Fast geomorphic transients may involve complex scenarios of sediment transport, occurring near the bottom as bed load (i.e., saltating, sliding, and rolling) or as suspended load in the upper portion of the flow. The two sediment transport modalities may even coexist or alternate each other during the same event, especially when the shear stress varies considerably. Modeling these processes is therefore a challenging task, for which the usual representation of the flow as a mixture may result in being unsatisfactory. In the present paper, a new two-phase depth-averaged model is presented that accounts for variable sediment concentration in both bed and suspended loads. Distinct phase velocities are considered for bed load, whereas the slip velocity between the two phases is neglected in the suspended load. It is shown that the resulting two-phase model is hyperbolic, and the analytical expression of the eigenvalues is provided. The entrainment/deposition of sediment between the bottom and the bed load layer is based on a modified van Rijn transport parameter, whereas for the suspended sediment a first-order exchange law is considered. A numerical finite-volume method is used for the simulation of three dam break experiments found in the literature, which are effectively reproduced in terms of both free surface elevation and bottom deformation, confirming the key role played by the solid concentration variability even for two-phase models

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The sustainable management of water supply networks requires the control of physical pipe leakages, such as those due to junction obsolescence or pipe creeping. These leakages usually increase with the operating pressure, and their discharge is commonly assumed to scale with the power of the pressure. The same functional form is also employed to evaluate leakage occurring in the portion of the network downstream a node. The parameters involved in these relationships may be estimated from field experimental data. However, a sensible fluctuation in their values is observed, and therefore the definition of a suitable leakage law represents a major source of uncertainty in water network modeling. In the present paper, the estimation of the leakage law parameters is carried out simultaneously to the hourly demand pattern. To this aim, a hydraulic network model coupled to a genetic algorithm is employed to minimize the deviation between predicted and measured time series of pressure and flow at a small number of sites of the network.A field test case is analyzed to show the effectiveness of the proposed procedure. NOTATIONc parameter of leakage law [m 3Àγ /s] C d per-capita hourly water demand [m 3 /s/inhab.] d data vector [dimensions may vary] D node outflow [m 3 /s] G(·) symbolic operator of a generic mathematical model [dimensions may vary] L leak discharge [m 3 /s] m number of parameters [-] M parameter vector for G model [dimensions may vary] N 1 exponent of leakage law [-] n h number of hours in the time pattern [-] n mP total number of pressure stations [-] n mQ total number of flow stations [-] n u,i number of users supplied by i-th node [-] OF objective function [-] P node pressure head [m] P cross crossover probability [-] Q volumetric flow [m 3 /s] γ exponent of leakage law [-] SUPERSCRIPT k hour index SUBSCRIPTS 1 pertaining to network zone 1 2 pertaining to network zone 2 C computed i node index M measured 35

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The paper investigates the impact of a dam-break wave on an erodible embankment with a steep slope. Both experimental and numerical analyses were carried out. The laboratory experiments have been specifically designed and performed, varying the storage water level, the elevation and the slope of the embankment. The simulations were carried out using a recent two-phase depth-integrated model, supplemented with a geofailure operator to account for the possible occurrence of geotechnical collapses. The comparison between the numerical and experimental results indicates that the two-phase model permits to fairly reproduce the experimental free surface elevation, with or without the geofailure operator. Conversely, especially for high embankment slopes, this operator appears to be crucial for predicting the observed morphological evolution. Moreover, the results show that, due to the geotechnical collapses, water and sediment velocities may have opposite sign. While models based on equal direction of the liquid and the solid motion cannot reproduce this issue, the proposed two-phase approach easily accounts for such a peculiarity of the investigated process

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The contamination of industrial cooling towers has been identified as one cause of legionellosis, but the real risk has been underestimated. Two different disinfection treatments were tested on Legionella colonization in an industrial Cooling Tower System (CTS). Environmental monitoring of Legionella, P. aeruginosa, and a heterotrophic plate count (HPC) at 36 °C was performed from June to October 2016. The disinfection procedures adopted were based on hydrogen peroxide (H2O2) and silver salts (Ag+), in addition to an anti-algal treatment, then using hyperclorination as a shock, and then continuous treatment by sodium hypochlorite (NaClO). L. pneumophila serogroup 8 was found at a concentration of 5.06 Log cfu/L after the CTS filling; a shock treatment performed by H2O2/Ag+ produced a rapid increase in contamination up to 6.14 Log cfu/L. The CTS activity was stopped and two subsequent shock treatments were performed using NaClO, followed by continuous hyperclorination. These procedures showed a significant decrease (p < 0.05) in Legionella concentration (1.77 Log cfu/L). The same trend was observed for P. aeruginosa (0.55 Log cfu/100 mL) and HPC (1.95 Log cfu/mL) at 36 °C. Environmental monitoring and the adoption of maintenance procedures, including anti-scale treatment, and physical, chemical, and microbiological control, ensure the good performance of a CTS, reducing the Legionella risk for public health.