This study investigated the failure mechanism associated with the rock mass structure and the dynamic fragmentation process of blocky rocks of the 2018 Daanshan rockslide that occurred on 11 August,2018.It was found t...This study investigated the failure mechanism associated with the rock mass structure and the dynamic fragmentation process of blocky rocks of the 2018 Daanshan rockslide that occurred on 11 August,2018.It was found that the initially collapsed rock of this rockslide was partitioned along the unconformity and strata interfaces.We analyzed how the unique rock mass structure,coupled with the road cut and the antecedent rainfall,jointly resulted in its failure.Based on the rock types and geological structures,the initial stratified configuration of a discrete element model was setup to reveal the influences of the local structure.The numerical model was divided into three parts.Part 1 is the basalt of the Nandaling Formation,the normal and shear stiffnesses of the basalt particles are set as 80 MPa and 40 MPa.Parts 2 and 3 are the sandstones interbedded with mudstone and sandstone of the Shihezi Formation,and the normal and shear stiffnesses of these parts were set as 6 MPa and 10 MPa,respectively.The dynamic process of the rockslide,particularly the rock fragmentation process,was numerically analyzed using a 3D discrete element method.The numerical results were compared with real-time videos and field investigations.The results show that the rock fragmentation and the final deposition range match well with the real disaster phenomenon,and the calculation accuracy of the rockslide reaches 82.41%.Moreover,a parameter sensitivity analysis was conducted,and classical uniform models under different bonding forces were established;the stratified model can better restore the true state of the fragmentation,movement,and deposition processes of rockslides.Therefore,for complicated rocks with significant differences in lithology,clarifying the rock mass stratigraphy is essential for an accurate reconstruction of the dynamic process of rockslides.展开更多
Making rural settlements of Mountainous Regions in Western Sichuan as the study objects and using symbolic statistical methods,then combining the case study of Daofu County,the paper analyzes the negative impact of th...Making rural settlements of Mountainous Regions in Western Sichuan as the study objects and using symbolic statistical methods,then combining the case study of Daofu County,the paper analyzes the negative impact of the scattered rural settlements on infrastructure construction,farm-ers' income increase and mountain ecological reconstruction in mountainous regions of western Sichuan. The results indicate that economic density is posi-tively related to both rural settlements density(R2=0.73) and rural population density(R2=0.77) ,and it is the same for relationship between towns density and rural settlements density(R2=0.88) and between towns density and eco-nomic density(R2=0.71) ,and the scattered distribution pattern of the rural settlements and shortage of economic centers is a major factor to the lagged socioeconomic development. On the eco-economic zoning to Daofu County,the paper indicates the spatial distribution model and the industrial develop-ment model of the rural settlements need to be changed,and rural population should be concentrated in larger rural settlements with development of off-farm industries while infrastructure construction is to reinforced.展开更多
Anatomical details are given in this article,which is per-formed by investigating the relationship between through the frangibility of mountain eco-environment and the status of irrational land-use in typical region o...Anatomical details are given in this article,which is per-formed by investigating the relationship between through the frangibility of mountain eco-environment and the status of irrational land-use in typical region of debris flow in Dongchuan district,Kunming city,yun-nan Province. This analysis is extended to the relationship between vi-cissitude of mountain disasters and the frangibility of mountain envi-ronment. The relatively coupling action of a vicious circle is a evolving characteristic by debris flow sand-gravel there. The eco-security is being faced with serious challenge. The tactics of eco-security has been con-structed since 1980s. Thus,the eco-environment can gradually be re-paired and optimized to achieve a fine circle.展开更多
As a discipline,the science of natural hazards and disaster risk aims to explain the spatial-temporal pattern,process and mechanism,emergency response and risk mitigation of natural hazards,which requires a multidisci...As a discipline,the science of natural hazards and disaster risk aims to explain the spatial-temporal pattern,process and mechanism,emergency response and risk mitigation of natural hazards,which requires a multidisci-plinary and interdisciplinary approach.With the support of Natural Science Finance of China(NSFC)and Chinese Academy of Sciences(CAS),in-depth research and systematic analysis on natural hazards and disaster risk were conducted.In this paper,the state of the art in research on natural hazards is summarized from seven aspects:formation process,mechanism and dynamic of natural hazards,disaster risk assessment,forecast,monitoring and early warning,disaster mitigation,emergency treatment and rescue,risk management and post-disaster re-construction.The trends within the natural hazards and disaster risk as a discipline were identified,along with existing shortcomings and significant gaps that need to be addressed.This paper highlighted:1)the scientific challenges including the frontier scientific issues and technological gaps on natural hazards and disaster risk dis-cipline from 2025 to 2035 in China,and 2)the proposal to develop a systemic and holistic natural hazards and disaster risk discipline.展开更多
On May 12, 2008, a magnitude 8.0 earthquake hit Wenchuan County, Sichuan Province resulted in great loss of life and properties.Besides, abundant landslides and slope failures were triggered in the most seriously hit ...On May 12, 2008, a magnitude 8.0 earthquake hit Wenchuan County, Sichuan Province resulted in great loss of life and properties.Besides, abundant landslides and slope failures were triggered in the most seriously hit areas and caused disastrous damages to infrastructures and public facilities.Moreover, abundant unstable slopes caused by the quake have the potential to cause damages for a considerable long period of time.The variety of these slopes and the corresponding treatments are connected with the topographical and geological conditions of the sites.It is decided to document and identify some of these major slope instabilities caused by the earthquake and their treatments.The paper shows the condition of a road in Dujiangyan through in situ explorations.The case history showed significant implications to the reconstruction of the quake-hit regions and future disaster prevention and management works.展开更多
