Identification of potential sites of debris flows in the upper Min River drainage,following environmental changes caused by the Wenchuan earthquake

The Wenchuan earthquake caused numerous landslides and collapses that provide abundant unconsolidated material for future mobilization as debris flows.Debris flows will be very active and cause considerable damage for some time in the affected area.Because of environmental changes related to the earthquake,many potentially dangerous debris flow gullies have yet to be identified.This paper selects the upper Min River from Yinxiu to Wenchuan as the study area,interprets the unconsolidated deposits,and discusses their relationship to distance from the fault.Then,applying that information and the values of other factors relating to debris flow occurrence,the locations of potential debris flows are analyzed by multi-factor comprehensive identification and rapid identification.The multi-factor comprehensive identification employs fuzzy matter-element extension theory.The volume of unconsolidated material in the study area is about 3.28 × 108 m3.According to the analysis by multi-factor comprehensive identification,47 gullies have a high probability for potential debris flow,8 gullies have a moderate probability,and 1 gully has a low probability.     

Influences of the Wenchuan Earthquake on sediment supply of debris flows

The 5.12 Wenchuan Earthquake and the subsequent rainstorms induced a large number of landslides, which later were transformed into debris flows. To evaluate the effect of the earthquake on the sediment supply of debris flows, eight debris flow basins near Beichuan City, Sichuan Province, China were chosen as the study area. The area variations of the debris flow source after the Wenchuan Earthquake and the subsequent rainstorm are analyzed and discussed in this paper. Interpretations of aerial photographs (after the 5.12 Wenchuan Earthquake) and SPOT5 images (after the rainstorm event of September 24, 2008) as well as field investigations were compared to identify the transformation of landslide surface in the study area, indicating that the landslide area in the eight debris flow basins significantly increased. The loose sediment area on the channel bed increased after the rainstorm event. In order to estimate the relationship of the landslide area with the rainfall intensity in different return periods, a model proposed by Uchihugi was adopted. Results show that new landslide area induced by heavy rainfall with 50-year and 100-year return period will be 0.87 km2 and 1.67 km2, respectively. The study results show the Wenchuan earthquake had particular influences on subsequent rainfall-induced debris flow occurrence.     

Co-seismic landslide inventory and susceptibility mapping in the 2008 Wenchuan earthquake disaster area, China

The Ms 8.0 May 12,2008 Wenchuan earthquake triggered tens of thousands of landslides.The widespread landslides have caused serious casualties and property losses,and posed a great threat to post-earthquake reconstruction.A spatial database,inventoried 43,842 landslides with a total area of 632 km 2,was developed by interpretation of multi-resolution remote sensing images.The landslides can be classified into three categories:swallow,disrupted slides and falls;deep-seated slides and falls,and rock avalanches.The correlation between landslides distribution and the influencing parameters including distance from co-seismic fault,lithology,slope gradient,elevation,peak ground acceleration(PGA) and distance from drainage were analyzed.The distance from co-seismic fault was the most significant parameter followed by slope gradient and PGA was the least significant one.A logistic regression model combined with bivariate statistical analysis(BSA) was adopted for landslide susceptibility mapping.The study area was classified into five categories of landslide susceptibility:very low,low,medium,high and very high.92.0% of the study area belongs to low and very low categories with corresponding 9.0% of the total inventoried landslides.Medium susceptible zones make up 4.2% of the area with 17.7% of the total landslides.The rest of the area was classified into high and very high categories,which makes up 3.9% of the area with corresponding 73.3% of the total landslides.Although the susceptibility map can reveal the likelihood of future landslides and debris flows,and it is helpful for the rebuilding process and future zoning issues.     

