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Starting from the classical conservative form of the shallow water equations, the source term of the momentum balance equation was modified to\ud increase computational stability. This was achieved by replacing the term representing the local bed slope by an alternative expression of the pressure\ud effect due to cross-section irregularities in non-prismatic channels. The resulting mathematical model turns out to be particularly suitable for complex\ud channel and natural river geometries, and also improves the computational stability for complicated flow conditions. The explicit finite difference\ud MacCormack scheme was adopted for numerical implementation. The model was thoroughly tested using a set of numerical test cases involving\ud various channel geometries and a wide range of flow conditions. The same simulations were compared also with the classical model and with other\ud schemes. Finally, a real flood event on the Italian river Reno was simulated, to confirm the model suitability for natural channels

Not only solid volumetric concentration, but also coarse particle content play a relevant role on the rheology of soil mixtures involved in mud, debris, hyper-concentrated and earth flows. This paper is devoted to investigating the influence of bulk solid volume concentration and of coarse fraction on the rheological behavior of granular slurries. Laboratory activity is carried out involving different soils from the source area of real debris flows (from the Campania region in Italy). Experimental results demonstrate that the flowing behavior is the same as yield stress fluids with a static yield stress value larger than the dynamic one. A generalized Herschel-Bulkley model is considered, accounting for a consistent index which is a function of solid

Water resource management (WRM) through dams or reservoirs is worldwide necessary to support key human-related activities, ranging from hydropower production to water allocation and flood risk mitigation. Designing of reservoir operations aims primarily to fulfill the main purpose (or purposes) for which the structure has been built. However, it is well known that reservoirs strongly influence river geomorphic processes, causing sediment deficits downstream, altering water, and sediment fluxes, leading to riverbed incision and causing infrastructure instability and ecological degradation. We propose a framework that, by combining physically based modeling, surrogate modeling techniques, and multiobjective (MO) optimization, allows to include fluvial geomorphology into MO optimization whose main objectives are the maximization of hydropower revenue and the minimization of riverbed degradation. The case study is a run-of-the-river power plant on the River Po (Italy). A 1-D mobile-bed hydro-morphological model simulated the riverbed evolution over a 10 year horizon for alternatives operation rules of the power plant. The knowledge provided by such a physically based model is integrated into a MO optimization routine via surrogate modeling using the response surface methodology. Hence, this framework overcomes the high computational costs that so far hindered the integration of river geomorphology into WRM. We provided numerical proof that river morphologic processes and hydropower production are indeed in conflict but that the conflict may be mitigated with appropriate control strategies.

An experimental study was carried out on several dense-granular mixtures (debris flow mixtures and natural sand mixtures) using several rheometrical tools in order to investigate the rheological behaviour of the "fluid-like" material mixture. The results obtained on debris flow-water mixtures suggest that, in the fluid-like regime, the typical rheological behaviour is that of yield stress fluids and the rheology is strongly dependent on the grain concentration. The velocity profile obtained on natural sand-Newtonian fluid mixtures identify the shearing zone and explain the dependence of the flow characteristics (i.e., transition from quasi-static regime to liquid regime) on viscosity and shear rate. The results suggest that, in that field, the interstitial fluid viscosity influence the sharing material layer and that no flow is possible for solid fraction higher than a maximum value.