A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eig...A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eighty-three people were killed or went missing and more than 103 houses were destroyed. In this paper, the geological conditions of the landslide are analyzed via field investigation and high-resolution imagery. The dynamic process and runout characteristics of the landslide are numerically analyzed using a depth-integrated continuum method and Mac Cormack-TVD finite difference algorithm.Computational results show that the evaluated area of the danger zone matchs well with the results of field investigation. It is worth noting that soil sprayed by the high-speed blast needs to be taken into account for such kind of large high-locality landslide. The maximum velocity is about 55 m/s, which is consistent with most cases. In addition, the potential danger zone of an unstable block is evaluated. The potential risk area evaluated by the efficient depthintegrated continuum method could play a significant role in disaster prevention and secondary hazard avoidance during rescue operations.展开更多
This paper describes a study on the combined impacts of antecedent earthquakes and droughts on disastrous debris flows.This is a novel attempt in quantifying such impacts using the effective peak acceleration(EPA)(to ...This paper describes a study on the combined impacts of antecedent earthquakes and droughts on disastrous debris flows.This is a novel attempt in quantifying such impacts using the effective peak acceleration(EPA)(to represent earthquakes) and standardized precipitation index(SPI)(to represent droughts).The study is based on the analysis of 116 disastrous debris flow events occurred in China's Mainland in the last 100 years covering a wide spectrum of climate types and landforms.It has been found that the combined impacts from earthquakes and droughts on disastrous debris flows do exist and vary from low to very high according to different climate conditions and terrains.The impacts from earthquakes increase with the increased terrain relief,and the impacts from droughts are strongest in semi-humid climate condition(with reduced impacts in humid and semi-arid /arid climate conditions).Hypothetical explanations on the study discoveries have been proposed.This study reveals the possible reasons for the disastrous debris flow distributions around the world and has significant implications in paleo-climate-seismicanalysis and disastrous debris flow risk management.展开更多
Abundant landslide deposits were triggered by the Wenchuan earthquake,providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions.A good understanding of the physical an...Abundant landslide deposits were triggered by the Wenchuan earthquake,providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions.A good understanding of the physical and mechanical properties of the landslide deposits is very important to the research on slope failure mechanisms and the initiation of debris flow.Laboratory biaxial compression tests are used to study the material compositions and water content impacts on the mechanical properties of landslide deposits,and a discrete element method(a bond-contact model)is used to study the particle stiffness,bond force,friction coefficient and confining stress impact on the mechanical behaviors and the relationships between the numerical and experimental parameters.The experimental results show that the failure stress of landslide deposits is decreased with increasing content of fine particles and also with increased water content,especially at the initial increasing stage.Cohesion of the saturated landslide deposits is increased,but the friction angle is decreased with the increase in the fine particle content.Shear strength parameters(the cohesion and friction angle)are decreased with the increasing water content at the initial increasing stage,and then,they slowly decrease.There is a critical value of the water content at 5%-7%(in weight)for the failure stress and shear strength parameters of the landslide deposits.Quadratic equations are presented to describe the relation between the bond force and cohesion,and the numerical friction coefficient and the experimental friction angle.展开更多
The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences ...The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper,we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth,the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress,and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition(Iverson and Ouyang,2015) is presented. In this formula,the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe's Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.展开更多
Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region,Southwest China. Quantitative study of the complicated surface ...Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region,Southwest China. Quantitative study of the complicated surface morphology of soil cracks is a prerequisite for further studies of soil-cracking mechanisms. The present paper establishes a quantitative indicator system by application of concepts and methods originating from Fractal Geometry and Network Analysis. These indicators can effectively express the complicated features of soil-crack network structure. Furthermore,a series of values related to soil-crack morphology was obtained by image processing on field photos of soil-crack quads,and gradation criteria for the degree of development of soil cracks were determined. Finally,the changes in values of the morphological indicators under different degrees of development were analyzed in detail. Our results indicate that (1) the degree of development of soil cracks can be divided into five grades,i.e.,feeble development,slight development,medium development,intensive development and extremely intensive development; (2) the values of the indicators change predictably with increasing degree of development of soil cracks. The area density (Dc) increases,and both the area-weighted mean ratio of crack area to perimeter (AWMARP),which reflects the intensity of cracking,and the index r,which is related to the connectivity of a soil crack,grow uniformly (albeit with different forms). AWMRAP increases at a geometric rate while r shows logarithm-mic growth,indicating a gradual increase in theconnectivity of a soil crack. Nevertheless,the area-weighted mean of soil-crack fractal dimension (AWMFRAC) shows a decreasing trend,indicating a gradual decline in the complexity of cracks as area density increases.展开更多
