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Landslide disasters are one of the main risks involved with the operation of long-distance oil and gas pipelines. Because previously established disaster risk models are too subjective, this paper presents a quantitative model for regional risk assessment through an analysis of the patterns of historical landslide disasters along oil and gas pipelines. Using the Guangyuan section of the Lanzhou–Chengdu–Chongqing (LCC) long-distance multiproduct oil pipeline (82 km) in China as a case study, we successively carried out two independent assessments: a susceptibility assessment and a vulnerability assessment. We used an entropy weight method to establish a system for the vulnerability assessment, whereas a Levenberg–Marquardt back propagation (LM-BP) neural network model was used to conduct the susceptibility assessment. The risk assessment was carried out on the basis of two assessments. The first, the system of the vulnerability assessment, considered the pipeline position and the angle between the pipe and the landslide (pipeline laying environmental factors). We also used an interpolation theory to generate the standard sample matrix of the LM-BP neural network. Accordingly, a landslide susceptibility risk zoning map was obtained based on susceptibility and vulnerability assessment. The results show that about 70 % of the slopes were in high-susceptibility areas with a comparatively high landslide possibility and that the southern section of the oil pipeline in the study area was in danger. These results can be used as a guide for preventing and reducing regional hazards, establishing safe routes for both existing and new pipelines, and safely operating pipelines in the Guangyuan area and other segments of the LCC oil pipeline. [ABSTRACT FROM AUTHOR]

Yang, J., 2018. Landslide damage from extreme rainstorm geological accumulation layers within plain river basins. In: Ashraf, M.A. and Chowdhury, A.J.K. (eds.), Coastal Ecosystem Responses to Human and Climatic Changes throughout Asia. To provide the basis of an early warning and detection for landslide disasters and to provide decision support for local governments in disaster prevention and mitigation, this research studied landslide damage assessment from the geological accumulation layer in a plain river basin under conditions of an extreme rainstorm. Based on an analysis of the relationship between landslide geology and rainfall and a damage model of landslides under conditions of extreme rainfall, the landslide damage assessment described in this article used the SINMAP model. The layer of geological accumulation in the Wenchuan–Diexi River section in the upper reaches of the Minjiang River was the study area. Spatial distribution characteristics and the main factors inducing a landslide disaster were studied, and a danger-evaluation model for landslides in that region was established for landslide assessment research and for applying that research. Based on the SINMAP model, the effects of different extreme rainstorm events on the stability of regional slopes were analyzed. The results of a stability evaluation for landslides show that the area has an unstable zone of 4339.8 km2, which accounts for 64.49% of the total area. The unstable area in this evaluation was basically consistent with the distribution of an existing landslide, which shows that the model can adequately evaluate slope stability and landslide potential from the layer of geological accumulation in this area. [ABSTRACT FROM AUTHOR]

Many landslides were triggered by heavy rainfall from 29 June to 1 July 2017 in Ningxiang County, Hunan Province, China. A field investigation into one of the landslides, known as the Wangjiawan landslide, was undertaken on July 3, 2017, to understand the landslide mechanisms and the factors that triggered the event. The landslide is a translational and rotational slide that degraded downslope to an earth flow. It occurred on a steeply dipping mud-rich slate intercalation. Field investigation shows that the landslide had a movement rate of more than 25 m/s and had been triggered by up to 338 mm of continuous rainfall over 2 days. The landslide was fast-moving because it occurred on a steep slope and showed a rapid reduction in shear strength. The landslide resulted in nine fatalities and 19 injuries, most during initial rescue efforts. To mitigate a possible secondary landslide disaster, later emergency measures including evacuation of the survivors, setting up warning signs, and covering landslide cracks with plastic sheeting were adopted. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to establish a data-driven approach and assess its potential for shallow landslide susceptibility mapping of the Shennongjia Forestry District, China. For the data processing, Fisher segmenting was used for the classification of topographical factors (gradient, relief amplitude, plan curvature, and normalized difference vegetation index) and the improved Otsu method was used to determine the buffer length thresholds of the locational factors (proximity to roads, rivers and faults). The computations show that these two objective methods help to avoid the uncertainty caused by the subjective judgments and the obtained thresholds are more consistent with actual conditions. Considering the different data types, the locational and topographical factors were evaluated by fuzzy comprehensive evaluation while the geological factors were evaluated by frequency index, and then the three separate evaluations were combined using radar chart analysis. The validation result shows that the susceptibility map based on a data-driven approach has a high accuracy of prediction and this approach will be salutary for risk mitigation and land-use management in mountainous regions. [ABSTRACT FROM AUTHOR]

