Geo-Information tools for Landslide Risk Assessment. An overview of recent developments

The aim of this contribution is to give an overview of recent developments in the use of Geographical Information Systems and Earth Observation which have been applied for improved landslide inventory mapping, landslide susceptibility and hazard assessment, elements at risk mapping, and finally landslide vulnerability and risk assessment. Geo-Information science and earth observation consists of a combination of tools and methods for the collection through aerospace survey techniques -, storage and processing of geospatial data, for the dissemination and use of these data and of services based on these data. New relevant advances in this field are discussed, such as the wider availability and higher accuracy of Digital Elevation Models (e.g. from ASTER, SRTM, Lidar) and the improved spatial and spectral resolution of satellite images. Another important development is in the field of digital data collection through digital stereo image interpretation, and the use of mobile GIS for data collection of landslides and elements at risk. Finally an overview is given of the use of GIS in landslide hazard, vulnerability and risk assessment. regulatory activities to emergency management (Fedra, 1998). Modern information technology provides some of the tools to support these activities, leading to the development of risk information systems that can be used for both analyzing risk and evaluating the consequences of decisions that have to be taken to mitigate or reduce risk at both short term (emergency planning) and long term (development planning). The aim of this paper is to give an overview of recent developments in the use of Geographical Information Systems and Earth Observation which have been applied for improved landslide inventory mapping, landslide susceptibility and hazard assessment, elements at risk mapping, and finally landslide vulnerability and risk assessment. This paper does not intend to give an overview of the various methods for landslide hazard and risk assessment. For overview publications regarding landslide hazard methods the reader is referred to publications such as Varnes (1984), Soeters and Van Westen (1996), Aleotti and Chowdury (1999) and Guzzetti et al. (1999; 2000). The fairly recent topic of landslide risk assessment is discussed by Einstein (1988), Chowdhury (1988), Fell (1994), Fell and Hartford (1997), Hungr et al. (1999), Hearn and Griffiths (2001) and Dai et al. (2002), collections of publications on risk assessment can be found in Turner and Schuster, (1996), Sennestet, (1996), Cruden and Fell (1997), and McInnes and Jakeways (2002). This paper is partly based on an extensive literature search using a Web-based search engine (Geobase) for scientific journal articles basically from the past 8 years. 2 GEO-INFORMATION SCIENCE AND EARTH OBSERVATION FOR LANDSLIDE HAZARD AND RISK ASSESSMENT Geo-information science and earth observation consist of a combination of tools and methods for the collection, storage and processing of geo-spatial data and for the dissemination and use of these data and of services based on these data. This implies the development and application of concepts for spatial data modeling, for information extraction from measuring and image data, and for the processing, analysis, dissemination, presentation and use of geospatial data. It also implies the development and implementation of concepts for the structuring, organization and management of geo-spatial production processes in an institutional setting. Due to the diversity and large volumes of data needed, and the complexity in the analysis procedures, quantitative landslide risk assessment has only become feasible in the last decade or so, due to the developments in the field of Geo-Information science. When dealing with GIS-based landslide hazard assessment, elements at risk mapping, and vulnerability/risk analysis, experts from a wide range of disciplines, such as earth sciences, hydrology, information technology, urban planning, architecture, civil engineering, economy and social sciences need to be involved. Carrara et al. (1999), in an interesting overview paper on the use of GIS technology for the prediction and monitoring of landslide hazards, indicated some of the negative aspects of the extensive use of GIS in the process, such as: • Computer-generated results are considered to be more objective and accurate than products derived by experts in the conventional way through extensive field mapping; • The use of GIS and the production of less accurate hazard maps by users that are not experts in earth sciences; • The increased focus on the use of new computational techniques for landslide hazard assessment, and less interest on the collection of reliable data; For the average earth scientist it is difficult to keep up with the rapid developments in the field of Geoinformation Science and Earth Observation. The number of new sensors and platforms, and the amount of acronyms is overwhelming. Also the change of GIS software from one version to the next, in which the methods that had been developed earlier on do no longer function, because of changes in file structure or interface, can be frustrating to many earth scientists. Nevertheless, GIS has become an almost compulsory tool in landslide hazard and risk assessment, and it is the challenge to keep on using it as a tool, and not as an objective in itself. When using GIS, the following components of a landslide risk project can be differentiated: data collection, data entry, data management, and data modeling. An overview of the various aspects related to the use of GIS technology in landslide risk assessment is given in Figure 1. In the following section a number of specific aspects will be treated further. 3 COLLECTING, ENTERING AND ORGANIZATION OF DATA FOR LANDSLIDE RISK ANALYSIS. In the field of data collection for landslide hazard, vulnerability and risk assessment, the developments in the fields of Geo-Information Science and Earth Observation have shown a major impact in the fields of DEM generation, digital mapping and mobile GIS. Figure 1: Different components related to the use of Geo-Information tools and methods for risk analy-