Analysis of a landslide multi-date inventory in a complex mountain landscape: the Ubaye valley case study

R Schlögel,A Remaître,C Doubre,P Reichenbach,J.-P Malet

doi:10.5194/nhess-15-2369-2015

Abstract

Abstract. In the paper we analyse a multi-date landslide inventory prepared for a mountainous area affected by several landslide types with different degrees of activity, we attempt to quantify the uncertainties associated to the mapping, we measure the evolution of morphological indicators and estimate landslide activity and temporal occurrence. The inventory, covering the period 1956–2010, is prepared for the middle section of the Ubaye valley (southern French Alps) based on the analysis of multi-source documents (geomorphological maps, historical reports of landslide events, field surveys, orthophotographs and SAR (synthetic aperture radar) satellite images). The uncertainties derived from the expert interpretation of different sources of information, the landslide morphological features and the affected land covers are taken into account in relation to the source documents. Morphological indicators are calculated to describe quantitatively the evolution of the landslides (length, area, relative elevation, runout distance). Frequency–area density functions are computed to estimate the changes in the landslide distributions and a Poisson model is used to estimate the probability of reactivation of the observed landslides and the occurrence of new failures. The proposed multi-date inventory and the associated statistics provide additional information to the event catalogue managed by the local policy makers.

Highlights

Landslide inventory maps are important documents to describe mass movement spatial distribution in a region and to prepare susceptibility, hazard and risk maps (Guzzetti et al, 2012)
In the paper we analyse a multi-date landslide inventory prepared for a mountainous area affected by several landslide types with different degrees of activity, we attempt to quantify the uncertainties associated to the mapping, we measure the evolution of morphological indicators and estimate landslide activity and temporal occurrence
The uncertainties derived from the expert interpretation of different sources of information, the landslide morphological features and the affected land covers are taken into account in relation to the source documents

Summary

Introduction

Landslide inventory maps are important documents to describe mass movement spatial distribution in a region and to prepare susceptibility, hazard and risk maps (Guzzetti et al, 2012). Geomorphological landslide inventories, classified as historical, event, seasonal or multi-temporal inventories cluster different information: the movement type, the estimated age, the degree of activity, the depth, and the velocity (Guzzetti et al, 2012). Geomorphological features, such as fissures, grabens, ponds, vegetation removal and other morphological changes, may provide information on landslide activity. The event-based or multi-date landslide inventories preparation is hindered by uncertainties linked to the specificity of the source documents (scale, spatial resolution, time period), the type and size of the landslides as well as by the skills of the Published by Copernicus Publications on behalf of the European Geosciences Union

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