The primary objective of the current study is to better understand landslide hazards in reservoir areas and the mechanism of reservoir landslides using different methods. To achieve this main objective the Xiangjiaba Reservoir area, Southwest China is taken as a case study. First, landslide mapping and spatial analysis in the Xiangjiaba Reservoir area were conducted by air photo interpretation (API), followed by field checks. Second, landslide susceptibility mapping was done using the information value method and a logistic regression model. Through remote sensing interpretation coupled with field investigations, 62 landslides, 38 rockfall deposits, and 10 bedrock deformed bodies along the banks of the Xiangjiaba Reservoir area which have effects on the reservoir and resettlements were considered, with a total volume of 32,228 x 104 m³, 19,916 x 104 m³, 1,072 x 104 m³, respectively. Geological characteristics of the reservoir slopes and spatial prediction indicate that after filling the reservoir to a normal level of 380 m, 23 landslides among the total identified landslides are stable, six landslides have been mitigated, and all of the rest are unstable. Thirty-two rockfall deposits are still in a stable state, and the rest are unstable. By overlaying the existing landslide and the susceptibility map, it is found that 0.36% of the existing landslides are in areas of very low susceptibility, 1.77% are in areas of low susceptibility, 4.14% are in areas of moderate susceptibility, 6.04% are in areas of high susceptibility, and 13.37% are in areas of very high susceptibility. [ABSTRACT FROM AUTHOR]

This paper analyzes the typical landslides caused by pipeline construction and the characteristics of landslides during the construction period, and assesses the risk to the long gas and oil pipeline project in China caused by landslides during its construction. Using the semiquantitative risk assessment method and introducing the concept of risk degree, according to the assessment of risk and vulnerability, a landslide disaster risk assessing index system was established after summarizing the causative disaster factors of the landslide disasters induced by the construction of the China-Myanmar pipeline project. Three typical disaster points induced by pipeline construction were chosen to make a risk grade evaluation. The results of site reviews show the evaluation results coincide with the actual situation. Thus, semiquantitative evaluation methods can be used as a reference to guide the landslide disasters developed portion of pipeline construction risk control. [ABSTRACT FROM AUTHOR]

The landslides caused by the 5.12 Wenchuan earthquake resulted in enormous casualties and property losses. Since the earthquake, more than 3,600 landslides have occurred, and 17 of them were catastrophic, each of which has killed more than 30 people. Meanwhile, passive flexible protection has gradually been introduced to resist landslides due to its significant advantages of economy, safety, and environmental protection. To resist landslides effectively, it is necessary to study the load path and design method of passive flexible protection under the action of landslides. In the design of passive flexible protection against landslides, determination of the landslide load is the primary task. In this paper, the formulas of the probability density function and distribution function of the landslide pressure are developed to obtain the value of the accumulated landslide pressure acting on the passive flexible protection, which can be used as the load input parameter in the design of passive flexible protection to resist landslides. Based on the case of the 'Shiziliang' potential landslide for the 5.12 earthquake, the pressure data of the landslide are collected, the calculation formulas of the volume, and the pressure of the intercepted landslide are established, and the statistical parameters of the landslide pressure-loading sample are obtained. According to the Kolmogorov-Smirnov test method, the loading sample of the landslide pressure obeys an extreme-value type-I distribution, and then the load model of the landslide pressure is determined. Based on the reliability analysis method, the standard value of the landslide pressure with an over-95% assurance rate is obtained. These results can provide references for load confirmation to design the passive flexible protection to resist landslides. [ABSTRACT FROM AUTHOR]

