Shallow Landslide Susceptibility Mapping for Zagreb Hilly Area, Croatia

Abstract

The aim of this study is to map the landslide susceptibility of the hilly area of Mt. Medvednica located in the northwestern part of the City of Zagreb, Croatia. Landslides in this region are mostly shallow movements of superficial deposits along contacts with fresh deposits of soil and cause significant economic losses by damaging houses and the urban infrastructure. The method used here is the deterministic slope stability analysis model SINMAP which is developed by Pack et al. (A stability index approach to terrain stability hazard mapping. SINMAP user’s manual, 1998; A stability index approach to terrain stability hazard mapping. SINMAP user’s manual, 2005). SINMAP is a raster based slope stability predictive tool based on coupled hydrological-infinite slope stability model. This approach applies to shallow translational landsliding phenomena controlled by shallow ground water convergence. The input data required for this model are (1) inventory of past landslides in a point vector format, (2) Digital Elevation Model (DEM) of the study area, (3) geotechnical data such as soils strength properties, thickness of soil above the failure plane, and (4) hydrological data such as soil hydraulic conductivity and the rainfall. Because the geotechnical data and hydrological data are highly variable in both space and time, the method does not require numerically precise input and accepts ranges of values that represent this uncertainly. The major output of this model is the stability index grid theme, which can be used as a landslide susceptibility map. The results also provided slope area plots and statistical summary for each calibration region in the study area facilitating the data interpretation. The landslide susceptibility map which is developed in this study is also compared with the results from the Analytic Hierarchy Process (AHP) method and aerial photo interpretation.