Supported by the spatial analysis feature of geographic information science and assessment model of regional debris flows,hazards degrees of the debris flows in the Upper Yangtze River Watershed(UYRW) are divided into...Supported by the spatial analysis feature of geographic information science and assessment model of regional debris flows,hazards degrees of the debris flows in the Upper Yangtze River Watershed(UYRW) are divided into five grades based on grid cell. The area of no danger,light danger,medium danger,severe danger and extreme severe danger regions respectively are 278 000,288 000,217 000,127 000,15 000 km2. Furthermore,the counties in the UYRW are classified into four classes based on the hazards degrees in each county. The number of severe danger,medium danger,light danger and no danger counties respectively are 49,82,77 and 105. The assessment results will be provided for the haz-ards forecasting and mitigation in the UYRW and ongoing region-alization of Main Function Regions in China as data and technique framework.展开更多
Abnormal glacier movement is likely to result in canyon-type hazards chain,such as the barrier lake of Yarlung Zangbo Grand Canyon formed by glacier debris flow in October 2018 in China.Glacier hazard usually evolves ...Abnormal glacier movement is likely to result in canyon-type hazards chain,such as the barrier lake of Yarlung Zangbo Grand Canyon formed by glacier debris flow in October 2018 in China.Glacier hazard usually evolves from the glacier surge and may occur in a regular cycle.Understanding the characteristics and process of glacier surge is important for early hazard recognition and hazard assessment.Based on field investigations,remote sensing interpretations and SAR offset-tracking surveys,this study confirms a typical glacier surge in the northeast Pamir,and presents its characteristics and processes."Black ice"mixed moraines choking uplift and overflowing lateral marine are the most important scenic characteristics,which were formed under the conditions of stagnant glacier downstream and abundant super-glacial moraine.Glacier movement event can be divided into a five-period cycle including quiescent,inoculation,initiation,fracture and decline.This surge event lasted for about 300 days,initiated in February 2015 developed extensive fracturing zone in spring and early summer at maximum velocity of 10±0.95 m/day,declined after August 2015 and recovered to quiescent status in October 2015 for the next inoculation.The average height of glacier"receiving"area increased by 20-40 m with 2.7-3.6×10^8 m^3 ice transferred from glacier"reservoir",and this volume accumulation again require 50-100 years for glacier mass balance which gives approximately 100 years frequency of the glacier surge.Nevertheless,long-period increase of precipitation and temperature were favorable for the occurrence,hydrological instability is the direct triggering mechanism,and while the Glacier Lake Outburst Flood(GLOF)hazards are unlikely to occur with this surge.展开更多
Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morpholo...Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morphological indicators, and analyzes the soil crack's morpho-logical features under various development degrees. By statistic analysis, three quantitative indicators for surface morphology are selected, namely soil crack area density, area weighted mean fractal dimension and connectivity index R, which can not only express the development intensity of soil cracks, but also effectively describe its morphological complexity and connectivity. The research results set a good base for the establishment of soil crack assessment system in Yuanmou arid-hot valley region.展开更多
Some of the remarkable characteristics of natural landslides, such as surprisingly long travel distances and high velocities, have been attributed to the mechanisms of frictional heating and thermal pressurization. In...Some of the remarkable characteristics of natural landslides, such as surprisingly long travel distances and high velocities, have been attributed to the mechanisms of frictional heating and thermal pressurization. In this work, this mechanism is combined with a depth-averaged model to simulate the long runout of landslides in the condition of deformation. Some important factors that influence frictional heating and thermal pressurization within the shear zone are further considered, including velocity profile and pressurization coefficient. In order to solve the coupled equations, a combined computational method based on the finite volume method and quadratic upwind interpolation for convective kinematics scheme is proposed. Several numerical tests are performed to demonstrate the feasibility of the computational scheme, the influence of thermal pressurization on landslide run-out, and the potential of the model to simulate an actual landslide.展开更多
Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and N...Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya(mostly small and medium size landslides in east-west direction) and the TransitionBelt(mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfallinduced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000 m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum(Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations(2000~3000 m) and steeper slopes(40°~50°).展开更多
Debris flows consist of grains of various sizes ranging from 10^(-6) m ～1 m. Field observations in the Jiangjia Gully (JJG) and other sites throughout China indicate that the grain size distribution of sediment in de...Debris flows consist of grains of various sizes ranging from 10^(-6) m ～1 m. Field observations in the Jiangjia Gully (JJG) and other sites throughout China indicate that the grain size distribution of sediment in debris flows can be characterized by an exponential function fit to the cumulative distribution. The exponent value for the function varies by location and may be useful in distinguishing between debris flows from different valleys. For example, minimum values and ranges of the exponent are associated with the high frequency of debris flows in the JJG. Furthermore, the distribution presents piecewise fractality (i.e. scaling laws hold in various ranges of the grain size) and we propose that the fractal structure determines the matrix and that the fractal dimension plays a crucial role in material exchange between a debris flow and the substrate it flows over. Finally, the empirical data support an exponential relation between grain composition and non-dimensional shear stress for the critical state of the channel. Overall we propose a material-determinism approach to studying debris flows which contrasts with the enviro-determinism that has dominated much recent work in this field.展开更多
