Challenges in analyzing landslide risk dynamics for risk reduction planning

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Abstract

This paper discusses approaches to evaluate how landslide risk might change over time. Multi-hazard risk assessment (MHRA) is the quantitative estimation of the spatial distributions of potential losses for an area, of multiple natural hazards with different hazard interactions, with multiple event probabilities, for multiple types of elements-at-risks, and multiple potential loss components. The paper first discusses the various types of hazard interactions in which landslides are involved. An example is presented of a MHRA at district level in Tajikistan for a combination of seven hazard types (earthquakes, floods, windstorms, drought , landslides , mudflows and snow avalanches ) and five types of elements-at-risk (Built-up area, buildings, people, agriculture and roads). After discussing problems involved in such types of static MHRA projects, the paper continues with describing the need for analyzing changing multi-hazard risk as a basis for decision-making. These changes may be related to changes in triggering or conditional factors, increasing exposure of elements-at-risk, and their vulnerability and capacity. Dynamic risk can be evaluated on the long term because of changes in climate, land use, population density, economy, or social conditions. Climate change scenarios still contain large uncertainties in the changes in return periods of extreme rainfall events, and their spatial variation in mountainous areas. In addition, feedback mechanisms between climate change and land use change play an important role, but are difficult to incorporate in the risk assessment. Changes in landslide risk might also be occurring in a short time frame, and assessed as a basis for impact based forecasting, and to analyze the consequences of hazard interactions after major events, for instance after the occurrence of wildfires, major earthquakes, volcanic eruptions, or extreme rainfall events, which alter the conditional factors for the occurrence of landslides. An overview is given of the tools available for multi-hazard assessment, stressing the importance for developing integrated physically based multi-hazard models. One of such models, OpenLISEM Hazard, is presented in some more detail. In addition, an overview is given of the tools for multi-hazard risk assessment, stressing the need to incorporate landslide risk within the existing models, as currently this is not taken into account at a sufficient level. One example is given of a Spatial Decision Support System for dynamic multi-hazard analysis, which aims to assist stakeholders in decision making of optimal risk reduction alternatives under various future scenarios. This is further illustrated with a case study for the city of Envigado, near Medellin in Colombia. The OpenLISEM Hazard model is used to generate hazard scenarios for flood, landslides, and debris flows for different return periods of triggering rainfall. Building footprints are updated and classified into occupational types, and structural types, and absolute vulnerability curves were generated. Current multi-hazard risk is analyzed. After that several future scenarios of climate change and population change are outlined, for which the changing risk is analyzed. Finally, three alternatives for risk reduction are presented, their risk reduction is calculated, and eventually the optimally performing alternative under different future scenarios is selected.
Original languageEnglish
Pages1-30
Number of pages30
Publication statusPublished - 22 Feb 2021
Event13th International symposium on landslides - , Colombia
Duration: 22 Feb 202126 Feb 2021
Conference number: 13

Conference

Conference13th International symposium on landslides
CountryColombia
Period22/02/2126/02/21

Keywords

  • Landslide risk assessment
  • Multi-hazard risk
  • Risk reduction

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