Abstract
This study aims to assess the localization and size distribution of landslides using automatic remote sensing techniques in (semi-) arid, non-vegetated, mountainous environments. The study area is located in the Kurdistan region (NE Iraq), within the Zagros orogenic belt, which is characterized by the High Folded Zone (HFZ), the Imbricated Zone and the Zagros Suture Zone (ZSZ). The available reference inventory includes 3,190 landslides mapped from sixty QuickBird scenes using manual delineation. The landslide types involve rock falls, translational slides and slumps, which occurred in different lithological units. Two hundred and ninety of these landslides lie within the ZSZ, representing a cumulated surface of 32 km2. The HFZ implicates 2,900 landslides with an overall coverage of about 26 km2. We first analyzed cumulative landslide number-size distributions using the inventory map. We then proposed a very simple and robust algorithm for automatic landslide extraction using specific band ratios selected upon the spectral signatures of bare surfaces as well as posteriori slope and the normalized difference vegetation index (NDVI) thresholds. The index is based on the contrast between landslides and their background, whereas the landslides have high reflections in the green and red bands. We applied the slope threshold map to remove low slope areas, which have high reflectance in red and green bands. The algorithm was able to detect ~96% of the recent landslides known from the reference inventory on a test site. The cumulative landslide number-size distribution of automatically extracted landslide is very similar to the one based on visual mapping. The automatic extraction is therefore adapted for the quantitative analysis of landslides and thus can contribute to the assessment of hazards in similar regions.
Highlights
Landslides are geological phenomena, which include a wide range of ground movements, such as rock falls, deep slope failures and shallow debris flows
We explore the potential of very high spatial resolution data and a semi-deterministic spectral characterization of scars in order to increase the efficiency of automatic extraction
3,190 landslides were derived using visual interpretation (Figure 3); 290 of them were in the Zagros Suture Zone (ZSZ) and
Summary
Landslides are geological phenomena, which include a wide range of ground movements, such as rock falls, deep slope failures and shallow debris flows. These mass movements can happen in offshore, coastal and onshore environments. Guzzetti et al [2] considered that any mass movement is part of a landslide inventory map. These maps show the spatial distribution of deposition and erosion areas produced by gravity-induced mass wasting which may vary in type, age and activity. The accuracy of automatic procedures has increased steadily and they are more and more adequate to be used to generate landslide inventory maps
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