Evaluating hydrodynamic loads on bridge piers: a pilot case study of the RISKADAPT project

The RISKADAPT project addresses the growing challenges caused by extreme weather phenomena on critical infrastructure. This study contributes to the project by assessing the hydrodynamic loads on the piers and abutments of the Polyfytos Bridge, located at the Polyfytos Lake, Greece. Specifically, it evaluates the discharge rates, water flow velocities, and water levels under present and future climate projections to understand the potential risks to this critical asset from climate-induced flooding. Climate change, through its effects on temperature and precipitation patterns, disrupts the hydrological cycle, resulting in altered river runoff regimes. The study employs hydrological and hydraulic modeling techniques to assess these impacts on critical infrastructure. A hydrological model is used to convert different precipitation scenarios into river discharges, considering present and future climate projections. Next, the hydraulic model simulation provides water flow parameters, which are the basis for estimating the risk of scour formation around the Polyfytos Bridge piers. The modeling was conducted using the HEC-RAS software. For the first phase, the study utilized extreme precipitation data with three return periods (50, 100, and 1,000 years) for present and future climates. Historical data were drawn from global extreme precipitation (GPEX) datasets, and future projections were sourced from the EURO-CORDEX dataset, encompassing 48 combinations of global circulation and regional climate models. These data were used to predict the impact of future climate scenarios on extreme discharges, with some projections indicating a decrease in extreme discharges, while others predict an increase of 48%, 46%, and 30% for the events with return periods of 50, 100, and 1,000 years, respectively. In the second phase, hydrological results were used to generate hydrographs, which served as an input for the hydraulic simulations at the Polyfytos Lake inflow. The hydraulic modeling provided key parameters, such as water depth, surface elevation, flow velocity, and discharge, essential for further scour analysis. Results indicated that the hydrodynamic loads on the bridge piers were relatively low, even under extreme flood events. Water flow velocities remained below 0.5 m/s during the 100-year flood event, suggesting a low risk of scour formation that could compromise the bridge’s stability. The analysis of future climate scenarios showed varying impacts on discharge rates, with some indicating an increase in extreme discharges. However, the conclusion was that the Polyfytos Bridge is not significantly susceptible to scour, even under the most extreme projected climate conditions.