Analytical ‘decisiveness’ as a robust measure of the absolute importance of landslide predisposing factors

Although some methods have been proposed to measure the absolute importance of landslide predisposing factors, they are unfortunately complicated by inherent difficulties. In this study, a robust analytical index – ‘decisiveness,’ is proposed for measuring factor absolute importance. The idea is to evaluate factor importance according to the capability of differentiating landslide-susceptible and landslide-insusceptible areas; that is, those factors that can zone the target area into units either highly favorable or highly unfavorable to landslides will be of high importance for landslides. For a specific factor, the favorability values of all grid cell units in the target area are first calculated using the certainty factor method. Then, the magnitudes of all those favorability values are integrated to constitute the decisiveness index. The decisiveness ranges within [0, 1], with higher values indicating greater importance. Updated versions of the open software ALSA can be used to calculate favorability values and further decisiveness. The significance and robustness of decisiveness were validated in a case study. Although decisiveness has been proposed to measure the factor importance for landslides, the novel idea and index can also be used to evaluate the importance of factors in determining the spatial distribution of other objects or phenomena.