The effectiveness of hillshade maps and expert knowledge in mapping old deep-seated landslides

Large differences in the number of presumed landslides and the extent of the hillslopes thought to be affected by landslides were reported among the seven experts. The polygon and pixel efficiency were introduced to estimate the quality of the landslide maps based on hillshade maps and expert knowledge. Compared to the field survey-based landslide inventory, the quality of the landslide inventories based on the hillshade maps and expert knowledge was relatively low. Experts familiar with the study area obtained somewhat better results than experts who visited the study area only once. A combination of the seven expert maps did not result in a good inventory map because too many unaffected hillslopes were incorrectly indicated as affected by landslides. The results obtained in this study are comparable to an investigation carried out by (Wills, C.J., McCrink, T.P., 2002. Comparing landslide inventories, the map depends on the method. Environmental and Engineering Geoscience 8, 279-293). Although the tested method can never replace a detailed field survey, taking into account the proposed improvements, it can be used for the creation of a regional inventory map of old landslides in a densely forested area where light detection and ranging (LIDAR) data are unavailable.