based on Western theories, this article argues that a localized perspective, ‘administrative urbanization', can provide a contextual explanation for the mechanism of urbanization in the reform era. The case study of Ordos indicates that new town construction, especially in the inland area, has become the main strategy for investment attraction and economic development. The local government has played a dominant role in this construction through a series of administrative measures, including avoidance of central state regulations, land leasing, high standard infrastructure construction, relocation policies and industrial attraction. This article also explores the issue of unsustainability in the new town, and identifies that underdeveloped industrialization, slow population agglomeration and real estate bubbles are primary threats to the sustainability of administrative urbanization.