Author(s): Carmen Zarzuelo; Alejandro Lopez-Ruiz; Arnoldo Valle-Levinson; Manuel Diez-Minguito; Miguel Ortega-Sanchez

Linked Author(s): Carmen Zarzuelo, Alejandro López-Ruiz, Arnoldo Valle-Levinson

Keywords: Tidal flow; Numerical model; Bridge-pile; Estuary; Hydrodynamic

Abstract: Estuarine environments are highly complex coastal systems that evolved rapidly during the Holocene transgression and were shaped by diverse interactions between hydrodynamics, geomorphology, biological activities, climatic variations, and human interventions. Hence, it is vital to analyze the effect of interventions developed in estuaries, such as dredging of waterways or construction of harbors and bridges. In particular, the bridge piles can work as an obstacle to tidal wave propagation, changing its properties and thus altering the local hydrodynamics. In this study, we assess the impact of the bridge-pilling modifications on the tidal flow at the strait of a human-altered mesotidal estuary (Cádiz Bay, Spain). This bay constitutes a singular system due to its complex geometry and the human interventions developed during last decades. The methodology is based on field data of current velocities observed in a cross-section close the pile and the application of a numerical model specifically developed for this type of environments, which has been calibrated and tested for water levels, currents, temperature, and salinity. We have also used the numerical model to check if the tidal flow behavior is due to the location of the section pier or other. We analyze how the bridge piling effects at intratidal scale during neap and spring tides, also assessing the modifications over the tidal harmonics, stratification, and the potential sediment transport due to the pile. The results show that the bay is tidally driven and laterally sheared in spring tides whereas density-driven and vertically sheared in neap tides. The assess of the semidiurnal, quarti-diurnal and sixth-diurnal (D6) bands show that the wake of the pile trigger significant variations on their amplitude and phase, also reducing the water depth of the pycnocline and altering the sediment transport. The results can be extrapolated to other field sites which are been altered by anthropogenic interventions as bridge or wave farms.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221556

Year: 2022