Definizione della pericolosità da fenomeni torrentizi, l’esperienza della provincia di Trento

Ruggero Valentinotti (1), Gabriele Bertoldi (1), Carla Pendino (1) & Stefano Fait (1)
(1) Servizio Bacini Montani, Provincia Autonoma di Trento, Via G.B. Trener, 3 - 38100 - Trento Corresponding author e-mail: ruggero.valentinotti@provincia.tn.it

The regulation concerning flood hazard mapping in Provincia di Trento have been developed coherently with the Flood Directive, and hazard maps are prone to continuous updates and improvements. However hazard mapping is costly and involve sources of uncertainty often not negligible and not reducible, and several efforts has been done to realize empirical tools to support decision both at fan and regional scale. Considering a system formed by hydrological network, catchment and fan , morphological, pluviometric, soil and geology parameters are evaluated at regional scale in Trentino for all the basins with an area under 10 km2 and compared with the occurrence of debris flood events. The event inventory of the Provincia di Trento includes about 3500 events of which about 1500 debris flow. Only 175 debris flow events are recorded on the fans. Using a morphologic survey of the fan, 1697 systems under a basin area of 10 km2 has been mapped, of which 579 have a relevant anthropic activity on the fan. Parameters are selected with autocorrelation test and logit general linear model has been used in order to determine a binary propensity of a system to be prone to debris flow. In order to try to reduce non stationary sources of bias, three model are evaluated, considering all the suitable data, only systems with relevant human activity on the fan and only debris flow events after 1980. Models obtained are convergent and are based on the fan area, a geological index, the maximum altitude and the 1h , 100 years return period rainfall quantile, that is inversely related. The investigation stress the importance of data management for public stakeholder involved on hazard mapping, and underline the needed of further investigation on tool to support catchment analysis.

fenomeni torrentizi, eventi alluvionali, pericolosità, colate detritiche, probabilità di accadimento.