Morphometric analysis of the drainage network in the Modena and Reggio Emilia Apennines (Northern Italy)

This paper deals with quantitative geomorphic analysis in the catchment basins of the rivers Secchia and Panaro, in the Modena and Reggio Emilia Apennines (northern Italy).The research is based on widely experimented methods in several Apennine basins, especially in central Italy. The aim of the research is therefore to carry out a preliminary morphometric characterisation of the Emilia basins in order to allow their correct management, also by means of sample monitoring.Using calculation algorithms based on models extensively described in literature, numerical elevation data (DEM), resulting from the interpolation of the contour lines of the Regional Technical Maps at a 1:25,000 scale, have been elaborated. In this way it was possible to extract automatically the drainage networks of the catchment basins of the Modena and Reggio Emilia Apennines.The single watercourses and relative basins have been univocally index-linked. The elaboration of a relational cartographic data bank has allowed the most commonly used hydrological parameters to be extracted by means of spatial analysis: Frequency of channels (F), Length of channels (L), Area of catchment basins (A), Ratio between area and length, Drainage density (D). From these basic parameters the most common ratios and indexes have been derived: Mean bifurcation ratio (Rb), Direct mean bifurcation ratio (Rbd), Bifurcation index (R), Hierarchic anomaly (Ga), Hierarchic anomaly density (ga), Hierarchic anomaly index (Äa), Extension ratio (Re), Circularity ratio (Rc). Subsequently, hypsometric analysis was carried out and finally, on the basis of empirical equations well known in literature, the annual unitary stream load has been assessed (Tu).The various parameters extracted have been compared with the lithological, structural and acclivity characteristics of the area, in the attempt to formulate hypotheses on the different role that the latter have played in relation to the morphodynamic evolution of the hydrographic network within the study area.The analysis of contour lines has provided us with information on the type of geomorphological evolution of the basins in relation to both the structural and lithological characteristics of the area and the distribution of the prevailing modelling processes. The assessment of stream load is consistent with the scanty data experimentally measured along the main watercourses in the pre-war period.