Little Ice Age glacial systems and related natural instability processes in the Orco Valley (North-Western Italy)

Stefania Lucchesi,Stefania Bertotto,Marta Chiarle,Gianfranco Fioraso,Marco Giardino,Guido Nigrelli

doi:10.1080/17445647.2018.1564382

Abstract

ABSTRACT Glaciated and recently (post-Little Ice Age) deglaciated areas are very dynamic environments, undergoing continuous changes, in particular as a consequence of climatic fluctuations and cryosphere changes. The intense geomorphic activity that takes place here conditions natural hazard, sediment transport and tourist fruition. A geo-morphological mapping with applicative purposes has to take into account the peculiarities and the dynamism of these specific areas. We here propose a methodological approach based on the interpretation of a multitemporal set of aerial photos (from 1983 to 2012), in a GIS environment, with application to the sectors modeled by Little Ice Age glaciers in the upper Orco Valley (NW Italy). The result is a geo-morphological map focused on the elements that are most relevant for application purposes, complemented by a map of the spatio-temporal distribution of the natural instability processes identified in the study area for the reference period, aimed to highlight the recent dynamism of the geomorphological elements in the map.

Highlights

Glacial and periglacial areas are very dynamic environments, as a result of the incessant geomorphic activity carried out by glaciers during their advances and retreats, in response to climate fluctuations (Ballantyne, 2002; Giardino, Mortara, & Chiarle, 2017; Martini, Brookfield, & Sadura, 2001; Zasadni, 2007)
Particular attention should be given to areas of recent and very recent deglaciation: here, rocks and deposits have come to light, which were previously buried by ice and not exposed to atmospheric processes and to gravitational instability phenomena (Chiarle, Geertsema, Mortara, & Clague, 2011; Deline, Gardent, Magnin, & Ravanel, 2012; Giardino, Perotti, Bacenetti, & Zamparutti, 2013)
Good multitemporal set of images allowed to (i) overcome local visibility problems caused by shadows, clouds, or snow cover, that can be encountered on a single flight and (ii) assess the dynamism of the geomorphological elements, by identifying the sectors that are recurrently subject to natural instability

Summary

Introduction

Glacial and periglacial areas are very dynamic environments, as a result of the incessant geomorphic activity carried out by glaciers during their advances and retreats, in response to climate fluctuations (Ballantyne, 2002; Giardino, Mortara, & Chiarle, 2017; Martini, Brookfield, & Sadura, 2001; Zasadni, 2007). To be suitable for hazard assessment purposes, the geological/geomorphological maps of glacial and periglacial environments should be realized at a proper scale (1:10,000 or higher) and with criteria highlighting the proneness of the mapped features to instability (Turconi, Tropeano, Savio, De, & Mason, 2015) We applied this approach to the glaciated and recently (post-LIA) deglaciated areas at the head of the Orco Valley (Figure 1), for which we provide detailed maps (Main Maps), that have been conceived as a tool for the identification of areas prone to natural instability in a context of climate warming, while maintaining rigorous cartographic standards.

Data and methods

Geomorphology of the Little Ice Age glaciated area

Maps of the slope instability events

Geomorphological analysis

Starting points of natural instability processes

Concluding remarks