Geomorphological aspects of the flood hazard in the area between the rivers Po, Secchia and Panaro (Po Plain, Northern Italy)

This paper examins the geomorphological aspects of the flood hazard in the area between the rivers Po, Secchia and Panaro. The River Po, which flows in the northern part of the study area, and the Rivers Secchia and Panaro, which flowing northwards cross the study area, have periodically caused flooding in their territory. The flood hazard, related to morphological factors, is much higher in the sector north of Modena (where the rivers flow elevated over the surrounding plain between high banks) than in the sector south of the town (where the watercourses run deep in the alluvial plain). North of Modena. in order to defend the territory from the flood hazard the systematic practice to build, strengthen and increase in height artificial banks was adopted. Moreover several meander cuts were carried out along the Rivers Secchia and Panaro (the length reductions correspond to about 11÷12% of their overall length in the plain). As these interventions resulted to be ineffective, flow-regulation systems were constructed in the area of Modena along both rivers. They consists of a regulating dam built across the riverbed and a storage basin bordered by embankments. The historical flood events show that the banks breaches often occured near to paleochannels and that the flooded waters were collected in the lower areas and had as boundaries the embankements and/or the fluvial ridges flanks; sometimes the flooded waters remained for long periods in the areas where mainly clay superficial deposits crop out. Therefore, an important contribution to assess the flood hazard can be given by the geomorphological investigation through the implementation of GIS georeferenced thematic documents (Digital Elevation Model, microrelief, surface deposits and geomorphological maps) and related Data Base.