GIS-based earthquake-triggered landslide hazard zoning using contributing weight model

Earthquake-triggered landslides have aroused widespread attention because of their tremendous ability to harm people's lives and properties.The best way to avoid and mitigate their damage is to develop landslide hazard maps and make them available to the public in advance of an earthquake.Future construction can then be built according to the level of hazard and existing structures can be retrofit as necessary.During recent years various approaches have been made to develop landslide hazard maps using statistical analysis or physical models.However,these methods have limitations.This study introduces a new GIS-based approach,using the contributing weight model,to evaluate the hazard of seismically-induced landslides.In this study,the city and surrounding area of Dujiangyan was selected as the research area because of its moderate-high seismic activity.The parameters incorporated into the model that related to the probability of landslide occurrence were:slope gradient,slope aspect,geomorphology,lithology,base level,surface roughness,earthquake intensity,fault proximity,drainage proximity,and road proximity.The parameters were converted into raster data format with a resolution of 25×25m2 pixels.Analysis of the GIS correlations shows that the highest earthquake-induced landslide hazard areas are mainly in the hills and in some of the moderately steep mountainous areas of central Dujiangyan.The highest hazard zone covers an area of 11.1% of the study area,and the density distribution of seismically-induced landslides was 3.025/km2 from the 2008 Wenchuan earthquake.The moderately hazardous areas are mainly distributed within the moderately steep mountainous regions of the northern and southeastern parts of the study area and the hills of the northeastern part;covering 32.0% of the study area and with a density distribution of 2.123/km2 resulting from the Wenchuan earthquake.The lowest hazard areas are mainly distributed in the topographically flat plain in the northeastern part and some of the relatively gently slopes in the moderately steep mountainous areas of the northern part of Dujiangyan and the surrounding area.The lowest hazard areas cover 56.9% of the study area and exhibited landslide densities of 0.941/km2 and less from the Wenchuan earthquake.The quality of the hazard map was validated using a comparison with the distribution of landslides that were cataloged as occurring from the Wenchuan earthquake.43.1% of the study area consists of high and moderate hazardous zones,and these regions include 83.5% of landslides caused by the Wenchuan earthquake.The successful analysis shows that the contributing weight model can be effective for earthquake-triggered landslide hazard appraisal.The model's results can provide the basis for risk management and regional planning is.     

Activity evolution of landslides and debris flows after the Wenchuan earthquake in the Qipan catchment,Southwest China

The Wenchuan earthquake that occurred on 12 May 2008 induced numerous landslides. Loose landslide materials were deposited on hillslopes, and deep channels were easily remobilized and transformed into debris flows by extreme rainstorms. Twelve years after the Wenchuan earthquake, debris flows were still active in the Qipangou Ravine in the quake-hit area. In this paper, we continuously tracked the spatiotemporal evolution of the landslides and vegetation restoration and evaluated the evolution of debris flow activity in the Qipan catchment with the aid of a GIS platform and field investigations from 2008 to 2019. We observed that the area with active landslides increased sharply immediately following the earthquake, and then decreased with time; however, the total area of landslides continued to increase from 6.93 km2 in 2008 to 10.55 km2 in 2019. The active landslides shifted towards lower angles and higher elevations after 2013. Since 2009, the vegetation coverage has been gradually increasing and approaching the coverage present before the earthquake as of 2019. The landslide activity was high and the vegetation recovery rates were rapidly rising during the first five years after the earthquake; the recovery rates then slowed over time. Therefore, we divided the evolution that occurred during the post landslide period into an active period(2008-2013), a self-adjustment period(2013-2026) and a stable period(after 2026). We then proposed a quantitative model to determine the trends of landslide activity rates and NDVI values in the catchment, which indicated that the landslide activities and postseismic vegetation restoration rates in this catchment will return to preseismic levels within approximately two decades. We also analysed the runout volumes of the debris flows after the earthquakes(Diexi and Wenchuan) and the standard deviation of the vegetation coverage and predicted that the debris flow activities will last for an additional 50 years or more.     

A catastrophic debris flow in the Wenchuan Earthquake area,July 2013: characteristics,formation, and risk reduction

In the Wenchuan Earthquake area,many co-seismic landslides formed blocking-dams in debris flow channels. This blocking and bursting of landslide dams amplifies the debris flow scale and results in severe catastrophes. The catastrophic debris flow that occurred in Qipan gully(Wenchuan,Southwest China) on July 11,2013 was caused by intense rainfall and upstream cascading bursting of landslide dams. To gain an understanding of the processes of dam bursting and subsequent debris flow scale amplification effect,we attempted to estimate the bursting debris flow peak discharges along the main gully and analyzed the scale amplification process. The results showed that the antecedent and triggering rainfalls for 11 July debris flow event were 88.0 mm and 21.6 mm,respectively. The event highlights the fact that lower rainfall intensity can trigger debris flows after the earthquake. Calculations of the debris flow peak discharge showed that the peak discharges after the dams-bursting were 1.17–1.69 times greater than the upstream peak discharge. The peak discharge at the gully outlet reached 2553 m~3/s which was amplified by 4.76 times in comparison with the initial peak discharge in the upstream. To mitigate debris flow disasters,a new drainage channel with a trapezoidal V-shaped cross section was proposed. The characteristic lengths(h1 and h2) under optimal hydraulic conditions were calculated as 4.50 m and 0.90 m,respectively.     

