From geotechnical and hydraulic researches to use of natural materials in mitigation works for river embankments: a case of study

In rivers, a hydraulic hazard is the result of natural or human factors, or both. The first step in addressing the problem is to establish hydraulic security measures; the work undertaken must allow for improving hydraulic characteristics of the river in order to create a section compatible with the maximum predictable height and flow. The logic of the mitigation works for the hydraulic hazard usually doesn’t coincide with river redevelopment measures because some actions are obviously conflicting. These questions are faced with a geotechnical and hydraulic research and with the use of natural materials in mitigation works. The study consists of a diagnosis about the conditions of functionality of the fluvial embankments (in particular in the urban section), to suggest guidelines for measures with low environmental impact and with a “friend of nature” engineering approach. In this paper the geotechnical and hydraulic problem of the existing embankments is analysed in two areas that are particularly important to the Aterno River (L’Aquila, Italy). The aims of the studies are to find the most suitable solutions of correction and restoration works. This paper illustrates the methodology to define the map of hydraulic hazard and to determine the maximum heights of the flow. Moreover, it shows the results of many in-situ tests by flat dilatometer (DMT) and laboratory geotechnical tests performed in the river alluvium soils in order to perform a stability analysis of embankments and for settlements prediction. Finally, it gives guide lines for measures with low environmental impact and with an eco-friendly engineering approach.