The Daguangbao mega-landslide (China), induced by the 2008 Wenchuan earthquake (M w = 7.9), with an area of approximately 8 km 2 , is one of the largest landslides in the world. Experts predicted that the potential risk and instability of the landslide might remain for many decades, or even longer. Monitoring the activity of such a large landslide is hence critical. Terrain Observation by Progressive Scans (TOPS) mode from the Sentinel-1 satellite provides us with up-to-date high-quality Synthetic Aperture Radar (SAR) images over a wide ground coverage (250 × 250 km), enabling full exploitation of various InSAR applications. However, the TOPS mode introduces azimuth-dependent Doppler variations to radar signals, which requires an additional processing step especially for SAR interferometry. Sentinel-1 TOPS data have been widely applied to earthquakes, but the performance of TOPS data-based time series analysis requires further exploitation. In this study, Sentinel-1 TOPS data were employed to investigate landslide post-seismic activities for the first time. To deal with the azimuth-dependent Doppler variations, a processing chain of TOPS time series interferometry approach was developed. Since the Daguangbao landslide is as a result of the collapse of a whole mountain caused by the 2008 Mw 7.9 Wenchuan earthquake, the existing Digital Elevation Models (DEMs, e.g. SRTM and ASTER) exhibit height differences of up to approximately 500 m. Tandem-X images acquired after the earthquake were used to generate a high resolution post-seismic DEM. The high gradient topographic errors of the SRTM DEM (i.e. the differences between the pre-seismic SRTM and the actual post-seismic elevation), together with low coherence in mountainous areas make it difficult to derive a precise DEM using the traditional InSAR processing procedure. A re-flattening iterative method was hence developed to generate a precise TanDEM-X DEM in this study. The volume of the coseismic Daguangbao landslide was estimated to be of 1.189 ± 0.110 × 10 9 m 3 by comparing the postseismic Tandem-X DEM with the preseismic SRTM DEM, which is consistent with the engineering geological survey result. The time-series results from Sentinel-1 show that some sectors of the Daguangbao landslide are still active (and displaying four sliding zones) and exhibiting a maximum displacement rate of 8 cm/year, even eight years after the Wenchuan earthquake. The good performance of TOPS in this time series analysis indicates that up-to-date high-quality TOPS data with spatiotemporal baselines offer significant potential in terms of future InSAR applications. [ABSTRACT FROM AUTHOR]

Fifty-five descending images from the ENVISAT satellite were processed using the small baseline subset (SBAS) method to derive the spatial and temporal ground deformation of the Bailong River Basin between 2003 and 2010. The basin is one of the most severely landslide- and debris flow-affected areas of China. As a result, 104 sites with high deformation areas were identified. Interferometric Synthetic Aperture Radar (InSAR) analysis was combined with landslide inventory data and field surveys, and anomalous areas were classified into three main types: landslide; debris; and subsidence. Displacement rates up to 35 mm/yr were evaluated away from the sensor along a line-of-sight (LOS) direction. The results gained should allow a more accurate prediction and monitoring of landslides, debris, and subsidence; further, they demonstrate the capability of the SBAS method to analyze any displacement effect and identify dangerous and uninhabitable areas in the basin. The small baseline subset method can thus contribute to the prediction and prevention of geohazards in the area. [ABSTRACT FROM AUTHOR]

Landslides are one of the most destructive disasters that cause damage to both property and life every year. The mountainous terrain, heavy and prolonged rainfall and dense development near steep hillsides make Hong Kong as one of the most vulnerable metropolitans to the risk of landslides. Therefore, regional-specific landslide susceptibility assessment in Hong Kong is necessary for hazard management and effective land use planning. Various methodologies have been proposed for landslide susceptibility mappings. By applying the statistically based frequency ratio and logistic regression models in Lantau Island, Hong Kong, this study attempts to add extra value to the literature of evaluating their ‘prediction rate’ (rather than ‘success rate’) for landslide susceptibility mapping in a temporal context. The spatial relationship among landslide occurrence and nine causative factors (elevation, slope, aspect, plan curvature, profile curvature, normalized difference vegetation index (NDVI), distance to river, distance to fault and lithology) were examined, and landslide susceptibility maps were generated by frequency ratio and logistic regression model. Validations of the mapping results were performed by calculating relative operating characteristics (ROC). Virtually all previous studies randomly extracted and reserved a portion of historical landslide records to perform the model evaluation. In contrast, in this study, 1864 (70%) landslide records in the Enhanced Natural Terrain Landslide Inventory from 2000 to 2008 are utilized to train the model, while the subsequent 799 (30%) landslides occurred from 2008 to 2009 are used for model validation. The validation result shows that logistic regression model (84.05%) possesses a better prediction power than frequency ratio model (76.64%) for the study area. This study attempts to offer a new model assessment strategy for landslide susceptibility mapping. The resultant maps also provide a scientific assessment of the risk areas with respect to landslides on Lantau Island and could serve as a basis for decisions or justification of the Lantau development planning. [ABSTRACT FROM PUBLISHER]

