Morphological changes in the valley and in the upper plain of the Panaro river (Province of Modena)

The researches carried out in the last years have allowed to highlight the morphological changes in the valley and in the upper plain of the Panaro river. These studies were carried out according to the traditional methods used in geomorphology (bibliographic research; research on historical documents and maps, interpretation of aerial photographs, field-survey) as well as with methods concerning digital treatment of maps and digital ortophotographs.The Panaro River collects the waters from the central section of the Northern Apennines and flows into the River Po after running across the Modena Apennines and the Po Plain.The Panaro course in the Po Plain flows through two distinct sectors showing different geomorphological characteristics: in the upper sector of the plain the river runs deep in the alluvial plain, whereas in the mid-lower part of the plain it flows as hanging river within artificial embankments. As regards the evolution over the past two centuries, at the beginning of the 19th century the river occupied a large depression with an anastomosing overdeposited riverbed in the upper sector of the plain; in the following periods the increase of man’s interventions along the river (construction of embankments, walls and groynes), in order to protect the territory from floods and reclaim high-water areas for farming practices, led to a narrowing of the riverbeds in several points which in any case have maintained the anastomosing pattern until the 1930s. Subsequently, it turned from a braided riverbed to a canalised course subject to marked deepening; the shape of the longitudinal profile changed from a hyperbola-type curve to a step-type one.In the Panaro valley, the comparison between the topographical elements currently visible in the filed and the topographic base map (the Regional Technical Map dated to some 30 years ago) has highlighted a substantial change along the river valley. Particularly, besides a great growth of urban areas on the river terraces, the river has undercut its bed forming a new terrace. Its formation is likely to date back to the end of the seventies and the beginning of the eighties.As for the causes of these changes, mainly circumscribed to the past 50 years, the effects of natural causes seem to have played a minimal role. These modifications were in fact mainly due to gravel excavation activities along the riverbed and the construction of fluvial barrages. This evolution is similar to what has been recorded in other Italian rivers.