Forecast method of multimode system for debris flow risk assessment in Qingping Town, Sichuan Province, China

The Wenchuan Earthquake of May 12,2008 triggered large numbers of geo-hazards.The heavy rain on 13 August 2010 triggered debris flows with total volume of more than 6 million cubic meters and the debris flows destroyed 500 houses and infrastructure built after the Wenchuan Earthquake.The study area Qingping Town was located in the northwestern part of the Sichuan Basin of China,which needs the second reconstructions and the critical evaluation of debris flow.This study takes basin as the study unit and defines collapse,landslide and debris flow hazard as a geo-hazard system.A multimode system composed of principal series system and secondary parallel system were established to evaluate the hazard grade of debris flow in 138 drainage basins of Qingping Town.The evaluation result shows that 30.43% of study basins(42 basins) and 24.58% of study area,are in extremely high or high hazard grades,and both percentage of basin quantity and percentage of area in different hazard grades decrease with the increase of hazard grade.According to the geo-hazard data from the interpretation of unmanned plane image with a 0.5-m resolution and field investigation after the Wenchuan Earthquake and 8.13 Big Debris Flow,the ratio of landslides and collapses increased after the Wenchuan Earthquake and the ratios of extremely high or high hazard grades were more than moderate or low hazard grades obviously.23 geo-hazards after8.13 Big Debris Flow in Qingping town region all occurred in basins with extremely high or high hazard grades,and 9 debris flows were in basins with extremely high hazard grade.The model of multimode system for critical evaluation could forecast not only the collapse and landslide but also the debris flow precisely when the basin was taken as the study unit.     

Characteristics and failure mechanism of an ancient earthquake-induced landslide with an extremely wide distribution area

The Lamuajue landslide is located in Lamuajue village on the right bank of the Meigu River,Sichuan Province, China. This landslide is an ancient landslide with an extremely wide distribution area,covering an area of 19 km~2 with a maximum width of5.5 km and an estimated residual volume of 3×10~8 m~3.The objectives of this study were to identify the characteristics and failure mechanism of this landslide. In this study,based on field investigations,aerial photography, and profile surveys, the boundary,lithology, structure of the strata, and characteristics of the landslide deposits were determined. A gently angled weak interlayer consisting of shale was the main factor contributing to the occurrence of the Lamuajue landslide. The deposition area can be divided into three zones: zone A is an avalanche deposition area mainly composed of blocks,fragments, and debris with diameters ranging from0.1 m to 3 m; zone B is a residual integrated rock mass deposition area with large blocks,boulders and "fake bedrock"; and zone C is a deposition zone of limestone blocks and fragments. Three types of failure mechanism were analyzed and combined to explain the Lamuajue landslide based on the features of the accumulation area. First, a shattering-sliding mechanism caused by earthquakes in zone A. Second,a sliding mechanism along the weak intercalation caused by gravity and water in zone B. Third,a shattering-ejection mechanism generated by earthquakes in zone C. The results provide a distinctive case for the study of gigantic landslides induced by earthquakes, which is very important for understanding and assessing ancient earthquakeinduced landslides.     

The disastrous 23 July 2009 debris flow in Xiangshui Gully, Kangding County, Southwestern China

On 23 July 2009, a catastrophic debris flows were triggered by heavy rainfall in Xiangshui gully, Kangding county, southwestern China. This debris flow originating shortly after a rainstorm with an intensity of 28 mm per hour transported a total volume of more than 480×103 m3 debris, depositing the poorly sorted sediment including boulders up to 2-3 m in diameter both onto an existing debris fans and into the river. Our primary objective for this study was to analyze the characteristics of the triggering ra...     

