A new tree-ring-based index for the expression of spatial landslide activity and the assessment of landslide hazards

Abstract

Dendrogeomorphic methods enable a very accurate reconstruction of spatio-temporal landslide behaviour. Unfortunately, existing approaches of spatial reconstruction suffer from many imperfections (e.g. dependence on tree age or impact of forest management). This study developed, presented, and tested a new approach for the spatial reconstruction of landslide movements based on tree-ring data that eliminates the mentioned problems. The new spatial event-response index (SIt ), developed for GIS, follows the logic of the standard event-response index used for the expression of chronological landslide behaviour and considers the uneven spatial pattern of trees. The main advantage of the new approach is in the consideration of the position of disturbed trees but also of undisturbed ones. This principle prevents over-interpretation of results because it can effectively filter the possible effects of soil creep (nonslide) movements. The approach was tested on three landslides of different types using data from 306 tree-ring series. The results suggest good agreement of the new index with the standard chronological event-response index for all landslide types. This index can be used for hazard assessment of large landslide areas and possibly, if research extended to zones outside of the landslide, even for regional landslide hazard assessment.