Morphodynamic Equilibria in Double‐Inlet Systems: Existence and Stability

Journal of Geophysical Research Earth Surface, vol. 126

Abstract

Abstract The existence of morphodynamic equilibria of double‐inlet systems is investigated using a cross‐sectionally averaged morphodynamic model. The number of possible equilibria and their stability strongly depend on the forcing conditions and geometry considered. This is illustrated by considering a rectangular double‐inlet system forced by M2 tidal constituents only. Depending on the M2 amplitudes and phases at both entrances, no equilibrium, one equilibrium or multiple morphodynamic equilibria may exist. In case no equilibrium is found, the minimum water depth becomes zero somewhere in the system, reducing the double‐inlet system to two single‐inlet systems. In the other cases, the location of the minimum water depth and the direction of the tidally‐averaged sediment transport, as well as their actual values, depend strongly on the M2 tidal characteristics. Such parameter sensitivity is also observed when including the residual and M4 forcing contributions to the water motion, and when allowing for width variations. This suggests that, when considering a specific system, the number and stability of morphodynamic equilibria, as well as the characteristics of these quantities, can only be assessed by investigating that specific system in detail. As an example, the Marsdiep‐Vlie inlet system in the Dutch Wadden Sea is considered. It is found that, by using parameter values and a geometry characteristic for this system, the water motion and bathymetry in morphodynamic equilibrium are qualitatively reproduced. Also the direction and order of magnitude of the tidally‐averaged suspended sediment transport compare well with those obtained from a high‐complexity numerical model.

Authors 6

1. Xiao Gang Deng corresponding

   Delft University of Technology

   Affiliation as printed

   Department of Applied Mathematics Delft University of Technology Delft The Netherlands

   Department of Applied Mathematics, Delft University of Technology, Delft, The Netherlands

2. Corine Meerman Aachen Mathematical Institute

   Leiden University

   Affiliation as printed

   Mathematical Institute Leiden University Leiden The Netherlands

   Mathematical Institute, Leiden University, Leiden, The Netherlands

3. Thomas Boelens

   Ghent University

   Affiliation as printed

   Hydraulics Laboratory Department of Civil Engineering Ghent University Ghent Belgium

   Hydraulics Laboratory, Department of Civil Engineering, Ghent University, Ghent, Belgium

4. Tom De Mulder

   Ghent University

   Affiliation as printed

   Hydraulics Laboratory Department of Civil Engineering Ghent University Ghent Belgium

   Hydraulics Laboratory, Department of Civil Engineering, Ghent University, Ghent, Belgium

5. Paulo Salles

   Instituto de Ingeniería · Universidad Nacional Autónoma de México

   Affiliation as printed

   Instituto de Ingenieria Universidad Nacional Autónoma de México Sisal Mexico

6. Henk M. Schuttelaars

   Delft University of Technology

   Affiliation as printed

   Department of Applied Mathematics Delft University of Technology Delft The Netherlands

   Department of Applied Mathematics, Delft University of Technology, Delft, The Netherlands