Showing papers by "C.J. van Westen published in 2013"

Recommendations for the quantitative analysis of landslide risk

Abstract: This paper presents recommended methodologies for the quantitative analysis of landslide hazard, vulnerability and risk at different spatial scales (site-specific, local, regional and national), as well as for the verification and validation of the results. The methodologies described focus on the evaluation of the probabilities of occurrence of different landslide types with certain characteristics. Methods used to determine the spatial distribution of landslide intensity, the characterisation of the elements at risk, the assessment of the potential degree of damage and the quantification of the vulnerability of the elements at risk, and those used to perform the quantitative risk analysis are also described. The paper is intended for use by scientists and practising engineers, geologists and other landslide experts.

Remote sensing and GIS for natural hazards assessment and disaster risk management

Abstract: The world has experienced an increasing impact of disasters in the past decades. Many regions are exposed to natural hazards, each with unique characteristics. The main causes for this increase can be attributed to a higher frequency of extreme hydro-meteorological events, most probably related to climate change and an increase in a vulnerable population. To reduce disaster losses, more efforts should be applied toward disaster-risk management, with a focus on hazard assessment, elements-at-risk mapping, and vulnerability and risk assessment, all of which have an important spatial component. Multi-hazard assessment involves the assessment of relationships between different hazards, especially concatenated or cascading hazards. The use of Earth observation (EO) products and geographic information systems (GIS) has become an integrated approach in disaster-risk management. Hazard and risk assessments are carried out at multiple scales, ranging from global to community levels. These levels have their own objectives and spatial data requirements for hazard inventories, environmental data, triggering or causal factors, and elements-at-risk. This chapter provides an overview of various forms of spatial data, and examines the approaches used for hazard and risk assessment. Specifically, hazard examples include earthquakes, windstorms, drought, floods, volcanic eruptions, landslides, and forest fires. Several approaches are also treated that have been developed to generate elements-at-risk databases with emphasis on population and building information, as these are the most used categories for loss estimation. Furthermore, vulnerability approaches are discussed, with emphasis on the methods used to define physical vulnerability of buildings and population, and indicator-based approaches used for a holistic approach, also incorporating social, economic, and environmental vulnerability, and capacity. Finally, multi-hazard risk approaches and spatial-risk visualization are addressed. Multi-hazard risk assessment is a complicated procedure, which requires spatial data on many different aspects and a multi-disciplinary approach. Within this procedure, geographers and in particular geomorphologists can play a key role, as they are able to integrate spatial information from various disciplines. The research challenge for geomorphologists is to focus on the integrated modeling of multi-hazards that share the same triggering event or occur as cascading hazards.

Analysis and uncertainty quantification of dynamic run-out model parameters for landslides.

Abstract: The main goals of landslide run-out modeling should be the assessment of future landslide activity with a range of potential scenarios, and the information of the local populations about the hazards in order to enable informed response measures. In recent times, numerical dynamic run-out models have been developed which can assess the velocity and extent of motion of rapid landslides such as debris flows and avalanches, flow slides and rock avalanches. These models are physically-based and solved numerically, simulating the movement of the flow using constitutive laws of fluid mechanics in one or two dimensions. Resistance parameters and release volumes are crucial for a realistic simulation of the landslide behavior, whereas it is generally difficult to measure them directly in the field. Uncertainties in the parameterization of these models yield many uncertainties concerning their frequency values, which must be addressed in a proper risk assessment. Based on the probability density functions of release volumes and friction coefficients of a given landslide model, this work aims to systematically quantify the uncertainties in the run-out modeling. The obtained distributions can be used as an input for a probabilistic methodology where the uncertainties in the release volume and friction coefficients (rheological parameters) inside the dynamic models can be addressed. This will improve the confidence of the dynamic run-out model outputs such as the distribution of deposits in the run-out area, velocities and impact pressures, important components for a risk analysis and regulatory zoning.

Spatial Distribution of Landslide Dams Triggered by the 2008 Wenchuan Earthquake

Abstract: Landslide dams are a common type of river disturbance in tectonically active mountain belts with narrow and steep valleys. Here we present an unprecedented inventory of 828 landslide dams triggered by the 2008 Wenchuan earthquake, China. Of the 828 landslide dams, 501 completely dammed the rivers, while the others only caused partial damming. The spatial distribution of landslide dams was similar to that of the total landslide distribution, with landslide dams being most abundant in the steep watersheds of the hanging wall of the Yingxiu-Beichuan Thrust Fault, and in the northeastern part of the strike-slip fault near Qingchuan. We analyzed the relation between landslide dam distribution and a series of seismic, topographic, geological, and hydrological factors.