Model framework for storm surge forecasting in Venice Lagoon: what-if scenario with movable barriers

IntroductionThe Venice Lagoon is increasingly vulnerable to extreme storm surges, with the Experimental Electromechanical Module (MoSE) movable barrier system serving as its primary defense mechanism.MethodsThis study presents a novel approach to modeling storm surge dynamics in the Venice Lagoon by incorporating an immersed boundary (IB) method within the SHYFEM-MPI ocean circulation model to simulate the effects of MoSE barriers during extreme events. The methodology was validated using a simplified test case, in which the numerical barrier approach was compared with standard boundary methods to assess its reliability. The model was subsequently applied to re-forecast the November 2022 event, one of the most extreme storm surges recorded in the northern Adriatic Sea. High-resolution downscaled simulations of the Venice domain were forced using MedFS forecast data from Copernicus Marine Services, demonstrating the capability to forecast storm surges from the regional Mediterranean scale to the urban scale.ResultsThe simulations demonstrated the capability of the proposed framework to accurately forecast storm surges within the lagoon, producing water-level predictions consistent with tide-gauge observations when the MoSE system was active. A comparison between what-if scenario (i.e. unregulated) and the MoSE-regulated Lagoon showed that barrier activation reduced sea levels by up to 1 m. Analysis of partial and selective numerical barrier activation scenarios further show that different operational configurations produce distinct impacts on lagoon dynamics. Partial activation resulted in reduced and delayed sea-surface-height peaks and slower water-level decrease during ebb-tide phases. Even when selected inlets remained open, sea levels were substantially lower than under fully open lagoon conditions.DiscussionThe results highlight the effectiveness of the immersed boundary approach for representing movable barriers in operational storm surge simulations and demonstrate the significant influence of MoSE operational configurations on lagoon dynamics. The findings suggest that the barrier system can provide substantial flood mitigation even under partial operation, supporting its use in forecasting and decision-making for extreme storm surge events.