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Morphodynamic Equilibria in Tidal Embayments with Decreasing Cross-Section. Henk Schuttelaars The Institute for Marine and Atmospheric research Utrecht (IMAU) Utrecht University. Contents. Introduction Model Formulation Numerical Experiments Comparison with Observations
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Morphodynamic Equilibria in Tidal Embayments with Decreasing Cross-Section Henk Schuttelaars The Institute for Marine and Atmospheric research Utrecht (IMAU) Utrecht University
Contents • Introduction • Model Formulation • Numerical Experiments • Comparison with Observations • Conclusions + Future Research
Tidal Embayments: Introduction • Semi-enclosed bodies of water • Connected to the open sea • Driven by tides Examples: • Frisian Inlet System • Western Scheldt • Inlets East Coast of the US
Research Questions • Do Long-Term Equilibria Exist • Are They Unique and Stable } ? PARA- METERS
Model Formulation • Idealized Models: } Water Motion Short Time Scale Sediment Transport Long Time Scale Bed Evolution Averaging
Model Equations and Assumptions • Depth Averaged Shallow Water Equations • Only Bed Erodible • Noncohesive Material • Suspended Load Transport • Sediment Balance: Fine Sand hole bar
Geometry Side View: W Top View: W E Embayment R X=0 X=L
Parameter Continuation Short Embayment: • Analytical Solution • constantly sloping bed • spatially uniform hor and vert velocities • spatially uniform bed stress For other parameters, continue this known solution
Reducing WR Different Types of Equilibria Comparison with data The Experiments Experiment 1: Experiment 2:
M2 Phase Hor Vel 0 -10 -17 0 WR/WE -10 Depth in meters -27 Sea 110 km Land Width Variation Bed Profile WR/WE Sea 110 km Land WR/WE ~ 1 WR/WE ~ 0.5 • Bed Very Deep • Standing Wave • M4extern amplified • Bed Weakly Concave • Travelling Wave • M4extern negligible Decreasing WR
Comparison With Field Data (1) Width Width-Averaged Depth
Comparison With Field Data (2) Sea Land Sea Land
Conclusions Two Types of Equilibria: Idealized Model Reproduces Global Characteristics Quite Well Multiple Equilibria Maximum Embayment Length • externally driven • friction-related
Future Research • Closer Comparison With Process-Based Models and Observations • Introduce Two Dimensional Perturbations