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City,China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow,resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as "instability-translational slide-tension fracture-collapse" and the formation mechanism as "translational landslide induced by heavy rainfall". The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research onpotential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.     

Case history of the disastrous debris flows of Tianmo Watershed in Bomi County,Tibet, China: Some mitigation suggestions

Debris flows and landslides, extensively developing and frequently occurring along Parlung Zangbo, seriously damage the Highway from Sichuan to Tiebt(G318) at Bomi County. The disastrous debris flows of the Tianmo Watershed on Sept. 4, 2007, July 25, 2010 and Sept. 4, 2010, blocked Parlung Zangbo River and produced dammed lakes, whose outburst flow made 50 m high terrace collapse at the opposite bank due to intense scouring on the foot of the terrace. As a result, the traffic was interrupted for 16 days in 2010 because that 900 m highway base was destructed and 430 m ruined. These debris flows were initiated by the glacial melting which was induced by continuous higher temperature and the following intensive rainfall, and expanded by moraines along channels and then blocked Parlung Zangbo. At the outlet of watershed,the density, velocity and peak discharge of debris flow was 2.06 t/m3, 12.7 m/s and 3334 m3/s, respectively. When the discharge at the outlet and the deposition volume into river exceeds 2125 m3/s and 126×103 m3, respectively, debris flow will completely blocked Parlung Zangbo. Moreover,if the shear stress of river flow on the foot of terrace and the inclination angel of terrace overruns 0. 377 N/m2 and 26°, respectively, the unconsolidated terrace will be eroded by outburst flow and collapse. It was strongly recommended for mitigation that identify and evade disastrous debris flows, reduce the junction angel of channels between river and watershed, build protecting wall for highway base and keep appropriate distance between highway and the edge of unconsolidated terrace.     

Susceptibility assessment of landslides caused by the wenchuan earthquake using a logistic regression model

The Wenchuan earthquake on May 12, 2008 caused numerous collapses, landslides, barrier lakes, and debris flows. Landslide susceptibility mapping is important for evaluation of environmental capacity and also as a guide for post-earthquake reconstruction. In this paper, a logistic regression model was developed within the framework of GIS to map landslide susceptibility. Qingchuan County, a heavily affected area, was selected for the study. Distribution of landslides was prepared by interpretation of multi-temporal and multi-resolution remote sensing images (ADS40 aerial imagery, SPOT5 imagery and TM imagery, etc.) and field surveys. The Certainly Factor method was used to find the influencial factors, indicating that lithologic groups, distance from major faults, slope angle, profile curvature, and altitude are the dominant factors influencing landslides. The weight of each factor was determined using a binomial logistic regression model. Landslide susceptibility mapping was based on spatial overlay analysis and divided into five classes. Major faults have the most significant impact, and landslides will occur most likely in areas near the faults. Onethird of the area has a high or very high susceptibility, located in the northeast, south and southwest, including 65.3% of all landslides coincident with the earthquake. The susceptibility map can reveal the likelihood of future failures, and it will be useful for planners during the rebuilding process and for future zoning issues.     

Geomorphologic analysis and physico-dynamic characteristics of Zhatai-Gully debris flows in SW China

Zhatai gully is a typical debris flow channel in Butuo county of Sichuan province, southwestern China. The geomorphologic features are analyzed and the physical-dynamic characteristics are discussed on the basis of field investigation and laboratory tests. Geomorphologic analysis indicates that Zhatai-gully drainage in relation to debris flow can be divided into source area, transport area, and deposition area. The source area has a steep slope and has very limited vegetation cover, which favors runoff, allowing loose solid materials to be mobilized easily and rapidly. In the transport area, there are many small landslides, lateral lobes, and loose materials distributed on both banks. These landslides are active and constantly providing abundant source of soils for the debris flows. In the deposition area, three old debris-flow deposits of different ages can be observed. The dynamic calculation shows that within the recurrence intervals of 50 and 100 years, debris flow discharges are 155.77m³/s and 1y8.19m³/s and deposition volumes are 16.39 x 10⁴ m³ and 18.14 x 10⁴ m³, respectively. The depositional fan of an old debris flow in the outlet of the gully can be subdivided into six layers. There are three debris flow deposits on left and two on the right side of the gully. Grain-size tests of sediments from the soil, gulley bed deposits, and the fresh and old debris flow deposits showed that high amounts of clay and fine gravel were derived from the soil in the source area whereas much of the gravel fraction were sourced from the gully bed deposits. Comprehensive analysis indicates that Zhatai gully is viscous debris-flow gully with moderate to high frequency and moderate to large magnitude debris flows. The risk of a debris flow disaster in Zhatai-gully is moderate and poses a potential threat to the planned hydroelectric dam. Appropriate engineering measures are suggested in the construction and protection of the planned hydroelectric station.     

