GPS- RTK approach in avalanche monitoring: the Lavancher (AO) case study

Avalanches are risk factors for natural and anthropogenic ecosystems; moreover the continuous expansion of tourist settlements and outdoor activities in mountain areas increase the impacts of these phenomena. Studies and monitoring activities of these events deserve the employment of the state of the art of measurement and analysis tools, in order to improve the knowledge of the phenomenon and its dynamics. The studied avalanche is located in the municipality of Lavancher (AO), near Courmayeur (NW-Italy), and is characterized by a high avalanche frequency, with catastrophic dimensions and casualties, too. This paper presents an integrated measurement procedure with the employment of geomatic methodologies and in particular it describes the avalanche deposit measurement carried out by GPS receivers in RTK mode. Contemporarily to the survey, snow samplings have been accomplished with the purpose of estimating physical and chemical snow parameters; the use of GPS has allowed the georeferencing of sampling sites, too. In order to estimate the deposit volume, a second survey has been executed, after the deposit was completely melted, to measure bare soil morphology: surfaces obtained by the interpolation of the two surveys have allowed computing the snow deposit volume and thus the estimation of transported sediment quantity. The RTK mode has allowed the execution of each survey campaign in one day assuring centimetric precision: the results, already processed in real time, have been immediately available to the following analyses. The described methodology has thus allowed compiling an operative protocol that aims to guarantee a fast measurement execution, a reduced permanence in deposit zone – increasing the operator safety – and a high precision avalanche data, necessary for specific researches on chemical and physical properties of snow avalanche or for numerical modelling purposes.