G. Rasulo

Forecast model of water consumption for Naples

The data refer to the monthly water consumption in the Neapolitan area over more than a 30 year period. The model proposed makes it possible to separate the trend in the water consumption time series from the seasonal fluctuation characterized by monthly peak coefficients with residual component. An ARMA (1,1) model has been used to fit the residual component process. Furthermore, the availability of daily water consumption data for a three-year period allows the calculation of the daily peak coefficients for each month, and makes it possible to determine future water demand on the day of peak water consumption.

Combined Effects of Parallel and Series Detention Basins for Flood Peak Reduction

A simple analytical method is proposed that allows a preliminary evaluation of the overall efficiency of a detention basin system for flood risk reduction in a specific target section. Solutions are provided both for parallel and series systems, under some simplifying assumptions concerning the linearity of detention basin, river network and watershed responses. Further, for the series configuration a regressive model is proposed for the computation of the overall efficiency, because of the complexity of analytical solution. A case study is also presented, where the overall efficiency of a system of nine detention basins is computed by means of both the analytical and the regressive model. Results are discussed to assess the different influence of detention basins in parallel or in a series system.

Preliminary Estimate of Detention Basin Efficiency at Watershed Scale

Urban encroachment in natural floodplain areas and infrastructures interfering with watercourses have caused higher flood risks in lowland areas. In this context, detention basins have become a fundamental instrument for stormwater and environmental management at watershed scale. Numerical methods of flood routing are generally coupled with optimization algorithms to investigate the factors that affect the overall efficiency of detention basins in controlling the peak flows throughout a watershed. To overcome the procedure effort due to numerical integration, a simple innovative approach, based on the linear system theory applied to the solution of hydrologic flood routing, is proposed for a preliminary estimate of overall efficiency. First a numerical analysis is performed to ensure that the schematization of the detention basin as a linear system leads to technically acceptable approximation. Then, a simple analytical equation is provided that allows a preliminary estimate of detention basin efficiency in downstream river reaches. Sensitivity analysis of the above equation provides information about the factors that most contribute to the downstream flow reduction variability. Finally, the proposed methodology, adequately extended to a parallel system of stormwater detention basins within a watershed, can be easily integrated in optimization algorithms.

Design of a Scroll Vortex Inlet for Supercritical Approach Flow

Vortex drop shafts are used in urban drainage systems to connect two sewers located at considerably different elevations. After their introduction in 1947, these were studied with particular reference to subcritical approach flow. Vortex shafts for supercritical approach flow can also be used, but the intake structure may have relatively high cost due to the complex geometry. The present study includes experimental results of a specific investigation on the changes to be made in the supercritical approach channel if a subcritical vortex intake is used. The experimental investigation analyzes the effect of a hydraulic jump on the performance of vortex intake structure to define appropriate technical solutions, essentially consisting in a negative step to be located along the supercritical approach channel. Design criteria are finally presented for the evaluation of the step height and its distance from the vortex intake structure.

Vortex Drop Shaft for Supercritical Flow

Vortex drop shafts are used in urban drainage systems to connect two sewers located at considerably different elevations by means of a vertical conduit. The vortex drop shaft was first designed by Drioli (1947). It was then studied by other authors with reference to subcritical approach flow. Vortex shafts specifically conceived for supercritical flow can also used, but at very high costs due to the specially features required for the intake structure. The present study shows the experimental results of a specific investigation into the changes to be made in the approach channel for supercritical flow, when a subcritical vortex intake is used. The proposals concern the definition of the height of the step to be located in the approach channel, and the length of the lower-bottomed section in the approach channel, while maximizing the hydraulic efficiency of the system. Proper step height will cause the hydraulic jump to conveniently occur downstream of the step, whereas a regular subcritical flow in the intake structure of vortex shaft will result from lowering the bottom of the approach channel for the appropriate length.

Peak coefficients of household potable water supply

An experimental data-gathering project was carried out on two boulding aggregations of limited size in the urban area of Naples. Flow-rate measurements were continuously taken during a period of 24 h while the delivered volumes were recorded for approximately three years. The pattern of water demand in the day of maximum consumption is presented in a histogram of the hourly distribution which allows the hourly and istantaneous peak coefficients to be determined. The determination of the average daily consumption per year and the daily peak coefficient is made possible by the availability of quarterly invoicings.

Vortex shaft outlet

Vortex drop shafts are widely used in practice to connect sewer mains characterized by large elevation difference. These structures conventionally include three key elements: intake structure, vertical shaft and outlet structure, also named dissipation chamber. The latter has not received much attention as compared to the first two parts, and only few experimental investigations are currently available from the literature (Viparelli, 1950; Kellenberger, 1988). Actually some rules of thumb are available as design criteria (ATV, 1998; Hager, 1999), but no systematic hydraulic investigation is available so far. The aim of the present study is to present preliminary results of an experimental campaign conducted at the Department of Hydraulic and Environmental Engineering, University of Naples, Italy. The physical model of a vortex drop shaft allowed the Authors to investigate the main hydraulic features of the dissipation chamber, in order to characterize the performance of various types of outlet structures.