Assessing the morphodynamic response of human-altered tidal embayments

The morphodynamics of coastal embayments and estuarine areas are defined by the flow conditions since tidal, wind and wave–induced currents are the main drivers of the sediment transport. In turn, gradients in the resulting sediment transport define sedimentation/erosion patterns and hence the morphodynamic evolution of these systems. Any modification on the average flow conditions, such as those generated by human interventions (i.e. bridge, port constructions or dredging interventions), can be considered as a potential driver inducing morphodynamic changes. This work analyzes the effect of human interventions in estuarine areas and coastal embayments and explores the applicability of tidal asymmetries and residual currents as a proxy for the prediction of the morphodynamic consequences of these interventions. A calibrated and tested numerical model with hydrodynamic and morphodynamic modules is used to compare the variations of tidal asymmetries and residual transport with the bed level evolution in a highly altered bay (Cádiz Bay, Southern Spain). Results show that the future development of the bay will heavily depend on human interventions. The agreement between the morphodynamic tendencies obtained after the analysis of the hydrodynamic variations for the altered scenarios, and the results of the morphodynamic simulations confirms the applicability of the hydrodynamic simulations as a proxy for the morphodynamic evolution. This is of special interest for any other similar coastal embayment or estuary where morphodynamic data are scarce or the calibration of morphodynamic models is too complex.