Showing papers by "C.J. van Westen published in 2008"

Pore Water Pressure as a Trigger of Shallow Landslides in the Western Ghats of Kerala, India: Some Preliminary Observations from an Experimental Catchment

Abstract: The Western Ghats mountain chain of Kerala, India, is prone to landslides mainly caused by anthropogenic disturbances and very high rainfall amounts. Here, some initial observations on the apparent relationship among pore water pressure fluctuations, rainfall characteristics, and landslide initiation are presented based on monitoring in an experimental catchment in the upper Tikovil River basin. On June 21 and 22, 2007, continuous rain fell for over 10 hours with a total precipitation of 147 mm, causing three shallow landslides in the catchment. Measurements using piezometers in three hollows of the catchment indicate that the rain spell resulted in the development of high pore water pressure from the beginning of the storm that persisted through the time of occurrence of shallow landslides. The pore water pressure patterns in these monitored hollows are possible representatives of the pore water pressure pattern in the hollows where the landslides initiated. This similarity of response pattern enables su...

RiskCity : a training package on the use of GIS for urban multi - hazard risk assessment

Abstract: As part of the capacity building activities of the United Nations University – ITC School on Disaster Geo-Information Management (UNU-ITC DGIM) the International Institute for Geoinformation Science and Earth Observation (ITC) has developed a training package on the application of GIS for multi-hazard risk assessment. The package, called RiskCity comprises a complete suite of exercise descriptions, together with GIS data and presentation materials on the various steps required to collect and analyze relevant spatial data for hazard, vulnerability and risk assessment in an urban environment. The exercises deal with four different types of hazards: earthquakes, flooding, technological hazards, and landslides. The exercises deal with a hypothetical case study, hence the name RiskCity. Most of the data was derived from the city of Tegucigalpa in Honduras, but has been adapted to make the exercises more didactical. They aim to give an understanding of the basic concepts involved in risk assessment, and allow the students to have an idea on how GIS can be used for analyzing the different types of hazards, creating an elements at risk database, assessing vulnerability, making loss estimations using qualitative and quantitative methods, carry out a cost benefit analysis, and use the data for urban planning and disaster risk management. The package has been developed in collaboration with several partner organizations in different continents, and is used as the basis for a series of courses. Currently it is developed into a distance education course.

Seismic vulnerability and capacity assessment: a case study of Lalitpur Sub - Metropolitan City, Nepal

Abstract: This is an effort to identify an appropriate method for assessment of seismic vulnerability and capacity to cope with earthquake disasters, which can be easily adopted by municipal authorities. It includes estimation of building collapse probability and casualties due to different scenario earthquakes, and measuring the capacity of local people to cope with the earthquake disaster in Lalitpur Sub-Metropolitan City (LSMC), Nepal. Building damage and collapse probabilities are estimated for individual buildings considering their conditions in addition to height, construction types and earthquake intensity using an existing damage matrix. Using an empirical relation between building collapse probability and population distribution, established by HAZUS, casualties are estimated for different earthquakes in different time of the day. The level of public awareness, preparedness and capacity are analyzed from the information received by interviewing local people.

High resolution DEM from Cartosat - 1 for landslide investigation in the Himalayan region, India : powerpoint

Abstract: Digital Elevation Models (DEMs) are one of the most critical requirements for landslide investigation. Morphometric parameters extracted from high resolution DEMs are essential for the preparation of landslide susceptibility and risk maps. 2.5m alongtrack panchromatic stereoscopic data from the recently launched Cartosat-1 provide an excellent opportunity for the generation of such DEMs. Through block triangulation with 8 control points and the Rational Polynomial Coefficients (RPC) supplied with the satellite data, a 10 m grid spacing DEM with a total horizontal and vertical RMSE of 1.3 and 1.4 pixel, respectively, was achieved in the very steep topographic areas in the High Himalayan region, characterised by an elevation range of 700 3880m. Given the steep terrain and consequent rapid slope changes, as well as shadow, snow and vegetation cover, fully automated production of high quality elevation models is not feasible. We thus tested the utility of manual break lines to correct spurious points, but also methods to quantify the elevation contribution of vegetation as a means to move towards a digital terrain model (DTM) from a digital surface model (DSM). The corrected surfaces were also used to calculate the volume of the 2007 Salna landslide. Knowledge of failure volumes is a critical component of landslide hazard assessment as well as for runout modelling, and Cartosat data appear suitable for accurate volume calculation of large failures.

Use of historic landslide inventories for hazard assessment along communication routes : poster

Abstract: Communication routes such as railways or roads in hilly terrain are often prone to slope failure and in due course of time they often retrograde into landslides of larger dimension. Quantitative landslide risk assessment along such corridors requires detailed information on the temporal and spatial probability of slope failures. Such information is normally very difficult to collect, unless historic data on road blockage can be collected from the road maintenance department.

Seismic loss estimation for Lalitpur, Nepal

Abstract: The main objective of the research project, entitled “Strengthening local authorities in risk management” is to develop spatial information systems for municipalities, which will allow local authorities to evaluate the risk of natural disasters in their municipality, in order to implement strategies for vulnerability reduction. The project concentrates on medium-sized cities in developing countries, which do not yet utilize Geographic Information Systems in their urban planning, and which are threatened by natural hazards. The methodology concentrates on the application of methods for hazard assessment, elements at risk mapping, vulnerability assessment, risk assessment, and the development of GIS-based risk scenarios for varying hazard scenarios and vulnerability reduction options, using structural and/or non-structural measures. In the development of elements at risk databases use is made of interpretation of high-resolution satellite imagery, combined with extensive field data collection, using mobile GIS. Here results are presented on earthquake loss estimation for the city of Lalitpur in Nepal, for buildings and for population losses.