Frequent occurrence of landslides in the Chinese Loess Plateau has seriously threatened the urban and rural development. Heifangtai loess platform was selected as a case study for the current research. The platform surface is being largely irrigated since 1968. About 70 landslides of different types have occurred in the region including loess slides, loess flows, combined loess, and bedrock landslides along/across bedding planes. The loess slides occurred in the unsaturated soil and have a shallow failure depth. The loess flows initiated at the contact between loess and underlying clay and can travel a distance of more than 300 m at a speed of up to 5 m/s. Controlled by the topography of the underlying clay layer, the loess flows mainly occurred along the eastern margins of Heifangtai. The combined loess and bedrock landslides along bedding planes typically travel a distance of 30-60 m at a speed of 0.002-0.005 m/s with a volume of up to several million cubic meters. This type of landslide commonly occurred along the southern margins of Heifangtai, where the slope aspects are close to the inclination direction of the bedding planes of underlying bedrocks. Monitoring of perched water table in loess layer at the northern margin of Heifangtai shows the water table is rising at a speed of about 18 cm/year. [ABSTRACT FROM AUTHOR]

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Landslides are occurring more frequently in China under the conditions of extreme rainfall and changing climate, according to News reports. Landslide hazard assessment remains an international focus on disaster prevention and mitigation, and it is an important step for compiling and quantitatively characterizing landslide damages. This paper collected and analyzed the historical landslide events data of the past 60 years in China. Validated by the frequencies and distributions of landslides, nine key factors (lithology, convexity, slope gradient, slope aspect, elevation, soil property, vegetation coverage, flow, and fracture) are selected to construct landslide susceptibility (LS) empirical models by back-propagation artificial neural network method. By integrating landslide empirical models with surface multi-source geospatial and remote sensing data, this paper further performs a large-scale LS assessment throughout China. The resulting landslide hazard assessment map of China clearly illustrates the hot spots of the high landslide potential areas, mostly concentrated in the southwest. The study implements a complete framework of multi-source data collecting, processing, modeling, and synthesizing that fulfills the assessment of LS and provides a theoretical basis and practical guide for predicting and mitigating landslide disasters potentially throughout China. [ABSTRACT FROM AUTHOR]

Hundreds of thousands of landslides were triggered by the May 12, 2008, Mw 7.9 Wenchuan earthquake in China. A detailed inventory of landslides triggered by the earthquake was prepared based on geographic information systems and remote sensing technology. Visual interpretation of high-resolution satellite images and aerial photos taken pre- and post-earthquake and selected field investigation showed that at least 197,481 co-seismic landslides related to the earthquake were triggered throughout an area of approximately 110,000 km 2. These co-seismic landslides are delineated as individual solid polygons. The landslides cover a total area of approximately 1,160 km 2. Most of the landslides are distributed in an approximate ellipse area with a total area of approximately 44,031 km 2. In this paper, quantitative co-seismic landslide criteria for seismic intensity zonation were constructed based on the original “M 8.0 Wenchuan Earthquake Seismic Intensity Map” (MWESIM) and co-seismic landslide abundance analyses. These quantitative criteria, which correspond to landslide area percentages (LAP), indicate the percentage of the area affected by landslides in certain calculation windows and are listed as follows: Areas of LAP ≥70 % correspond to the XII intensity district; areas of 20 % ≤ LAP < 70 % correspond to the XI intensity district; areas of 1 % ≤ LAP < 5 % correspond to the IX intensity district; and areas of LAP <1 % correspond to the VIII and less-than-VIII intensity districts. The VII and greater-than-VII intensity districts of the original MWESIM, which constituted an area of approximately 123,832 km 2, were corrected based on the above quantitative criteria. The degrees of fit of the original and revised MWESIMs with the co-seismic landslides were 93.8 and 95.8 %, respectively, indicating a 2.0 % improvement. The quantitative criteria of the constructed earthquake-triggered landslides for seismic intensity zonation can provide a scientific reference, standard, and basis for seismic intensity zonation in other earthquake events, especially those occurring in mountainous areas. [ABSTRACT FROM AUTHOR]

The authors discuss the landslides triggered by the May 12, 2008 earthquake in Sichuan, China. They also mention the role of slip rate and fault type during the earthquake, debris flow resulting from sediment movement, and conduct of hazard assessment and geological recoinnaissance after the earthquake.

The author reflects on the Wenchuan earthquake in China in on May 12, 2008. Topics discussed include Longmen Shan Mountains which slipped and rocks were deformed, increase risk of landslides in Sichuan Province, compared to pre-quake levels, and destruction of almost one-quarter of the habitat of panda which threatens their ability to feed.