LANDSLIDE RISK MANAGEMENT IN THE URBAN DEVELOPMENT OF SANDNES (NORWAY)

The research reported focuses on the multi-causal landslide risk in Sandnes (Norway) in connection with the climate change, the use of the land and the geological/geotechnical properties of the urban subsoil. The municipality is giving special focus on the potential climate change challenges in the development plans of the city and the weather is a significant triggering factor of landslides. The average annual precipitation is 1290 mm and the Norwegian Environmental Agency (NEA) estimates a 10 % increase by 2100 and a 40 % increase for the short-term rainfall (3 h). In addition, the NEA expects sea level to rise between 59 and 89. The study includes records of land use, demographic growth (+1.5 % annually), historical maps and aerial imagery. Events occurred in the past have been inventoried by interviews and document retrieval. Additionally, geological, geotechnical and hydrogeological data from surveys performed in the area have been gathered. The data material is georeferenced in a GIS database for visualization and further treatment. We give special attention to the quality and density of the data to account for the uncertainty and lack of information for certain subareas within the geographical boundaries. This will provide guidance for future work such as soil sampling campaigns. A multi-layered model has been created combining the different aspects studied: elevation, slope, hydrology, historical information and geological data. We model the urban area theoretically affected by the sea level rise and the potential effects on different soils. Finally, the work includes preliminary landslide hazard and vulnerability maps of the present urban plot.