Hydrodynamic analysis of Lima River estuary, Portugal, based on numerical simulations

Abstract The complexity involved in the sustainable management of coastal zones, with their economic and socio-environmental importance, requires a sound knowledge of their hydrodynamics, which are directly influenced by river discharges and ocean tides, but can also be influenced by morphological changes of beds and stratification conditions. This work implemented a two-dimensional hydrodynamic model, using Delft3D software developed by Deltares for analysis of hydrodynamic patterns in the Lima River estuary, Portugal. Water levels and velocities were simulated, considering extreme river discharges and high tides of tidal waves. The model was calibrated using hydrometric field data from the measurement of water levels at four specific locations, showing a good correlation between the measured and simulated water levels, with slight deviation in the low tide period. For Nash-Sutcliffe efficiency metrics (NSE), for example, with the exception of Lanheses2 station (with NSE = 0.87), the other three monitored stations showed NSE above 0.94. The model was strong and was capable of representing real phenomenon and allowing the characterization of hydrodynamic behavior in different scenarios of river discharges and tides. The areas susceptible to flooding as well as the influence the flow and ocean tides have on the hydrodynamics were numerically analyzed. The results showed a greater influence of river flow on the water levels within the estuary, with the tide exerting greater influence in the interior of the estuary, especially in low river flow scenarios. The model can be considered an important tool for the study and management of Lima River estuary, and its capabilities will be extended to morphodynamic and stratification simulations using field data that is being collected.