The hydromorphological state in mountain rivers subject to human impacts: a case study in the North-West of Italy

The aim of this paper is the evaluation of the hydromorphological conditions of mountain rivers subject to extensive human activities. The hydromorphological state of a river depends on a high number of natural and anthropogenic characteristics, such as the presence of weirs, dams, or any other human infrastructure close to the riverbanks. The research focused on the mountain streams in Lake Maggiore catchment, located in the Italian Alps. The analyses were carried out using the method CARAVAGGIO (Core Assessment of River hAbitat VAlue and hydromorpholoGIcal cOndition), which complies with the EC Water Framework Directive. An intensive campaign of field surveys was conducted and a great amount of data was collected to obtain specific synthesis indexes. In particular, the Habitat Quality Assessment (HQA) and the Habitat Modification Score (HMS) were used to determine the diversification of natural characteristics and the level of hydromorphological alteration in the study area. Furthermore, a Lentic-lotic River Descriptor (LRD) was used in support of the information obtained by HQA and HMS. This research shows that the worst hydromorphological conditions can be found in rivers characterised by a high level of human constructions and hydropower plants. Finally, regression analyses were implemented to search a relationship between HQA, HMS and some morphological parameters. LRD was correlated to some hydraulic parameters. The results of this research are characterised by a high stochasticity.