Morphometric and morphotectonic indexes for quantitative geomorphology analysis of the Cannobino drainage basin (Piemonte, NW Italy)

Preliminary studies have been conducted in the mountain area of Northern Piemonte (NW Italy) for characterization of the Cannobino drainage basin through morphometrics and morphotectonics indexes. From the geological point of view the valley belongs to the Southern Alps and his Hercynian basement is divided in two units: Ivrea-Verbano Zone (IVZ) and Serie dei Laghi (SDL). These units are separated by two discontinuities: the Cossato-Mergozzo-Brissago and Pogallo lines. The IVZ outcrops in the northern sector of the basin; main rocks types are: migmatized metapelitic schists (Kinzigite), amphibolites and mafic stratified complex (granulite, metagabbros and peridotite). SDL outcrops In the southern and central sector. It is divided in two complex: Scisti dei Laghi (metasedimentary schists, orthogneisses) and Strona-Ceneri (paragneiss, schists). A DEM (5x5 meters, Piemonte Region) of the Cannobino drainage basin has been imported into the GIS environment in order to evaluate the basin and river network’s geomorphometry. The workflow included several steps: a) lineament features digitalisation and interpretation; b) drainage network extraction and hierarchization; c) azimuthal distribution of drainage pattern; d) evaluation of linear and areal indexes: drainage density, bifurcation ratio, stream frequency, texture ratio, hierarchicalanomaly index, elongation ratio, hypsometry integral and curves, transverse topographic symmetry factor, amplitude of relief, normalized stream length index. The valuesofthese parametershave been interpolatedby meansofgeostatisticalalgorithms for the creation of different thematic maps. Furthermore, majors morphometric parameters have been identified: the significance of their geomorphic role have been evaluated by means of principal component analysis (PCA), and the statistical relationships with different type of rocks has been investigated.