Natural damming of rivers by mass movements is a very common and potentially dangerous phenomena which has been documented all over the world. In this paper, a two-layer model of Savage-Hutter type is presented to sim...Natural damming of rivers by mass movements is a very common and potentially dangerous phenomena which has been documented all over the world. In this paper, a two-layer model of Savage-Hutter type is presented to simulate the dynamic procedure for the intrusion of landslide into rivers. The two-layer shallow water system is derived by depth averaging the incompressible Navier-Stokes equations with the hydrostatic assumption. A high order accuracy scheme based on the finite volume method is proposed to solve the presented model equations. Several numerical tests are performed to verify the realiability and feasibility of the proposed model. The numerical results indicate that the proposed method can be competent for simulating the dynamic process of landslide intrusion into the river. The interaction effect between both layers has a significant impact on the landslide movement, water fluctuation and wave propagation.展开更多
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 1...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.展开更多
Landslides distribute extensively in Rongxian county, the southeast of Guangxi province, China and pose great threats to this county. At present, hazard management strategy is facing an unprecedented challenge due to ...Landslides distribute extensively in Rongxian county, the southeast of Guangxi province, China and pose great threats to this county. At present, hazard management strategy is facing an unprecedented challenge due to lack of a landslide susceptibility map. Therefore, the purpose of this paper was to construct a landslide susceptibility map by adopting three widely used models based on an integrated understanding of landslide’s characteristics.These models include a semi-quantitative method(SQM), information value model(IVM) and logistical regression model(LRM).The primary results show that(1) the county is classified into four susceptive regions, named as very low, low, moderate and high, which covered an area of 13.43%, 32.40%, 31.19% and 22.99% in SQM, 0.86%, 26.82%, 44.11%, and 28.21% in IVM, 9.88%, 17.73%, 46.36% and 26.03% in LRM;(2) landslides are likely to occur within the areas characterized by following obvious aspects: high intensity of human activities, slope angles of 25°～35°, the thickness of weathered soil is larger than 15 m; the lithology is granite, shale and mud rock;(3) the area under the curve of SQM, IVM and LRM is 0.7151, 0.7688 and 0.7362 respectively, and the corresponding success rate is 71.51%, 76.88% and 73.62%. It is concluded that these three models are acceptable because they have an effective capability of susceptibility assessment and can achieve an expected accuracy. In addition, the susceptibility outcome obtained from IVM provides a slightly higher quality than that from SQM, LRM.展开更多
The objective of the study reported here was to determine whether LANDSAT TM images could be used to quantify changes in land-use and ecosystem services in Yuanmou County. The sizes of six land use/land cover(LUCC) ca...The objective of the study reported here was to determine whether LANDSAT TM images could be used to quantify changes in land-use and ecosystem services in Yuanmou County. The sizes of six land use/land cover(LUCC) categories were estimated in Yuanmou County according to the LANDSAT TM images in the summer of 1986 and 2005. Coefficients published by Xie Gaodi and co-workers in 2003 were used to value changes in ecosystem services delivered by each land use/land cover category,and the ecosystem services sensitivity analysis was conducted to de-termine the effect of manipulating these coefficients on the estimated values. The im-portant results are summarized as followings. ① The estimated size of cultivated land,pasture land,water area and unused land decreased by 6.39%,1.35%,2.25% and 10.67% respectively between 1986 and 2005. By contrast,the estimated size of forest land and construction land increased by about 2.23% and 71.15% respectively between 1986 and 2005. ② The total ecosystem services value(EVS) of the study area in-creased from 2 142 132 609.46 yuan to 2 146 416 621.00 yuan,with the net increase of 4 284 011.54 yuan during the 20-year time period. ③ The coefficient sensitivity(CS) of the study are less than unity in all cases(CS ∧1) . This indicates that the total eco-system values estimated for the study area are relatively inelastic with respect to the ecosystem service coefficients. While this implies that our estimates are robust and the coefficient is reasonable,highly under or over valued coefficients can substantially affect the veracity of estimated changes in ecosystem service values overtime even when the CS are less than unity(CS ∧1) .展开更多
基金funded by the Strategic Priority Research Program of CAS(Grant No.XDA23090303)the NSFC(Grant No.42022054)+1 种基金Sichuan Science and Technology Program(Grant No.2022YFS0543)the Science Foundation for Distinguished Young Scholars of Sichuan Province(Grant No.2020JDJQ0044)State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(SKLGP2019Z013).
文摘This study investigated the failure mechanism associated with the rock mass structure and the dynamic fragmentation process of blocky rocks of the 2018 Daanshan rockslide that occurred on 11 August,2018.It was found that the initially collapsed rock of this rockslide was partitioned along the unconformity and strata interfaces.We analyzed how the unique rock mass structure,coupled with the road cut and the antecedent rainfall,jointly resulted in its failure.Based on the rock types and geological structures,the initial stratified configuration of a discrete element model was setup to reveal the influences of the local structure.The numerical model was divided into three parts.Part 1 is the basalt of the Nandaling Formation,the normal and shear stiffnesses of the basalt particles are set as 80 MPa and 40 MPa.Parts 2 and 3 are the sandstones interbedded with mudstone and sandstone of the Shihezi Formation,and the normal and shear stiffnesses of these parts were set as 6 MPa and 10 MPa,respectively.The dynamic process of the rockslide,particularly the rock fragmentation process,was numerically analyzed using a 3D discrete element method.The numerical results were compared with real-time videos and field investigations.The results show that the rock fragmentation and the final deposition range match well with the real disaster phenomenon,and the calculation accuracy of the rockslide reaches 82.41%.Moreover,a parameter sensitivity analysis was conducted,and classical uniform models under different bonding forces were established;the stratified model can better restore the true state of the fragmentation,movement,and deposition processes of rockslides.Therefore,for complicated rocks with significant differences in lithology,clarifying the rock mass stratigraphy is essential for an accurate reconstruction of the dynamic process of rockslides.
