Two-Channel System Dynamics of the Outer Weser Estuary—A Modeling Study

Jannek Gundlach,Zheng Bing Wang,Anna Zorndt,Bram C Van Prooijen

doi:10.3390/jmse9040448

Abstract

In this paper, we unravel the mechanisms responsible for the development of the two-channel system in the Outer Weser Estuary. A process-based morphodynamic model is built based on a flat-bed approach using simplified boundary conditions and accelerated morphological development. The results are analyzed in two steps: first, by checking for morphodynamic equilibrium in the simulations and second, by applying a newly developed method that interprets simulations based on categorization of the two-channel system and cross-sectional correlation analysis. All simulations reach a morphodynamic equilibrium and develop two channels that vary considerably over time and between the simulations. Variations can be found in the location and depth of the two channels, the development of the dominant channel over time and the alteration in the dominance pattern. The conclusions are that the development of the two-channel system is mainly caused by the tides and the basin geometry. Furthermore, it is shown that the alternation pattern and period are dependent on the dominance of the tides compared to the influence of river discharge.

Highlights

IntroductionIts morphological pattern is characterized by a distinctive two-channel system in the Outer Weser part
The Weser estuary is one of the four estuaries in the German Bight
For the base case simulation, the criteria for morphodynamic equilibrium are reached after 650 years according to Figure 6

Summary

Introduction

Its morphological pattern is characterized by a distinctive two-channel system in the Outer Weser part. In the late 19th century, a combination of increased navigational depth requirements and the limitation of navigational space due to morphological alternations [2] led to the construction of training walls and groynes [3,4] plus capital dredging [5]. Those anthropogenic interventions minimized the natural fluctuations in the position and dimensions of the two-channel system and permanently constrained the marine traffic to the main channel. Large-scale features, such as the main channel(s), dividing shoals or branching side-channels, can be found commonly [9,10]

Objectives

Methods

Results

Discussion

Conclusion