Showing papers by "C.J. van Westen published in 2009"

Parameterizing a physically based shallow landslide model in a data poor region

Abstract: Shallow landslides and consequent debris flows are an increasing concern in the Western Ghats of Kerala, India. Their increased frequency has been associated with deforestation and unfavourable land-use practices in cultivated areas. In order to evaluate the influence of vegetation on shallow slope failures a physically based, dynamic and distributed hydrological model (STARWARS) coupled with a probabilistic slope stability model (PROBSTAB) was applied to the upper Tikovil River basin (55·6 km2). It was tuned with the limited evidence of groundwater conditions during the monsoon season of 2005 and validated against observed landslide activity in the hydrological year 2001–2002. Given the data poor conditions in the region some modifications to the original model were in order, including the estimation of parameters on the basis of generalized information from secondary sources, pedo-transfer functions, empirical equations and satellite remote sensing data. Despite the poor input, the model captured the general temporal and spatial pattern of instability in the area. Sensitivity analysis proved root cohesion, soil depth and angle of internal friction as the most dominant parameters influencing slope stability. The results indicate the importance of root cohesion in maintaining stability and the critical role of the management of rubber plantations in this. Interception and evapotranspiration showed little influence on the development of failure conditions. The study also highlights the importance of high resolution digital terrain models for the accurate mechanistic prediction of shallow landslide initiation. Copyright © 2009 John Wiley & Sons, Ltd.

A Quantitative Approach for Improving the BIS (Indian) Method of Medium-Scale Landslide Susceptibility

Abstract: In India, the Bureau of Indian Standards (BIS) recommends a heuristic method for medium-scale (1:25,000/1:50,000) landslide susceptibility mapping. This is based on fixed ratings of geofactors, without the inclusion of landslide inventory information. In BIS method, the pre-defined ratings of geofactors are applied over diverse areas, irrespective of the terrain-specific spatial inter-dependence of geofactors and landslide types, which leads to rather moderate prediction. In this paper, we evaluate the effectiveness of the existing BIS method in Darjeeling Himalaya through a quantitative method adapting weights of evidence (WofE) modeling. The quantified spatial associations between specific geofactors for different landslide types and failure mechanisms that were generated, using this method showed improved prediction rates as compared to the BIS method of fixed ratings of geofactors. We therefore recommend adjusting the existing BIS guidelines by inclusions of weights, derived locally through quantitative spatial analysis of landslide inventories and geofactor maps.

Rainfall - based temporal probability for landslide initiation along transportation routes in Southern India

Abstract: We present a temporal probability model for the initiation of shallow translational debris slides along cut slopes of a railroad sector in southern India, for which an extensive landslide database was available, covering a time span of 15 years. The model is based on rainfall thresholds and gives the likelihood of occurrence of rainfall that can trigger landslides with a certain density. Rainfall thresholds were established based on the relationship of daily and antecedent rainfall. The temporal probability was calculated as the joint probability of annual exceedance probability of the rainfall threshold, determined using a Poisson probability model and the probability of landslide occurrence once the threshold had been exceeded. The model was tested for a 19 kilometer long railroad alignment in the Nilgiri hills of southern India. The annual probability varies from 0.27 to 0.49. The result of the model was extended to the nearby roadroute, which had similar geo-environmental condition. More than 60% of the recorded landslides along the road occurred where temporal probability was high (> 0.40). The temporal probability derived from the model forms the basis for future landslide hazard analysis along the transportation routes.

Utilization of airborne LIDAR data for landslide mapping in forested terrain : status and challenges

Abstract: With the advancement in sensor technology and point clouds processing algorithms, the capability of Airborne LIDAR data for landslide mapping in forested terrain is much promising. Most of the available air-based platform products either from an aerial-photograph, satellite imagery or synthetic aperture radar are not appropriate for interpretation of landslide features which are covered by dense vegetation. Mapping the landslides in such environment requires additional information that can help the interpreters to recognise landslide characteristics and later on be used to distinguish landslide activities. In this research, we present the status and challenges of utilizing the high-resolution airborne LIDAR data for landslide mapping in forested terrain. European dataset in Barcelonnette, Southern French Alps has been used. Amongst the important issues in this research is bare earth extraction. In order to preserve the important geomorphological feature, bare earth extraction based on hierarchical robust filtering is presented with a suitable filter parameterization. Finally, high-resolution Digital Terrain Model (DTM) is used to calculate the local topography roughness and characterize the landslide morphology.

