Landslide susceptibility mapping of vicinity of Yaka Landslide (Gelendost,Turkey) using conditional probability approach in GIS

On 19 February 2007, a landslide occurred on the Alaard?ç Slope, located 1.6 km south of the town of Yaka (Gelendost, Turkey.) Subsequently, the displaced materials transformed into a mud flow in E?lence Creek and continued 750 m downstream towards the town of Yaka. The mass poised for motion in the Yaka Landslide source area and its vicinity, which would be triggered to a kinetic state by trigger factors such as heavy or sustained rainfall and/or snowmelt, poise a danger in the form of loss of life and property to Yaka with its population of 3,000. This study was undertaken to construct a susceptibility mapping of the vicinity of the Yaka Landslide’s source area and to relate it to movement of the landslide mass with the goal of prevention or mitigation of loss of life and property. The landslide susceptibility map was formulated by designating the relationship of the effecting factors that cause landslides such as lithology, gradient, slope aspect, elevation, topographical moisture index, and stream power index to the landslide map, as determined by analysis of the terrain, through the implementation of the conditional probability method. It was determined that the surface area of the Goksogut formation, which has attained lithological characteristics of clayey limestone with a broken and separated base and where area landslides occur, possesses an elevation of 1,100–1,300 m, a slope gradient of 15 °–35 ° and a slope aspect between 0 °–67.5 ° and 157 °–247 °. Loss of life and property may be avoided by the construction of structures to check the debris mass in E?lence Creek, the cleaning of the canal which passes through Yaka, the broadening of the canal’s base area, elevating the protective edges along the canal and the establishment of a protective zone at least 10-m wide on each side of the canal to deter against damage from probable landslide occurrence and mud flow.     

The environmental impact of landslides on the population living on the eastern footslopes of the Aberdare ranges in Kenya: a case study of Maringa Village landslide

 Landslides are a recognized but poorly studied phenomena in the eastern footslopes of the Aberdare ranges in central Kenya. The Aberdare ranges traverse the Murang'a, Kiambu, Nyeri and Nyandarua districts of Kenya where fatal landslides have occurred in the past. A detailed study of a major landslide which occurred at Maringa village in Murang'a district on 30 April 1997, has been undertaken. The landslide buried three houses at the toe of a slope and killed all the 11 occupants in their sleep. It is shown that the geology and climate of the study area contribute to the prevalence of landslides not only in Murang'a but in all the andosol-covered areas throughout the eastern footslopes of Aberdare ranges. Rapid weathering of pyroclastic rocks in a warm and wet climate create a regolith which is generally weaker than the underlying better-cemented basalt and basaltic agglomerates. The landsliding occurred when the weathered pyroclastic regolith become saturated after a heavy rainstorm on high mechanically unstable slope which slid over the more stable basalts. Over-saturation of clay soils (andosol) which were also derived from weathering of pyroclastic rocks contributed to the slope failure. The results of the study show that besides fatalities and injuries, the landslide destroyed homes, plantations and roads. Received: 16 March 1998 · Accepted: 22 September 1998     

An approach for GIS-based statistical landslide susceptibility zonation—with a case study in the Himalayas

Landslide susceptibility zonation (LSZ) is necessary for disaster management and planning development activities in mountainous regions. A number of methods, viz. landslide distribution, qualitative, statistical and distribution-free analyses have been used for the LSZ studies and they are again briefly reviewed here. In this work, two methods, the Information Value (InfoVal) and the Landslide Nominal Susceptibility Factor (LNSF) methods that are based on bivariate statistical analysis have been applied for LSZ mapping in a part of the Himalayas. Relevant thematic maps representing various factors (e.g., slope, aspect, relative relief, lithology, buffer zones along thrusts, faults and lineaments, drainage density and landcover) that are related to landslide activity, have been generated using remote sensing and GIS techniques. The LSZ derived from the LNSF method, has been compared with that produced from the InfoVal method and the result shows a more realistic LSZ map from the LNSF method which appears to conform to the heterogeneity of the terrain.     

