Evaluation of Flood Peak Attenuation by the Monticano Detention Basin Using Hydraulic Modeling

The construction of detention basins is an effective solution for water storage and flood peak reduction in lowland areas, where riverbeds are typically characterized by mild slopes. This type of basin, usually enclosed by levees, is widely adopted in inhabited regions where naturally depressed areas are not available. This study focuses on the detention basin of the Monticano river, located in the municipality of Fontanelle and designed in 2022 by the request of the Veneto Region. This basin is administratively connected to the larger Prà dei Gai detention system in Mansuè. The Monticano River is one of the main tributaries of the Livenza basin. It originates in the municipality of Vittorio Veneto, and it flows into the Livenza river at Gorgo al Monticano. The combined flow subsequently reaches the Adriatic Sea near Caorle. Within the study area, two tributaries of the Monticano river are also considered. The Cervadella stream joins the Monticano river downstream the Via Ongaresca bridge, in Fontanelle. It divides the detention basin into two compartments, which are hydraulically connected by an underground siphon beneath the stream. The second tributary, the Lia stream, converges into the Monticano river in the municipality of Oderzo. The aim of this work is to evaluate the effect of the Monticano detention basin on flood peak attenuation at a downstream control section, located at the Monticano bridge in Oderzo. To this end, nine flood events are analyzed, defined by three return periods and three rainfall event durations each. The inlet and the outlet structures, which connect the river to the detention basin, as well as the interconnection structure, are modelled using MATLAB. The calibrated hydraulic model and the resulting outputs are subsequently implemented and visualized using the HEC-RAS software. Finally, the discharges and water levels obtained are compared with the Hydraulic Criticality Threshold to assess the severity of the analyzed events at Oderzo and Fontanelle cross sections.