Author(s): Guillermo Martin-Llanes; Marta Aragon; Carmen Zarzuelo; Alejandro Lopez-Ruiz
Linked Author(s): Carmen Zarzuelo
Keywords: Estuary; Convergence; Salt intrusion; Resilience
Abstract: Alluvial estuaries, which are considered to be environmentally remarkable coastal areas, are suffering from the negative effects of climate change and human activities such as channel deepening and narrowing. These phenomena directly modify the external forces that determine the hydrodynamics and morphology of the estuaries, leading to changes in the salt transport mechanisms, which in turn modify both the environmental conditions and the morphodynamic response to extreme events of these coastal areas. In order to address this current problem, which is of particular concern for basin management, this paper aims to deepen the knowledge of the role of river bank convergence on the resilience of estuaries to extreme river discharge events. The resilience is measured by the change in salinity intrusion due to the increasing advective river flow and the characteristic response times (adaptation to the peak discharge and recovery to the initial conditions). To achieve this goal, a 3D hydrodynamic model is applied to a set of five idealized basins that differ in convergence length. The chosen values of this length cover estuaries from prismatic to pronounced funnel shape. The Delft3D model was used to reproduce the transport and temporal response for each scenario under different extreme river discharge events. The number of combinations between geometries (physical scenarios) and river discharge conditions is sufficient to find empirical relationships between physical characteristics of alluvial estuaries and hydrological regimes. The results are parametrized using the spatial ratio of convergence change (χ) and the magnitude of the pulse (Γ), and show that salt wedge displacement and adaptation response time maintain a quadratic relationship with χ. It also plays an important role in the structure of the density gradients that control the recovery process.
DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0629-cd
Year: 2023