基金the Western China Program for Personnel Training of Chinese Academy of Sciences (L10416004)National Social Science Foundation of China (06BJY076)Knowledge Innovation Project Chinese Academy of Sciences
文摘Making rural settlements of Mountainous Regions in Western Sichuan as the study objects and using symbolic statistical methods,then combining the case study of Daofu County,the paper analyzes the negative impact of the scattered rural settlements on infrastructure construction,farm-ers' income increase and mountain ecological reconstruction in mountainous regions of western Sichuan. The results indicate that economic density is posi-tively related to both rural settlements density(R2=0.73) and rural population density(R2=0.77) ,and it is the same for relationship between towns density and rural settlements density(R2=0.88) and between towns density and eco-nomic density(R2=0.71) ,and the scattered distribution pattern of the rural settlements and shortage of economic centers is a major factor to the lagged socioeconomic development. On the eco-economic zoning to Daofu County,the paper indicates the spatial distribution model and the industrial develop-ment model of the rural settlements need to be changed,and rural population should be concentrated in larger rural settlements with development of off-farm industries while infrastructure construction is to reinforced.
基金the National Natural Science Foundation of China (40671026)
文摘Anatomical details are given in this article,which is per-formed by investigating the relationship between through the frangibility of mountain eco-environment and the status of irrational land-use in typical region of debris flow in Dongchuan district,Kunming city,yun-nan Province. This analysis is extended to the relationship between vi-cissitude of mountain disasters and the frangibility of mountain envi-ronment. The relatively coupling action of a vicious circle is a evolving characteristic by debris flow sand-gravel there. The eco-security is being faced with serious challenge. The tactics of eco-security has been con-structed since 1980s. Thus,the eco-environment can gradually be re-paired and optimized to achieve a fine circle.
基金This work was supported by the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-DQC006)the Major Program of National Natural Science Foundation of China(Grant No.41790432)+1 种基金the National Natural Science Foundation of China(Grant No.L1924041)Research Project on the Discipline Development Strategy of Academic Divisions of the Chinese Academy of Sciences(Grand No.XK2019DXC006).
文摘As a discipline,the science of natural hazards and disaster risk aims to explain the spatial-temporal pattern,process and mechanism,emergency response and risk mitigation of natural hazards,which requires a multidisci-plinary and interdisciplinary approach.With the support of Natural Science Finance of China(NSFC)and Chinese Academy of Sciences(CAS),in-depth research and systematic analysis on natural hazards and disaster risk were conducted.In this paper,the state of the art in research on natural hazards is summarized from seven aspects:formation process,mechanism and dynamic of natural hazards,disaster risk assessment,forecast,monitoring and early warning,disaster mitigation,emergency treatment and rescue,risk management and post-disaster re-construction.The trends within the natural hazards and disaster risk as a discipline were identified,along with existing shortcomings and significant gaps that need to be addressed.This paper highlighted:1)the scientific challenges including the frontier scientific issues and technological gaps on natural hazards and disaster risk dis-cipline from 2025 to 2035 in China,and 2)the proposal to develop a systemic and holistic natural hazards and disaster risk discipline.
基金supported by the 973 Program of China (Grant No. 2008CB425803the Open Fund of the Key Laboratory of Marine Geology and Environment, China Academy of Sciences (Grant No. MGE2008KG04)the Open Fund of the Key Laboratory of Mountain Hazards and Surface Process, CAS.
文摘On May 12, 2008, a magnitude 8.0 earthquake hit Wenchuan County, Sichuan Province resulted in great loss of life and properties.Besides, abundant landslides and slope failures were triggered in the most seriously hit areas and caused disastrous damages to infrastructures and public facilities.Moreover, abundant unstable slopes caused by the quake have the potential to cause damages for a considerable long period of time.The variety of these slopes and the corresponding treatments are connected with the topographical and geological conditions of the sites.It is decided to document and identify some of these major slope instabilities caused by the earthquake and their treatments.The paper shows the condition of a road in Dujiangyan through in situ explorations.The case history showed significant implications to the reconstruction of the quake-hit regions and future disaster prevention and management works.
基金Financial support from National Nature Science Foundation of China (Grant No. 41572303, 41520104002)Chinese Academy of Sciences “Light of West China” Program and Youth Innovation Promotion Association
文摘A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eighty-three people were killed or went missing and more than 103 houses were destroyed. In this paper, the geological conditions of the landslide are analyzed via field investigation and high-resolution imagery. The dynamic process and runout characteristics of the landslide are numerically analyzed using a depth-integrated continuum method and Mac Cormack-TVD finite difference algorithm.Computational results show that the evaluated area of the danger zone matchs well with the results of field investigation. It is worth noting that soil sprayed by the high-speed blast needs to be taken into account for such kind of large high-locality landslide. The maximum velocity is about 55 m/s, which is consistent with most cases. In addition, the potential danger zone of an unstable block is evaluated. The potential risk area evaluated by the efficient depthintegrated continuum method could play a significant role in disaster prevention and secondary hazard avoidance during rescue operations.
