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Pré-Publication, Document De Travail Année : 2023

Landslides in French tropical environments: lessons from new inventories to improve geomorphological and hazard knowledge

Yaël Guyomard
  • Fonction : Auteur
Mathieu Mengin
  • Fonction : Auteur
Clara Lévy
Olivier Monge
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  • PersonId : 1128028

Résumé

A large diversity of poorly known and damaging landslides are located in French overseas tropical territories. These mountainous territories present a large variety of heterogeneous, juxtaposed or overlapping, often highly weathered materials (i.e. volcanic, volcano-sedimentary or metamorphic) particularly susceptible to landslides. French overseas territories are often hit by intense weather conditions (cyclones, hurricanes or heavy tropical rains) or earthquakes, which makes them all the more vulnerable to landslides. Each landslide inducing damage is listed in the French national landslide database (BD-MVT). However, it is incomplete because not all are damaging phenomena, especially on undeveloped slopes. Thus, in order to create statistically robust landslide database in these territories, the BD-MVT has been completed by visual remote sensing analyses (aerial photograph and stereoscopic analyses, orthophotographs and Google Earth® imageries investigations, etc.), and historical documents analyses. Each mapped phenomenon is integrated in standardized spatial databases with a series of attributes (i.e. type, materials involved, activity, period of occurrence, etc.). Morphometric attributes (e.g. length, width, reach angle, area, etc.) are derived from the landslide polygons and using local DTMs with a homogeneous resolution for all the studied territories. Every inventory has been verified and completed with field surveys (Table 2). They provide fundamental insights for the understanding concerning the physio-geographical conditions of landslide initiation and runout and help to better understand geomorphological characteristics of each environment. Through a series of statistical indices supplemented by field observations, this presentation aims to show the landslide specificities of each overseas territories and brings insights to understand the variety of processes involved (natural or anthropogenic). Such detailed inventories allow the integration of large- to small-size landslides in a global geomorphological analysis. In particular, moderate to small landslides triggered by cyclonic rainstorms play a significant role in the dismantling processes of mountains edifices (volcanic or others). The first results obtained are promising, and suggest that the comprehensive analysis of overseas landslide inventories, beyond the information they bring for susceptibility and hazard analyses, can provide valuable information for understanding the role of landslides in the landscape evolution of tropical territories.
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Dates et versions

hal-04191998 , version 1 (31-08-2023)

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  • HAL Id : hal-04191998 , version 1

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Yannick Thiery, Claire Rault, Bastien Colas, Mélody Prémaillon, Aude Nachbaur, et al.. Landslides in French tropical environments: lessons from new inventories to improve geomorphological and hazard knowledge. 2023. ⟨hal-04191998⟩

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