Geomorphometry and Geographic Information System for the quantification of the erosive effects in Miscano River basin (Southern Italy)

The investigated area, the Miscano river basin in Campania (Southern Italy), is a territory interested by marly and clayey lithologies, whose prevalent land use is agricultural and woodland. In general, the area is characterized by a typically Mediterranean climate with rainy season during winter, and summer aridity in July and August. The monthly average temperature is included from a minimum of 3°C and a maximum of 22°C. The lowlands and hilly areas are characterized by a sub-humid to sub-arid climate; generally, the mountain areas are affected by a climate more humid. The mean annual unitary suspended sediment yield (Tu) is the principal parameter utilised to valuate indirectly the erosion rates. As it’s well known, the use of this approach is much faster since it requests few morphometric parameters calculable through statistic-mathematic method. To elaborate and to analyse the morphometric basin data collected, a software was used. This evaluation has been possible thanks to a creation of a dataset with attached database and of thematic maps. These instruments are able to give information in short time about relations between geo-environmental factors and Suspended Transport. To obtain these results two procedures were used. The first one is semi-automatic, while the second one is an automatic procedure. In the first case, the hydrographic network was derived, hand digitising in a GIS, through cartography and aereal photography analysis of the study area. Moreover, every hydrographic network was correlated to a database, which provides information to evaluate different index of geomorphic quantitative analysis, and to compose the thematic maps such as the one related to the Drainage Density referred to a sub-basin scale or the mean annual unitary suspended sediment yield in the basin. Related to the automatic procedure, it was possible to calculate other geomorphic parameters, such as the Relief Energy or the Stream Power Index, only using the Digital Terrain Model (DTM). Furthermore, it was possible to calculate different value of Drainage Density for every single lithologic complex and land use unit (parameter of Drainage area Density), and the Drainage Density using a basin obtained from the DTM too. Also for this procedure, the elaboration and the analysis were presented in thematic maps. Accordingly, the hydrographic network, which have a Drainage Density value near to 6, are conditioned by the presence of hierarchical anomalies, both as the high SPI and the medium-high Er values. Furthermore, it was possible to define the stages of evolution of hydrographic network especially the young phase, according to Davis Cycle, and some cases of rejuvenation. Ultimately, it’s possible to affirm that thanks to GIS, the Quantitative Classic Geomorphic Analysis can be applied to river contexts far to normality, in according to the definition of Horton and Strahler. This application can be applied, spending short time, at a regional scale and can be useful to create cartographic maps easy to update and to consult.