Monitoring and warning of landslides and debris flows using an optical fiber sensor technology

Landslides and debris flows are typical geo-hazards which occur in hilly or mountainous regions. Debris flows may result from landslides. Geotechnical instrumentation plays an important role in monitoring and warning of landslides and resulted debris flows. Traditional technologies for monitoring landslides and debris flows have certain limitations. The new optical fiber sensors presented in this paper can overcome those limitations. This paper presents two new optical fiber sensor systems: one is the Fiber Bragg Grating (FBG)-based in-place inclinometer for monitoring landslides and the other is the FBG-based column-net system for monitoring debris flows. This paper presents the calibration results of FBG-based in-place inclinometers in laboratory. It is found that the calibration results are in good agreement with theoretical results. Both the FBG-based in-place inclinometers and the FBG-based column-net system have been installed at a site in Weijiagou valley, Beichuan County, Sichuan Province of China. Some preliminary results have been obtained and reported in the paper. The advantages of the FBG monitoring systems and their potential applications are also presented.     

Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China

Long-term kinematic research of slowmoving debris slide is rare despite of the widespread global distribution of this kind. This paper presents a study of the kinematics and mechanism of the Jinpingzi debris slide located on the Jinsha river bank in southwest China. This debris slide is known to have a volume of 27×106 m3 in active state for at least one century. Field survey and geotechnical investigation were carried out to define the structure of the landslide. The physical and mechanical properties of the landslide materials were obtained by in-situ and laboratory tests. Additionally, surface and subsurface displacements, as well as groundwater level fluctuations, were monitored since 2005. Movement features, especially the response of the landslide movement to rainfall, were analysed. Relationships between resisting forces and driving forces were analysed by using the limit equilibrium method assuming rigid-plastic frictional slip. The results confirmed a viscous component in the long-termcontinuous movement resulting in the quasioverconsolidated state of the slip zone with higher strength parameters than some other types of slowmoving landslides. Both surface and subsurface displacements showed an advancing pattern by the straight outwardly inclined(rather than gently or reversely inclined) slip zone, which resulted in low resistance to the entire sliding mass. The average surface displacement rate from 2005 to 2016 was estimated to be 0.19~0.87 mm/d. Basal sliding on the silty clay seam accounted for most of the deformation with different degrees of internal deformation in different parts. Rainfall was the predominant factor affecting the kinematics of Jinpingzi landslide while the role of groundwater level, though positive, was not significant. The response of the groundwater level to rainfall infiltration was not apparent. Unlike some shallow slow-moving earth flows or mudslides, whose behaviors are directly related to the phreatic groundwater level, the mechanism for Jinpingzi landslide kinematics is more likely related to the changing weight of the sliding mass and thedownslope seepage pressure in the shallow soil mass resulting from rainfall events.     

Landslide and basin self-organized criticality in the Lushan Hot Spring area

Defining a basin under a critical state(or a self-organized criticality) that has the potential to initiate landslides,debris flows,and subsequent sediment disasters,is a key issue for disaster prevention.The Lushan Hot Spring area in Nantou County,Taiwan,suffered serious sediment disasters after typhoons Sinlaku and Jangmi in 2008,and following Typhoon Morakot in 2009.The basin’s internal slope instability after the typhoons brought rain was examined using the landslide frequency-area distribution.The critical state indices attributed to landslide frequency-area distribution are discussed and the marginally unstable characteristics of the study area indicated.The landslides were interpreted from Spot 5 images before and after disastrous events.The results of the analysis show that the power-law landslide frequency-area curves in the basin for different rainfall-induced events tend to coincide with a single line.The temporal trend of the rainfallinduced landslide frequency-area distribution shows 1/f noise and scale invariance.A trend exists for landslide frequency-area distribution in log-log space for larger landslides controlled by the historical maximum accumulated rainfall brought by typhoons.The unstable state of the basin,including landslides,breached dams,and debris flows,are parts of the basin’s self-organizing processes.The critical state of landslide frequency-area distribution could be estimated by a critical exponent of 1.0.The distribution could be used for future estimation of the potential landslide magnitude for disaster mitigation and to identify the current state of a basin for management.     

