Abstract
Abstract. For a 277 km2 study area in the Flemish Ardennes, Belgium, a landslide inventory and two landslide susceptibility zonations were combined to obtain an optimal landslide susceptibility assessment, in five classes. For the experiment, a regional landslide inventory, a 10 m × 10 m digital representation of topography, and lithological and soil hydrological information obtained from 1:50 000 scale maps, were exploited. In the study area, the regional inventory shows 192 landslides of the slide type, including 158 slope failures occurred before 1992 (model calibration set), and 34 failures occurred after 1992 (model validation set). The study area was partitioned in 2.78×106 grid cells and in 1927 topographic units. The latter are hydro-morphological units obtained by subdividing slope units based on terrain gradient. Independent models were prepared for the two terrain subdivisions using discriminant analysis. For grid cells, a single pixel was identified as representative of the landslide depletion area, and geo-environmental information for the pixel was obtained from the thematic maps. The landslide and geo-environmental information was used to model the propensity of the terrain to host landslide source areas. For topographic units, morphologic and hydrologic information and the proportion of lithologic and soil hydrological types in each unit, were used to evaluate landslide susceptibility, including the depletion and depositional areas. Uncertainty associated with the two susceptibility models was evaluated, and the model performance was tested using the independent landslide validation set. An heuristic procedure was adopted to combine the landslide inventory and the susceptibility zonations. The procedure makes optimal use of the available landslide and susceptibility information, minimizing the limitations inherent in the inventory and the susceptibility maps. For the established susceptibility classes, regulations to link terrain domains to appropriate land rules are proposed.
Highlights
Understanding the role of individual factors controlling landslide location, geographical pattern, and spatial density is important to predict where landslides can occur in the future, i.e. to ascertain landslide susceptibility (Varnes and IAEG, 1984; Soeters and van Westen, 1996; Guzzetti et al, 1999, 2005; Van Den Eeckhaut et al, 2006)
Van Den Eeckhaut et al.: Combined landslide inventory and susceptibility assessment recognize the main causes of instability in the investigated area, (iii) the availability and quality of relevant thematic and environmental data, including maps showing morphological, geological, and land use conditions prone to landslides, (iv) the type of modelling approach adopted for the susceptibility assessment, and (v) the availability of adequate GIS, modelling and statistical software to perform the susceptibility analysis
We describe the two types of mapping units selected for this study: grid cells and topographic units
Summary
Understanding the role of individual factors controlling landslide location, geographical pattern, and spatial density is important to predict where landslides can occur in the future, i.e. to ascertain landslide susceptibility (Varnes and IAEG, 1984; Soeters and van Westen, 1996; Guzzetti et al, 1999, 2005; Van Den Eeckhaut et al, 2006). The main advantages and drawbacks of the different types of mapping units are known (van Westen et al, 1993; Carrara et al, 1995; Guzzetti et al, 1999; Van Den Eeckhaut et al, 2005; Guzzetti, 2006; and references therein), only a few investigators have critically examined the influence of different terrain subdivisions on susceptibility zonation (Carrara et al, 1995, 2008) This is surprising, because selection of different terrain partitioning units can result in considerable differences in the susceptibility assessment (Carrara et al, 2008).
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