|From chaos to stability: the development of an alternating bar-channel estuary|
de Lange, J.M. (2019). From chaos to stability: the development of an alternating bar-channel estuary. MSc Thesis. Utrecht University, Department of Physical Geography: Utrecht. 41 + appendices pp.
Marine/Coastal; Brackish water; Fresh water
Metronome, estuaries, bars, channels, bend, bar push and pull theory
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Estuaries are highly populated and of great economic and environmental importance. For the mean of accessibility of hinterland ports by large cargo ships, men influence estuaries on large scale (e.g. dredging), with that altering the behaviour of an estuary, e.g. the Western Scheldt (Swinkels et al., 2009; Bolle et al., 2010; Jeuken and Wang, 2010). Unfortunately, little is known about natural behaviour of the main shipping obstacles, namely shoals. This research studied the development of an initial straight channel to an alternating bar-channel estuary system. The analysis of this research was conducted on the data produced from a tilting flume experiment, which contained two open boundaries for the production of a symmetrical tide. To investigate the development of the alternating bar-channel system, the first 2000 cycles of the experiment, the bar-channel wave dimension and bend migration were analysed. Special attention was given to the dimensions of the bar-channel wave and the dynamics of the estuary bends. The results presented in this study point to the existence of three consecutive periods, namely: the periods of chaos, growth and stabilization. During the short period of chaos, patterns were developed from the chaotic initial state, taking roughly 400 cycles. The following 800 cycles were characterised by the largest dynamics of the estuary bends, growth of the bar-channel wave dimensions and estuary width, called the period of growth. During the last 800 cycles, these dynamics and growths stabilize, except for the decreased growth of the estuary width. Moreover, a positive linear relation was found between the bar-channel wave amplitude and the width-depth ratio of the estuary. Furthermore, the outer bends were not influenced by the inner bends rejecting bar push theory for this experiment.