Landslide susceptibility zonation mapping and its validation in part of Garhwal Lesser Himalaya, India, using binary logistic regression analysis and receiver operating characteristic curve method

A landslide susceptibility zonation (LSZ) map helps to understand the spatial distribution of slope failure probability in an area and hence it is useful for effective landslide hazard mitigation measures. Such maps can be generated using qualitative or quantitative approaches. The present study is an attempt to utilise a multivariate statistical method called binary logistic regression (BLR) analysis for LSZ mapping in part of the Garhwal Lesser Himalaya, India, lying close to the Main Boundary Thrust (MBT). This method gives the freedom to use categorical and continuous predictor variables together in a regression analysis. Geographic Information System has been used for preparing the database on causal factors of slope instability and landslide locations as well as for carrying out the spatial modelling of landslide susceptibility. A forward stepwise logistic regression analysis using maximum likelihood estimation method has been used in the regression. The constant and the coefficients of the predictor variables retained by the regression model have been used to calculate the probability of slope failure for the entire study area. The predictive logistic regression model has been validated by receiver operating characteristic curve analysis, which has given 91.7% accuracy for the developed BLR model.     

Understanding rainfall-landslide relationships in man-modified environments: a case-history from Caramanico Terme, Italy

 The expansion of Caramanico Terme in this century has led to the urbanization of marginally stable valley slopes, and this has coincided with the apparent acceleration of landslide processes. Recent landslides on man-modified slopes were caused, but not necessarily triggered, by heavy precipitation (antecedent moisture was a more critical factor than the amount of storm rainfall). Because no important landslides on natural slopes in the same period were reported in the Caramanico area, a clear distinction must be made between natural settings and those modified by man when determining rainfall thresholds for predictive purposes. In recently urbanized mountainous environments, the thresholds used to assess landslide hazards should not be weighted too heavily on old historical records of precipitation and associated mass movements. Instead, more weight ought to be given to the period following the occurrence of any major anthropogenic and natural (e.g. high-magnitude earthquake) modification of slope setting. Received: 19 October 1996 · Accepted: 25 June 1997     

Validation of Landslide Susceptibility Maps; Examples and Applications from a Case Study in Northern Spain

A procedure for validating landslide susceptibility maps wasapplied in a study area in northern Spain and the results obtained compared. Validationwas used to carry out sensitivity analysis for individual variables and combinationsof variables. The validity of different map-making methods was tested, as well as theutility of different types of Favourability Functions. The results obtained show thatvalidation is essential to determine the predictive value of susceptibility maps. Italso helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation based on a temporal strategy makes it possible to derive hazard maps from susceptibility maps.     

基于 GIS和 AHP的安康市滑坡地质灾害危险性评估

安康市滑坡崩塌频繁发生,对当地造成了不可估量的损失。以安康市地震小区划为依托,对当地滑坡地质灾害的易发性进行研究。在研究区进行野外踏勘和搜集资料的基础上,借助magis和arcgis平台强大的绘图、分析功能,运用层次分析法对滑坡灾害因子进行加权叠加计算,绘制滑坡灾害危险性区划图。区划结果分为四个等级：无危险区、低危险区、中危险区、高危险区。无危险区、低危险区滑坡灾害易发性较低,为适宜城市规划和项目实施工作地带,中危险区、高危险区则要加以治理以减少滑坡地质灾害对居民生命和财产的威胁。     

Landslide risk assessment using concepts of danger pixels and fuzzy set theory in Darjeeling Himalayas

Landslide risk assessment (LRA) is a key component of landslide studies. The landslide risk can be defined as the potential for adverse consequences or loss to human population and property due to the occurrence of landslides. The LRA can be regional or site-specific in nature and is an important information for planning various developmental activities in the area. LRA is considered as a function of landslide potential (LP) and resource damage potential (RDP). The LP and RDP are typically characterized by the landslide susceptibility zonation map and the resource map (i.e., land use land cover map) of the area, respectively. Development of approaches for LRA has always been a challenge. In the present study, two approaches for LRA, one based on the concept of danger pixels and the other based on fuzzy set theory, have been developed and implemented to generate LRA maps of Darjeeling Himalayas, India. The LRA map based on the first approach indicates that 1,015 pixels of habitation and 921 pixels of road section are under risk due to landslides. The LRA map derived from fuzzy set theory based approach shows that a part of habitat area (2,496 pixels) is under very high risk due to landslides. Also, another part of habitat area and a portion of road network (7,204 pixels) are under high risk due to landslides. Thus, LRA map based on the concept of danger pixels gives the pixels under different resource categories at risk due to landslides whereas the LRA map based on the concept of fuzzy set theory further refines this result by defining the degree of severity of risk to these categories by putting these into high and low risk zones. Hence, the landslide risk assessment study carried out using two approaches in this paper can be considered in cohesion for assessing the risks due to landslides in a region.     