Modelling the runout of a debris flow of the Western Ghats, Kerala, India

Abstract: (1) Department of Earth Systems Analysis, International Institute for Geoinformation Science and Earth Observation (ITC), Enschede, Netherlands (lukose11753@itc.nl, quanluna@itc.nl, westen@itc.nl / Ph: +31534874336), (2) 2. Estacion Experimental de Aula Dei Consejo Superior de Investigaciones Cientificas (CSIC), (Aula Dei Experimental Station Spanish National Research Council), Avda. Montanana 1005; 50059 Zaragoza, Spain (sbegueria@eead.csic.es / Ph: +34 976 716107)

Debris flow susceptibility assessment on medium scale using official and recently mapped inventories

Abstract: (1) Department of Environmental and Territorial Sciences, University of Milano-Bicocca, (DISAT-UNIMIB) Piazza della Scienza 1, 20126 Milan, Italy, (2) Institute for the Dynamic Environmental Processes, National Research Council (CNR-IDPA), Piazza della Scienza 1, 20126 Milan, Italy, (3) International Institute for Geoinformation Science and Earth Observation (ITC), ITC, P.O. Box 6, 7500 AA Enschede, The Netherlands.

Distance education course on spatial multi-hazard risk assessment, using Open Source software

Abstract: As part of the capacity building activities of the United Nations University ‐ ITC School on Disaster GeoInformation Management (UNU-ITC DGIM) the International Institute for Geoinformation Science and Earth Observation (ITC) has developed a distance education course on the application of Geographic Information Systems for multi-hazard risk assessment. This course is designed for academic staff, as well as for professionals working in (non-) governmental organizations where knowledge of disaster risk management is essential. The course guides the participants through the entire process of risk assessment, on the basis of a case study of a city exposed to multiple hazards, in a developing country. The courses consists of eight modules, each with a guide book explaining the theoretical background, and guiding the participants through spatial data requirements for risk assessment, hazard assessment procedures, generation of elements at risk databases, vulnerability assessment, qualitative and quantitative risk assessment methods, risk evaluation and risk reduction. Linked to the theory is a large set of exercises, with exercise descriptions, answer sheets, demos and GIS data. The exercises deal with four different types of hazards: earthquakes, flooding, technological hazards, and landslides. One important consideration in designing the course is that people from developing countries should not be restricted in using it due to financial burdens for software acquisition. Therefore the aim was to use Open Source software as a basis. The GIS exercises are written for the ILWIS software. All exercises have also been integrated into a WebGIS, using the Open source software CartoWeb (based on GNU License). It is modular and customizable thanks to its objectoriented architecture and based on a hierarchical structure (to manage and organize every package of information of every step required in risk assessment). Different switches for every component of the risk assessment course have been defined and through various menus the user can define the options for every exercise. For every layer of information tools for querying, printing, searching and surface analysis are implemented, allowing the option to compare maps at different scale and for on-line interpretations.

Hazard and potential damage evaluation in a web - GIS as support for risk management : abstract

Abstract: (1) Department of Earth Systems Analysis (ESA), International Institute for Geo-Information Science and Earth Observation, Hengelosestraat 99 P.O. Box 6 7500 AA Enschede The Netherlands, (2) Department of Environmental Sciences, University of Milan-Bicocca, Piazza della Scienza 1, 20126 Milan, Italy, (3) Institute for the Dynamic of Environmental Processes, National Research Council (CNR-IDPA), Piazza della Scienza 1, 20126 Milan, Italy

Landslide hazard and risk assessment along a transportation corridor in India

Abstract: Landslide hazard and risk assessment is a complicated process which requires a large amount of data. One of the most essential data types consists of historical landslide information. This paper presents a quantitative approach for landslide risk assessment for a road and a railway alignment in parts of Nilgiri hills in southern India. The method allows estimating direct risk affecting the alignments, vehicles and people. The method uses three basic parameters to quantify direct risk: hazard, vulnerability and value of exposed elements. Hazard in a given return period is expressed as the number of landslides of a given magnitude per kilometer per annum obtained using Gumbel distribution and magnitude-frequency statistics. A total of 1040 landslides were collected from historical records, of which 95.5% occurred in cut slopes along the railway and road alignment. All landslides were grouped in different magnitude classes. In total 18 hazard scenarios were generated using three magnitude classes (class I to III) and six return periods (1, 3, 5, 15, 25 and 50 years). The assessment of vulnerability of the alignment was based on the damage records, combined with expert opinion. Direct specific losses for the alignment (railway line and road), vehicle (bus, lorry, car and motorbike) and train were expressed in monetary values, and direct specific loss of life of commuters was expressed in annual probability. The detailed estimation of direct risk will facilitate to develop landslide risk mitigation and management strategies for transportation lines in the study area.