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.     

Empirical-statistical models based on remote sensing for estimating the volume of landslides induced by the Wenchuan earthquake

The Wenchuan Ms 8.0 earthquake on May 12, 2008 induced a huge number of landslides. The distribution and volume of the landslides are very important for assessing risks and understanding the landslide - debris flow - barrier lake - bursts flood disaster chain. The number and the area of landslides in a wide region can be easily obtained by remote sensing technique, while the volume is relatively difficult to obtain because it requires some detailed geometric information of slope failure surface and sub-surface. Different empirical models for estimating landslide volume were discussed based on the data of 107 landslides in the earthquake-stricken area. The volume data of these landslides were collected by field survey. Their areas were obtained by interpreting remote sensing images while their apparent friction coefficients and height were extracted from the images unifying DEM (digital elevation model). By analyzing the relationships between the volume and the area, apparent friction coefficients, and the height, two models were established, one for the adaptation of a magnitude scale landslide events in a wide range of region, another for the adaptation in a small scope. The correlation coefficients (R2) are 0.7977 and 0.8913, respectively. The results estimated by the two models agree well with the measurement data.     

Risk assessment of secondary geological disasters induced by the Yushu earthquake

The Yushu Ms 7.1 earthquake occurred on April 14,2010 in Qinghai Province,China.It induced a mass of secondary geological disasters,such as collapses,landslides,and debris flows.Risk assessment maps are important for geological disaster prevention and mitigation,and also can serve as a guide for post-earthquake reconstruction.Firstly,a hazard assessment index system of secondary geological disasters in the earthquake region was built in this paper,which was based on detailed analysis of environmental and triggering factors closely related to geological disasters in the study area.GIS technology was utilized to extract and analyze the assessment index.Hazard assessment maps of secondary geological disasters were obtained by spatial modeling and overlaying analysis.Secondly,an analysis of the vulnerability of hazard bearing bodies in the area was conducted,important information,such as, population density,percentage of arable land, industrial and agricultural outputs per unit area were regarded as assessment indices to evaluate socioeconomic vulnerability.Thirdly,the risk level of secondary geological disasters of the area was obtained by the formula:Risk=Hazard×Vulnerability. Risk assessment maps were categorized into four levels,including"low","moderate","high"and"very high".These results show that some urban areas are at very high risk,including Jiegu,Chengwen,Xiaxiula and Sahuteng towns.This research can provide some references and suggestions to improve decisionmaking support for emergency relief and post- earthquake reconstruction in the study area.     

Impact of earthquake-induced landslide on the habitat suitability of giant panda in Wolong,China

Massive geological landslides and unstable landslide areas were triggered by the 2008 Wenchuan earthquake. These landslides caused deaths, damaged infrastructure and threatened endanger species. This study analyzed the impact of landslides on giant pandas and their habitats from the following aspects: threatening pandas‘ lives, damaging pandas‘ habitat, influencing giant panda behavior, increasing habitat fragmentation; the final aspect, and blocking gene flow by cutting off corridors. A habitat suitability map was created by integrating the landslide factors with other traditional factors based on a logistics regression method. According to the landslide inventory map, there are 1313 landslides, 818 rock debris flows, 117 rock avalanches and 43 mud flows occurred in the study area. A correlation analysis indicated that landslides caused the pandas to migrate, and the core landslides within 1 km2 had greater influence on panda migration. These core landslides primarily occurred in mid-altitude regionscharacterized by high slopes, old geological ages, large areas and large rock mass volumes. The habitat suitability assessment results for the Wolong Natural Reserve had better prediction performance(80.9%) and demonstrated that 14.5%, 15.9%, 20.5%, 47.6% and 1.5% of the study area can be classified as very high, high, moderate, low and very low giant panda suitability areas, respectively. This study can be used to inform panda and panda habitat research, management and protection during post-quake reconstruction and recovery periods in China.