Landslide risk analysis in the area North of Lisbon (Portugal): evaluation of direct and indirect costs resulting from a motorway disruption by slope movements

A risk analysis is developed for a test site located in the area north of Lisbon using a scenario of a temporary interruption of the motorway A9 due to a landslide of rotational or translational type. Landslide susceptibility is assessed at the regional scale independently for rotational and translational slides, comparing the landslide distribution with a set of assumed independent landslide predisposing factors. Susceptibility models are validated and classified through the computation of prediction rate curves based on the temporal partition of the landslide data sets. Landslide hazard maps are based on a scenario of future landslide occurrence for the next 27 years. These maps allow the definition of two critical areas on the motorway A9 with regards to landslide susceptibility. Direct costs associated with both critical spots are assessed taking into account the probable affected area of the motorway, and the reconstruction costs. Indirect costs derived from the traffic interruption are evaluated considering the alternatives paths to the motorway, and include costs resulting from: (1) additional fuel consumption; (2) decrease in tollgate income; and (3) loss of productive time. Results show that indirect costs may be 24 to 43 times higher than direct costs, assuming a temporary interruption of the motorway for 6 months.     

香丽高速公路边坡地质灾害发育特征与易发性区划

针对香丽高速公路边坡地质灾害,在详细的道路工程勘察设计文件的基础上,结合现场踏勘调查,系统地研究了其边坡地质灾害的主要类型、发育特征和分布规律;提出高速公路等线性工程边坡灾害的基本地质条件、自然诱发因素、人类工程活动和灾害历史记录等完整信息评价指标。采用层次分析法、专家评分法与因素累积法相结合的研究方法,建立了线性工程边坡地质灾害易发性评价模型,并基于GIS平台完成了香丽高速公路边坡地质灾害的易发性区划。为指导香丽高速公路地质灾害的危险性评价及科学防治提供了重要依据,对类似山区道路等线性工程边坡地质灾害危险性评价研究与实践具有一定的示范作用和参考价值。     

Regional hydrological thresholds for landslides and floods in the Tiber River Basin (central Italy)

 The definition of landslide warning thresholds, based on the analysis of hydrological data, is proposed. In the Tiber River Basin of central Italy historical information on landslides and floods, for the period 1918–1990, was available from a nationwide bibliographical and archive inventory on geohydrological catastrophes. Hydrological data were obtained from mean daily discharge records at various gauging stations within the basin. Several hundred hydrological events, broadly defined as a series of consecutive days having mean daily discharge exceeding a predefined value, were identified. Hydrological parameters obtained from the discharge records were used to rank the events according to their probability to trigger mass movements or inundations and to define regional thresholds for the occurrence of landslides and floods. The proposed approach, not lacking limitations, has conceptual and operational advantages, among which is the possibility of using historical information on geohydrological catastrophes. Received: 20 November 1996 · Accepted: 25 June 1997     

Susceptibility zoning of geological disasters based on GIS: A case of Huining area in Gansu Province

Huining County is located in the central part of Gansu Province, and the geological disasters are extremely developed in this area. There are 16 collapses, 12 landslides and 7 mudslides, which have caused great economic loss. In order to divide and evaluate the susceptibility zoning of geological disasters in Huining County, the authors established the geological disaster database based on the regional geological disaster investigations. The evaluation model of geological disaster susceptibility analysis was established by the analytic hierarchy process and statistical method of GIS spatial analysis, and 14 basic indicator layers were selected. The evaluation units were overlaid, analyzed and verified, and the results show that the geological disaster susceptibility in Huining County can be divided into three zones of high easy-happening area, medium easy-happening area and low easy-happening area. It is considered that the evaluation results are in good agreement with the actual situation of geological disasters, with the expert evaluation method to examine the geological disaster susceptibility results. The evaluation results can provide some reference for the comprehensive prevention and treatment of geological disasters in Huining County.     