基金funded by the Ministry of Science and Technology of China (Grant No. 2011BAK12B02)the National Natural Science Foundation of China (Grant No. 41190084)+2 种基金the National Key Technology R&D Program (Grant No 2012 BAK10B04)the Non-Profit Industry Financial Program of MWR (Grant No. 201301058)the Changjiang River Scientific Research Institute of Sciences Innovation Team Project (Grant No. CKSF2012052/TB)
文摘This paper describes a study on the combined impacts of antecedent earthquakes and droughts on disastrous debris flows.This is a novel attempt in quantifying such impacts using the effective peak acceleration(EPA)(to represent earthquakes) and standardized precipitation index(SPI)(to represent droughts).The study is based on the analysis of 116 disastrous debris flow events occurred in China's Mainland in the last 100 years covering a wide spectrum of climate types and landforms.It has been found that the combined impacts from earthquakes and droughts on disastrous debris flows do exist and vary from low to very high according to different climate conditions and terrains.The impacts from earthquakes increase with the increased terrain relief,and the impacts from droughts are strongest in semi-humid climate condition(with reduced impacts in humid and semi-arid /arid climate conditions).Hypothetical explanations on the study discoveries have been proposed.This study reveals the possible reasons for the disastrous debris flow distributions around the world and has significant implications in paleo-climate-seismicanalysis and disastrous debris flow risk management.
基金support of the Key Deployment Project of the Chinese Academy of Sciences (KZZD-EW-05-01)the National Natural Science Foundation of China(41472272,41102194)+1 种基金the Opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology)(SKLGP2013K015)the Science Foundation for Excellent Youth Scholars of Sichuan University(2013SCU04A07)
文摘Abundant landslide deposits were triggered by the Wenchuan earthquake,providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions.A good understanding of the physical and mechanical properties of the landslide deposits is very important to the research on slope failure mechanisms and the initiation of debris flow.Laboratory biaxial compression tests are used to study the material compositions and water content impacts on the mechanical properties of landslide deposits,and a discrete element method(a bond-contact model)is used to study the particle stiffness,bond force,friction coefficient and confining stress impact on the mechanical behaviors and the relationships between the numerical and experimental parameters.The experimental results show that the failure stress of landslide deposits is decreased with increasing content of fine particles and also with increased water content,especially at the initial increasing stage.Cohesion of the saturated landslide deposits is increased,but the friction angle is decreased with the increase in the fine particle content.Shear strength parameters(the cohesion and friction angle)are decreased with the increasing water content at the initial increasing stage,and then,they slowly decrease.There is a critical value of the water content at 5%-7%(in weight)for the failure stress and shear strength parameters of the landslide deposits.Quadratic equations are presented to describe the relation between the bond force and cohesion,and the numerical friction coefficient and the experimental friction angle.
基金Financial support from NSFC(Grant No.41572303,4151001059,41101008)Key Projects in the National Science & Technology Pillar Program(2014BAL05B01)CAS "Light of West China" Program
文摘The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper,we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth,the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress,and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition(Iverson and Ouyang,2015) is presented. In this formula,the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe's Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.
基金supported by the National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (Grant No.2008BAD98B02, 2006BAC01A11)the Western Light Program of Talents Cultivating of CAS (2008)+1 种基金the National Natural Sciences Foundation of China (Grant No. 30470297)the Foundation of Key Laboratory of Mountain Hazards and Surface Process, CAS
文摘Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region,Southwest China. Quantitative study of the complicated surface morphology of soil cracks is a prerequisite for further studies of soil-cracking mechanisms. The present paper establishes a quantitative indicator system by application of concepts and methods originating from Fractal Geometry and Network Analysis. These indicators can effectively express the complicated features of soil-crack network structure. Furthermore,a series of values related to soil-crack morphology was obtained by image processing on field photos of soil-crack quads,and gradation criteria for the degree of development of soil cracks were determined. Finally,the changes in values of the morphological indicators under different degrees of development were analyzed in detail. Our results indicate that (1) the degree of development of soil cracks can be divided into five grades,i.e.,feeble development,slight development,medium development,intensive development and extremely intensive development; (2) the values of the indicators change predictably with increasing degree of development of soil cracks. The area density (Dc) increases,and both the area-weighted mean ratio of crack area to perimeter (AWMARP),which reflects the intensity of cracking,and the index r,which is related to the connectivity of a soil crack,grow uniformly (albeit with different forms). AWMRAP increases at a geometric rate while r shows logarithm-mic growth,indicating a gradual increase in theconnectivity of a soil crack. Nevertheless,the area-weighted mean of soil-crack fractal dimension (AWMFRAC) shows a decreasing trend,indicating a gradual decline in the complexity of cracks as area density increases.
