Salt Intrusion, Tides and Mixing in Multi-Channel Estuaries: PhD: UNESCO-IHE Institute, Delft

by Nguyen Anh; Duc

• ISBN13: 9780415471220
• ISBN10: 0415471222
• Edition: 1st
• Format: Nonspecific Binding
• Copyright: 2008-11-04
• Publisher: CRC Press

Summary

Multi-channel estuaries, such as the Mekong Delta in Vietnam and the Scheldt in the Netherlands, have characteristics of both the river and the sea, forming a unique environment influenced by tidal movements of the sea and freshwater flow of the river. There are a number of knowledge gaps in understanding multi-channel estuaries. There is lack of a predictive steady state salt intrusion model where the dispersion coefficient should be predictive, in order to adequately manage salinity problems. Determination of the fresh water discharge is complicated, and there is no effort to use an analytical model to estimate the discharge distribution over branches of a multi-channel estuary. Large-scale residual ebb-flood channel circulation is an important mechanism for moving pollutants and transporting salinity upstream against a mean discharge of fresh water, for which no adequate theory exists as yet.

Table of Contents

Preface	p. vii
Summary	p. ix
Introduction	p. 1
Introduction	p. 1
Main study areas	p. 2
Mekong Delta	p. 2
Scheldt estuary	p. 4
Research challenges and objectives of the study	p. 5
Research approach and outline of the thesis	p. 6
Salt intrusion, Mixing and Tides in estuaries	p. 9
Introduction	p. 9
Classification of estuaries	p. 9
Oceanographic classification	p. 11
Classification by tides	p. 11
Geomorphology classification	p. 12
Estuarine stratification classification	p. 13
Classification by salinity curve shape	p. 15
Classification of estuaries based a combination of estuarine characteristics	p. 16
Multi-channel estuaries	p. 16
Mixing in estuaries	p. 18
Density-driven circulation	p. 19
Tide-driven circulation	p. 21
Salt transport and salinity intrusion models in estuaries	p. 25
Salt balance equation	p. 26
Salt transport and salt intrusion models	p. 27
Tidal dynamics in estuaries	p. 34
Tidal dynamics in estuaries, an introduction	p. 35
Tidal wave characteristics	p. 36
Conclusions	p. 39
Salt intrusion in multi-channel estuaries	p. 41
Introduction	p. 41
Summary of the method	p. 43
The Mekong Delta in Vietnam	p. 45
Overview	p. 45
The shape of the Mekong Delta estuaries	p. 46
Data sets of the Mekong Delta estuaries	p. 49
Salinity computation for the Mekong Delta estuaries	p. 50
Approach 1: Analysis of individual branches	p. 50
Approach 2: Combination of two branches into a single estuary	p. 52
Validation of Approach 2	p. 52
Predictive model	p. 56
Discussion	p. 57
Conclusions	p. 58
Discharge distribution over estuary branches	p. 59
Introduction	p. 60
The Mekong Delta, Vietnam	p. 60
Freshwater discharge and topographical characteristics of the Mekong Delta	p. 61
Description of the Mekong Delta's data set	p. 63
Estimation of the discharge distribution over the Mekong branches	p. 64
Previous studies determining the discharge distribution over the Mekong branches	p. 64
Analytical equation for estimating freshwater discharge on the basis of salinity measurements	p. 65
Using the analytical salt intrusion model to compute the discharge distribution	p. 66
Salinity distribution in the Mekong branches in the dry season of 2005	p. 66
The freshwater discharge distribution in the Mekong Delta during the dry season of 2005	p. 68
The freshwater discharge distribution in the Mekong Delta at the end of the dry season of 2006	p. 71
Using a hydraulic model to compute the discharge distribution	p. 74
Schematization	p. 74
Freshwater discharge distribution	p. 75
Discussion	p. 77
Comparison between the salt intrusion and the hydraulic model	p. 77
Comparison of the salt intrusion model with other models	p. 78
Limitation of the salt intrusion model	p. 80
Conclusions	p. 81
Tidal characteristics in multi-channel estuaries	p. 83
Introduction	p. 84
Tools for investigating tidal wave characteristics in estuaries	p. 85
Set of analytical equations	p. 85
Hydrodynamic models	p. 85
Observations	p. 86
Tidal wave characteristics in multi-channel estuaries	p. 86
Mekong Delta	p. 87
Scheldt estuary	p. 94
Comparison with analytical equations	p. 101
Conclusions	p. 103
Mixing in estuaries with an ebb-flood channel system	p. 105
Introduction	p. 106
Methodology	p. 108
"Virtual laboratory" residual salt transport	p. 108
Mixing in a hypothetical ebb-flood channel estuary	p. 109
Conceptual model and analytical equation for dispersion by residual ebb-flood channel circulation	p. 113
Results	p. 118
Residual circulation characteristics of the Western Scheldt obtained from the "virtual laboratory" and the conceptual model	p. 118
Comparison between the conceptual model, the salt intrusion model and the virtual laboratory in computing the dispersion coefficient	p. 119
Application to observations in the Western Scheldt and the Pungue	p. 122
Discussion	p. 124
Conclusions	p. 126
Conclusions and Recommendations	p. 129
Conclusions	p. 129
Recommendations	p. 132
References	p. 135
List of figures	p. 145
List of tables	p. 149
Notations	p. 151
Acknowledgements	p. 155
About the author	p. 157
Table of Contents provided by Ingram. All Rights Reserved.