基于GIS的地质灾害易发性分区评价——以甘肃省会宁县为例

会宁县地处甘肃省中部,地质灾害极为发育,共发育有崩塌16处、滑坡12处、泥石流7条,地质灾害已对研究区造成了重大经济损失。为了对会宁县地质灾害易发性进行分区评价及指导防灾减灾,在区域地质灾害调查的基础上,建立了地质灾害数据库,采用层次分析法和GIS空间分析统计方法,选取14个基础指标,建立了会宁县地质灾害易发性分析评价模型,对评价单元叠加分析计算及验证分析,将会宁县地质灾害的易发程度划分为3个区,即高易发区、中易发区和低易发区。通过专家评审法检验地质灾害易发性评价结果,认为评价结果与实际地质灾害情况相符性较好,可以为制定会宁县地质灾害综合防治措施提供依据。     

The role of hydrogeology in solution-subsidence development and its environmental impacts; a case-study for Sazlıca (Niğde, Turkey)

Solution-subsidence and other types of collapse failures developed in the vicinity of Sazlıca have been a major source of environmental problems such as groundwater pollution, soil erosion, and foundation failures. Extensive pumping of water from the Lake Dipsiz during irrigation seasons creates landslide developments at the shores of the lake. Five stages of landslide development were observed in the unconsolidated soils around Lake Dipsiz. Bowl-shaped solution-subsidence features with depths from 1 to 3 m and diameters between 1 and 60 m were formed due to excess pumping, and recharge and discharge features of unconfined aquifer. The pumping activities must be controlled to prevent further environmental problems. Lake Dipsiz and other subsidence developments are the groundwater exposure areas highly vulnerable to contamination. The proposed remedies for overcoming the environmental problems are the establishment of conservation areas around such natural features; ceasing the removal of top soil, controlling the urbanization, and keeping the livestock farming away from the areas susceptible to pollution. Received: 2 June 1997 · Accepted: 16 January 1998     

Landslide susceptibility mapping: A comparison of logistic regression and neural networks methods in a medium scale study, Hendek region (Turkey)

Landslide susceptibility mapping is one of the most critical issues in Turkey. At present, geotechnical models appear to be useful only in areas of limited extent, because it is difficult to collect geotechnical data with appropriate resolution over larger regions. In addition, many of the physical variables that are necessary for running these models are not usually available, and their acquisition is often very costly. Conversely, statistical approaches are currently pursued to assess landslide hazard over large regions. However, these approaches cannot effectively model complicated landslide hazard problems, since there is a non-linear relationship between nature-based problems and their triggering factors. Most of the statistical methods are distribution-based and cannot handle multisource data that are commonly collected from nature. In this respect, logistic regression and neural networks provide the potential to overcome drawbacks and to satisfy more rigorous landslide susceptibility mapping requirements. In the Hendek region of Turkey, a segment of natural gas pipeline was damaged due to landslide. Re-routing of the pipeline is planned but it requires preparation of landslide susceptibility map. For this purpose, logistic regression analysis and neural networks are applied to prepare landslide susceptibility map of the problematic segment of the pipeline. At the end, comparative analysis is conducted on the strengths and weaknesses of both techniques. Based on the higher percentages of landslide bodies predicted in very high and high landslide susceptibility zones, and compatibility between field observations and the important factors obtained in the analyses, the result found by neural network is more realistic.     

基于层次分析-模糊综合评价法的徐州市岩溶塌陷易发性评价

为定量评价城市岩溶塌陷灾害,在详细分析徐州市地质条件的基础上,选取了岩溶发育程度、覆盖层条件、水动力条件等8个致灾因子,运用层析分析-模糊综合评价法对研究区岩溶塌陷易发程度进行评价,得到徐州市岩溶塌陷易发程度分区图。研究结果表明：徐州市岩溶塌陷易发程度分为高易发、中易发、低易发、不易发共4个等级。高易发区主要位于市区溶剂厂-新生街一带及张集水源地邓楼水厂-梁堂水厂一带。区内岩溶水水位长期在基岩面附近波动是诱发岩溶塌陷的主要因素,因此在岩溶塌陷高易发区内应加强对岩溶地下水的开采控制,建立岩溶塌陷监测预警系统,预防岩溶塌陷的发生。     

Physically based modelling of shallow landslide sediment yield at a catchment scale