基金The National Basic Research Program (973 program) (2002CB111506)the R&D Infrastructure and Facility Devel-opment Program (2005DKA32300)
文摘Supported by the spatial analysis feature of geographic information science and assessment model of regional debris flows,hazards degrees of the debris flows in the Upper Yangtze River Watershed(UYRW) are divided into five grades based on grid cell. The area of no danger,light danger,medium danger,severe danger and extreme severe danger regions respectively are 278 000,288 000,217 000,127 000,15 000 km2. Furthermore,the counties in the UYRW are classified into four classes based on the hazards degrees in each county. The number of severe danger,medium danger,light danger and no danger counties respectively are 49,82,77 and 105. The assessment results will be provided for the haz-ards forecasting and mitigation in the UYRW and ongoing region-alization of Main Function Regions in China as data and technique framework.
基金supported by the National Key R&D Program of China (2018YFC1505002)CGS Research Fund (JYYWF20181501)+1 种基金National Natural Science Foundation of China (41672359)Chinese Academy of Sciences President’s International Fellowship Initiative (grant No. 2018PC0009)
文摘Abnormal glacier movement is likely to result in canyon-type hazards chain,such as the barrier lake of Yarlung Zangbo Grand Canyon formed by glacier debris flow in October 2018 in China.Glacier hazard usually evolves from the glacier surge and may occur in a regular cycle.Understanding the characteristics and process of glacier surge is important for early hazard recognition and hazard assessment.Based on field investigations,remote sensing interpretations and SAR offset-tracking surveys,this study confirms a typical glacier surge in the northeast Pamir,and presents its characteristics and processes."Black ice"mixed moraines choking uplift and overflowing lateral marine are the most important scenic characteristics,which were formed under the conditions of stagnant glacier downstream and abundant super-glacial moraine.Glacier movement event can be divided into a five-period cycle including quiescent,inoculation,initiation,fracture and decline.This surge event lasted for about 300 days,initiated in February 2015 developed extensive fracturing zone in spring and early summer at maximum velocity of 10±0.95 m/day,declined after August 2015 and recovered to quiescent status in October 2015 for the next inoculation.The average height of glacier"receiving"area increased by 20-40 m with 2.7-3.6×10^8 m^3 ice transferred from glacier"reservoir",and this volume accumulation again require 50-100 years for glacier mass balance which gives approximately 100 years frequency of the glacier surge.Nevertheless,long-period increase of precipitation and temperature were favorable for the occurrence,hydrological instability is the direct triggering mechanism,and while the Glacier Lake Outburst Flood(GLOF)hazards are unlikely to occur with this surge.
基金the National Natural Science Foundation of China (30470297)the National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (2006BAC01A11)the Youth Foundation of Institute of Mountain Hazards and Environment of Chinese Academy of Sciences
文摘Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morphological indicators, and analyzes the soil crack's morpho-logical features under various development degrees. By statistic analysis, three quantitative indicators for surface morphology are selected, namely soil crack area density, area weighted mean fractal dimension and connectivity index R, which can not only express the development intensity of soil cracks, but also effectively describe its morphological complexity and connectivity. The research results set a good base for the establishment of soil crack assessment system in Yuanmou arid-hot valley region.
基金supported by the National Natural Science Foundation of China (Grant No. 41790433)NSFC-ICIMOD (Grant No. 41661144041)+1 种基金Key Research and Development Projects of Sichuan Province (2017SZ0041)CAS "Light of West China" Program
文摘Some of the remarkable characteristics of natural landslides, such as surprisingly long travel distances and high velocities, have been attributed to the mechanisms of frictional heating and thermal pressurization. In this work, this mechanism is combined with a depth-averaged model to simulate the long runout of landslides in the condition of deformation. Some important factors that influence frictional heating and thermal pressurization within the shear zone are further considered, including velocity profile and pressurization coefficient. In order to solve the coupled equations, a combined computational method based on the finite volume method and quadratic upwind interpolation for convective kinematics scheme is proposed. Several numerical tests are performed to demonstrate the feasibility of the computational scheme, the influence of thermal pressurization on landslide run-out, and the potential of the model to simulate an actual landslide.
基金supported by the National Natural Science Foundation of China(Grant No.41401007)the Key Research Program of the Chinese Academy of Sciences(Grant No.KZZD-EW-08-01)+1 种基金jointly supported by the Australian government funded Koshi Basin Programme at ICIMODICIMOD’s core funds contributed by the governments of Afghanistan,Australia,Austria,Bangladesh,Bhutan,China,India,Myanmar,Nepal,Norway,Pakistan,Switzerland,and theUnited Kingdom
文摘Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya(mostly small and medium size landslides in east-west direction) and the TransitionBelt(mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfallinduced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000 m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum(Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations(2000~3000 m) and steeper slopes(40°~50°).
基金This work is supported by National Science Foundation Grant No. 40671025 and 40501008；also by the Knowledge Innovation Project of Chinese Academy of Sciences, KZCX3-SW-352；the Frontier Project of Institute of Mountain Hazard and Environment, CAS, No. C3-200307. Special gratitude goes to Dr. He Yiping for field data for the JJG debris flow.
