The increase of imperviousness due to urbanization creates adverse effects on the hydrological and environmental processes in a catchment. The increase in impervious areas leads to a higher runoff peak flow and stormwater pollution, even for a short duration of low-intensity rainfall. The present study focuses on the Bivio Vela catchment, an urban catchment of Pavia in northern Italy. This paper emphasizes both experimental and modeling approaches to the rainfall-runoff process and pollutant dynamics on the catchment surface and in the combined sewer system, considering significant increases in impervious area. Recent and future catchment developments caused the conversion of approximately 33% of the total area from nonurban pervious area to impervious area. The study also deals with the performance assessment of the wet-weather control system of the catchment, introducing simple indicators that account for the requirements of the urban drainage system and treatment plant. Imperviousness associate...

Analyses of six daily rainfall series (Milano, Bergamo, Brescia, Como, Mantova, and Sondrio) are used to assess trends in yearly precipitation behaviour (precipitation height and number of wet days; precipitation height and number of wet days for different classes of daily precipitation; precipitation height related to one wet day; number of dry days between wet days) over Lombardia, northern Italy. The time series analysis was performed with two non‐parametric rank based tests: the Mann Kendall test and Sen's estimator of slope. Also a new and advantageous procedure that combines a time series model and Bayesian statistics through the Markov Chain Monte Carlo (MCMC) method of Gibbs sampling is adopted to model trends. Globally, the different methods detect the same tendencies. The results point toward a significant decreasing trend in the annual number of wet days and an increasing tendency in the mean and maximum precipitation height related to one day, with a generalized increasing tendency for the number of dry days between wet days. These trends affect the rainfall runoff process and the pollutant dynamics on urban areas and in drainage systems and could provoke a significant efficacy reduction of existing urban quantity and quality control systems. Copyright © 2011 Royal Meteorological Society

Build-up/wash-off models were originally developed for small-scale laboratory facilities with uniform properties. The effective translation of these models to catchment scale necessitates the meticulous calibration of model parameters. The present study combines the Mat-SWMM tool with a genetic algorithm (GA) to improve the calibration of build-up and wash-off parameters. For this purpose, Mat-SWMM was modified to equip it with the capacity to provide comprehensive water quality analysis outcomes. Additionally, this research also conducts a comparative examination of two distinct types of objective functions in the optimization. Rather than depending on previous literature, this study undertook a numerical campaign to ascertain an appropriate range for the relevant parameters within the case study, thereby ensuring the optimization algorithm's efficient functionality. This research also implements an integrated event calibration approach, i.e., a novel method that calibrates all rainfall events collectively, thus improving systemic interaction representation and model robustness. The findings indicate that employing this methodology significantly enhances the reliability of the outcomes, thereby establishing a more robust procedure. The first objective function (TSS instantaneous less squared difference function, OF 1), which is widely employed in the literature, was designed to minimize the difference between observed and predicted instantaneous Total Suspended Solids (TSS) concentrations. In contrast, the second function (mass and mass peak consistency function, OF 2) considers integral model outputs, i.e., the overall mass balance, the time of the peak mass flow rate, and its intensity. The analysis of the outputs revealed that both objective functions demonstrated sufficient performance. OF 1 provided slightly better performance in predicting the TSS concentrations, whereas OF 2 demonstrated superior ability in capturing global event characteristics. Notably, the optimal parameter set identified through OF 2 aligned with the physically plausible ranges traditionally recommended in technical manuals for urban catchments. In contrast, OF 1's optimal set necessitated an expansion in the acceptable parameter ranges. Finally, from a computational burden viewpoint, OF 1 demanded a significantly higher number of function evaluations, thus implying an escalating computational cost as the range expands. Conversely, OF 2 necessitated fewer evaluations to converge toward the optimal solution.

The Vajont disaster was caused in 1963 by a landslide of about 270 million cubic meters that fell into a hydroelectric reservoir and generated a wave about 200 m high which overtopped the dam and caused 1917 casualties. With the aim of assessing why the real wave height was underestimated, a series of two-dimensional experiments were performed at the University of Padua in 1968 considering a scale characteristic cross section of the Vajont basin near the dam: the landslide was pushed into the stored water by a moving plate over the sliding surface and the maximum wave run-up along the opposite mountain side was measured as a function of the landslide falling time. Some of these results have been compared to smoothed particle hydrodynamics numerical simulations in which both water and noncohesive sediment are simulated as weakly compressible fluid; water is treated as Newtonian fluid while a proper rheological model is adopted for the landslide to mimic its non-Newtonian behavior. The computed fall...