 A shallow landslide erosion and sediment yield component, applicable at the basin scale, has been incorporated into the physically based, spatially distributed, hydrological and sediment transport modelling system, SHETRAN. The component determines when and where landslides occur in a basin in response to time-varying rainfall and snowmelt, the volume of material eroded and released for onward transport, and the impact on basin sediment yield. Derived relationships are used to link the SHETRAN grid resolution (up to 1 km), at which the basin hydrology and final sediment yield is modelled, to a subgrid resolution (typically around 10–100 m) at which landslide occurrence and erosion is modelled. The subgrid discretization, landslide susceptibility and potential landslide impact are determined in advance using a geographic information system (GIS), with SHETRAN then providing information on temporal variation in the factors controlling landsliding. The ability to simulate landslide sediment yield is demonstrated by a hypothetical application based on a catchment in Scotland. Received: 30 October 1996 · Accepted: 25 June 1997     

Field variability of landslide model parameters

 A data set of parameters (slope, soil depth and soil shear strength) relevant to spatially distributed modelling of shallow landslides triggered by rain and snowmelt events was determined from field measurements in 250 grid elements of dimensions 25 m (downslope)×10 m (across slope) in an area of 250 m×250 m on a hillslope in Scotland. These data provide an unusually detailed basis for the evaluation of spatial variability and uncertainty in model parameterisation. The variations in slope and soil strength are represented adequately by normal distributions; a Weibull distribution is suggested for the soil depth data. The factor of safety calculated at each point in the grid was shown partially to identify observed landslides, with a number of false predictions of occurrence. Trend analysis and semivariogram analysis of the data set suggest that the use of kriging could improve upon this approach to landslide prediction by providing areal estimates of parameters at the grid element scale with associated error bounds. Received: 30 October 1996 · Accepted: 25 June 1997     

Hydrogeological and geotechnical assessments of the Kadifekale landslide area, İzmir, Turkey

 The study area is located in the south of İzmir city centre in an area built without planning permission or any overall city plan. In this area, a number of mass movements occurred in the past and the region is still an active landslide field at present. The real sliding factor is geological structure, which is made up of hard volcanic rocks overlying soft Neogene clayey soils, and forms a typical structure prone to sliding. Unplanned human activities change the hydrogeological and geotechnical stabilities of the geological formations in a negative way. Rain and water leaking either directly from the mains or septic holes infiltrate into the ground and act as one of the factors in causing landslides. It is clearly shown that the irregular urbanization in and around Kadifekale is one of the factors contributing to the landslides in the area. To prevent the occurrence of landslides in the study area an effective surface and under ground drainage should be established. Rain and wastewater should be removed from the area by separate systems. Slopes should be reduced, water-loving trees should be planted and construction of high rise buildings should be avoided. Received: 12 December 1997 · Accepted: 4 April 2000     

Chromium and manganese zoning in pelitic garnet and kyanite: Spiral,overprint, and oscillatory (?) zoning patterns and the role of growth rate

X‐ray composition maps and quantitative analyses for Mn, Ca and Cr have been made for six pelitic and calc‐pelitic garnet crystals and Al, Fe and Cr analyses maps have been made for two kyanite crystals, from lower and mid/upper amphibolite facies rocks from the Grenville Province of western Labrador, using an electron microprobe analyser and a laser ablation ICP‐MS. Garnet with spiral (‘snowball’) internal fabrics (S_i) has spiral zoning in major elements, implying that growth was concentrated in discrete regions of the crystal at any one time (spiral zoning). Cr zoning is parallel to S_i in low amphibolite facies garnet with both straight and spiral internal fabrics, indicating that the garnet overprinted a fabric defined by Cr‐rich (mica±chlorite±epidote) and Cr‐poor (quartz±plagioclase) layers during growth (overprint zoning) and that Cr was effectively immobile. In contrast, in mid/upper amphibolite facies garnet porphyroblasts lacking S_i, Cr zoning is concentric, implying that Cr diffusion occurred. Cr zoning in kyanite porphyroblasts appears superficially similar to oscillatory zoning, with up to three or four annuli of Cr enrichment and/or depletion present in a single grain. However, the variable width, continuity, Cr concentration and local bifurcation of individual annuli suggest that an origin by overprint zoning may be more likely. The results of this study explain previously observed nonsystematic Cr zoning in garnet and irregular partitioning of Cr between coexisting metamorphic mineral pairs. In addition, this study points to the important role of crystal growth rate in determining the presence or absence of inclusions and the type of zoning exhibited by both major and trace elements. During fast growth, inclusions are preferentially incorporated into the growing porphyroblast and slow diffusing elements such as Cr are effectively immobile, whereas during slow growth, inclusions are not generally included in the porphyroblast and Cr zoning is concentric.