文摘Debris flows consist of grains of various sizes ranging from 10^(-6) m ～1 m. Field observations in the Jiangjia Gully (JJG) and other sites throughout China indicate that the grain size distribution of sediment in debris flows can be characterized by an exponential function fit to the cumulative distribution. The exponent value for the function varies by location and may be useful in distinguishing between debris flows from different valleys. For example, minimum values and ranges of the exponent are associated with the high frequency of debris flows in the JJG. Furthermore, the distribution presents piecewise fractality (i.e. scaling laws hold in various ranges of the grain size) and we propose that the fractal structure determines the matrix and that the fractal dimension plays a crucial role in material exchange between a debris flow and the substrate it flows over. Finally, the empirical data support an exponential relation between grain composition and non-dimensional shear stress for the critical state of the channel. Overall we propose a material-determinism approach to studying debris flows which contrasts with the enviro-determinism that has dominated much recent work in this field.
基金Financial support from the National Science Fund for Distinguished Young Scholars (Grant No.41225011)the NSFC (Grant No. 41272346)+1 种基金the Information technology project of the Department of transportation (2014364J03090)the STS project of Chinese Academy of Sciences (project No. KFJ-EW-STS-094)
文摘Natural damming of rivers by mass movements is a very common and potentially dangerous phenomena which has been documented all over the world. In this paper, a two-layer model of Savage-Hutter type is presented to simulate the dynamic procedure for the intrusion of landslide into rivers. The two-layer shallow water system is derived by depth averaging the incompressible Navier-Stokes equations with the hydrostatic assumption. A high order accuracy scheme based on the finite volume method is proposed to solve the presented model equations. Several numerical tests are performed to verify the realiability and feasibility of the proposed model. The numerical results indicate that the proposed method can be competent for simulating the dynamic process of landslide intrusion into the river. The interaction effect between both layers has a significant impact on the landslide movement, water fluctuation and wave propagation.
基金financially supported by the Open Research Fund from the Key Laboratory of Mountain Hazards and Earth Surface Process (Chinese Academy of Sciences) (Grant No.KLMHESP-17-06)the Independent Research Fund from the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology) (Grant No.40100-00002219)
文摘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.
基金funded by the National Natural Science Foundation of China (No. 51609041)the Natural Scientific Project of Guangxi Zhuang Autonomous Region (No. 2018GXNSFAA138187)+2 种基金the Project of the Education Department of Guangxi Zhuang Autonomous Region (No. 2018KY0027)the Project of Department of Land and Resources of Guangxi Zhuang Autonomous Region (GXZC2018G3-19302-JGYZ)the Project of Xi’an Geological survey center of China Geological survey (DD20189270)
文摘Landslides distribute extensively in Rongxian county, the southeast of Guangxi province, China and pose great threats to this county. At present, hazard management strategy is facing an unprecedented challenge due to lack of a landslide susceptibility map. Therefore, the purpose of this paper was to construct a landslide susceptibility map by adopting three widely used models based on an integrated understanding of landslide’s characteristics.These models include a semi-quantitative method(SQM), information value model(IVM) and logistical regression model(LRM).The primary results show that(1) the county is classified into four susceptive regions, named as very low, low, moderate and high, which covered an area of 13.43%, 32.40%, 31.19% and 22.99% in SQM, 0.86%, 26.82%, 44.11%, and 28.21% in IVM, 9.88%, 17.73%, 46.36% and 26.03% in LRM;(2) landslides are likely to occur within the areas characterized by following obvious aspects: high intensity of human activities, slope angles of 25°～35°, the thickness of weathered soil is larger than 15 m; the lithology is granite, shale and mud rock;(3) the area under the curve of SQM, IVM and LRM is 0.7151, 0.7688 and 0.7362 respectively, and the corresponding success rate is 71.51%, 76.88% and 73.62%. It is concluded that these three models are acceptable because they have an effective capability of susceptibility assessment and can achieve an expected accuracy. In addition, the susceptibility outcome obtained from IVM provides a slightly higher quality than that from SQM, LRM.
基金the National Natural Science Foundation of China (30470297)the "Western Light" Talents Training Program of Chinese Academy of Sciences 2005 (C20609090)
文摘The objective of the study reported here was to determine whether LANDSAT TM images could be used to quantify changes in land-use and ecosystem services in Yuanmou County. The sizes of six land use/land cover(LUCC) categories were estimated in Yuanmou County according to the LANDSAT TM images in the summer of 1986 and 2005. Coefficients published by Xie Gaodi and co-workers in 2003 were used to value changes in ecosystem services delivered by each land use/land cover category,and the ecosystem services sensitivity analysis was conducted to de-termine the effect of manipulating these coefficients on the estimated values. The im-portant results are summarized as followings. ① The estimated size of cultivated land,pasture land,water area and unused land decreased by 6.39%,1.35%,2.25% and 10.67% respectively between 1986 and 2005. By contrast,the estimated size of forest land and construction land increased by about 2.23% and 71.15% respectively between 1986 and 2005. ② The total ecosystem services value(EVS) of the study area in-creased from 2 142 132 609.46 yuan to 2 146 416 621.00 yuan,with the net increase of 4 284 011.54 yuan during the 20-year time period. ③ The coefficient sensitivity(CS) of the study are less than unity in all cases(CS ∧1) . This indicates that the total eco-system values estimated for the study area are relatively inelastic with respect to the ecosystem service coefficients. While this implies that our estimates are robust and the coefficient is reasonable,highly under or over valued coefficients can substantially affect the veracity of estimated changes in ecosystem service values overtime even when the CS are less than unity(CS ∧1) .
