Modeling Estuarine Morphodynamics under Combined River and Tidal Forcing: UNESCO-IHE PhD Thesis, 1st Edition (Paperback) book cover

Modeling Estuarine Morphodynamics under Combined River and Tidal Forcing

UNESCO-IHE PhD Thesis, 1st Edition

By Leicheng Guo

CRC Press

216 pages

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Paperback: 9781138027503
pub: 2015-01-14
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Description

This research is dedicated to studying longterm estuarine morphodynamic behavior under combined river and tidal forcing. Analysis of river tides in the Yangtze River estuary (YRE) in China, schematized morphodynamic modeling in 1D and 2D mode and morphodynamic modeling of the YRE based on a process-based numerical model (Delft3D) are conducted. Morphodynamic sensitivities to river discharge magnitude and time variations, tidal strength and tidal constituents are then systematically explored.

Analysis of river tides in the YRE reveals strong river-tide interactions and non-linear modulation of tides by river discharge. River discharge alters tidal asymmetries and resultant tidal residual sediment transport.

Analysis of morphodynamic modeling results exposes significant mechanisms inducing tidal residual sediment transport and controlling long-term morphodynamic development. Morphodynamic equilibria in 1D and 2D simulations can be defined by vanishing gradients of tidal residual sediment transports and meeting empirical morphodynamic relationships.

This research indicates the value of numerical modeling in examining long-term morphodynamic development in millennia time scale. Understanding of the controls on morphodynamic behavior in estuaries under river and tidal forcing is to the benefit of managing estuaries’ functions in a long-term point of view.

Table of Contents

Abstract

1. Introduction

1.1. Definition and classification of estuaries

1.2. Driving forcing and morphodynamics

1.2.1. River flow and tides

1.2.2. Estuarine morphodynamics

1.3. Morphodynamic modeling

1.4. Objectives and research questions

1.5. Thesis organization

2. Inspiration from the Yangtze River estuary

2.1. Introduction

2.2. Driving forces

2.2.1 River discharge

2.2.2. Sediment discharge

2.2.3. Tides

2.2.4. Estuarine circulations

2.3. Sediment transport dynamics

2.4. Morphodynamics

2.4.1. Millennial geomorphological evolution

2.4.2. Centennial morphodynamic evolution

2.5. Concluding remarks

3. River tidal dynamics

3.1. Introduction

3.2. Setting, data and methods

3.2.1. Introduction to the Yangtze River estuary

3.2.2. Data source

3.2.3. Tidal analysis methods

3.2.4. Numerical model setup

3.3. Data analysis results

3.3.1. Subtidal variations

3.3.2. Time-frequency spectra of tidal species

3.3.3. Time-frequency spectra of tidal constituents

3.3.4. Time-frequency structure of tidal currents

3.3.5. Numerical model results

3.4. Discussion

3.4.1. Non-linear tidal interactions

3.4.2. River-tide interferences

3.4.3. How important is friction to tidal dynamics?

3.4.4. Implications of river tidal dynamics

3.4.5. Thoughts about river tide analysis

3.5. Conclusions

Appendix A. Harmonic analysis results

4. Role of tides

4.1. Introduction

4.2. Model setup

4.3. Model results

4.3.1. Morphodynamic development

4.3.2. Tidal hydrodynamics

4.3.3. Modeled TRST

4.3.4. Analytical TRST

4.4. Discussion

4.4.1. TRST by multiple tidal asymmetries

4.4.2. Impact of river flow on TRST

4.4.3. Rethinking the concept of representative tides

4.4.4. Feedback to reality

4.5. Conclusions

5. Role of river discharge magnitude

5.1. Introduction

5.1.1. Tidal hydrodynamics and sediment transport

5.1.2. Modeling efforts on estuarine morphodynamics

5.1.3. Aim and methodology

5.2. Model setup

5.3. Model results

5.3.1. Hydrodynamics of the schematized model

5.3.2. Morphodynamics of the schematized model

5.3.3. Tidal residual sediment transport

5.3.4. Mechanism analysis

5.4. Discussion

5.4.1. Impact of basin geometry

5.4.2. Role of river discharge

5.4.3. Morphodynamic equilibrium

5.4.4. Shape of equilibrium profiles

5.5. Conclusions

6. Impact of river discharge seasonality

6.1. Introduction

6.2. Model setup

6.2.1. Model schematization

6.2.2. Sensitivity scenarios

6.3. Model results

6.3.1. Sediment transport and fluxes

6.3.2. Morphodynamic sensitivity of hydrograph schematization

6.3.3. Morphodynamic sensitivity of hydrographs

6.4. Discussion

6.4.1. River-tide interactions

6.4.2. Hydrograph schematization

6.4.3. Morphodynamics by seasonally varying river discharges

6.4.4. Impact of extreme floods

6.4.5. Thought about MF approach

6.5. Conclusions

7. Fluvio-deltaic morphodynamics

7.1. Introduction

7.2. Model descriptions

7.3. Model results

7.3.1. Morphodynamics

7.3.1.1. Morphodynamic sensitivity to river discharge

7.3.1.2. Morphodynamic sensitivity to tides

7.3.1.3. Hypsometry

7.3.1.4. Flat areas and channel volumes

7.3.2. Tidal hydrodynamics

7.3.3. Residual currents and residual sediment transport

7.3.4. Sediment budget

7.4. Discussion

7.4.1. Channel-shoal patterns

7.4.2. Impact of river discharge 0n 2D morphodynamics

7.4.3. Impact of tides on 2D morphodynamics

7.4.4. Morphodynamic equilibrium in a fluvio-deltaic system

7.4.5. Transition between river and tide dominance

7.5. Conclusions

8. Modeling the Yangtze River estuary

8.1. Introduction

8.2. Model setup

8.2.1. One-dimensional model setup

8.2.2. Two-dimensional model setup

8.2.3. Model calibration

8.3. Model results

8.3.1. One-dimensional modeling of the South Branch

8.3.2. Two-dimensional modeling of the South Branch

8.3.3. Two-dimensional modeling of the entire estuary

8.4. Discussion

8.4.1. Impact of river and tides

8.4.2. Channel patterns in river-influenced estuaries

8.4.3. Morphodynamic time scales and equilibrium

8.5. Concluding remarks

9. Conclusions and reccomendations

9.1. Concluding remarks

9.1.1. Introduction

9.1.2. Answering the research questions

9.1.3. Overall conclusions

9.1.4. Implications for the YRE

9.2. Recommendations

References

Acknowledgements

Exposure

About the author

About the Series

IHE Delft PhD Thesis Series

IHE Delft PhD programme leads to a deepening of a field of specialisation. PhD fellows do scientific research, often with conclusions that directly influence their region. At IHE Delft, PhD researchers from around the world participate in problem-focused and solution-oriented research on development issues, resulting in an inspiring research environment. PhD fellows work together with other researchers from many countries dealing with topics related to water and the environment.

PhD research is often carried out in the ‘sandwich’ model. Preparation and final reporting – the first and last portion of the programme – are carried out in Delft, while actual research is done in the fellow’s home country, under co-supervision of a local institute. Regular contacts with the promotor are maintained through visits and long-distance communication. This enables researchers to employ solutions directly to problems in their geographical region.

IHE Delft PhD degrees are awarded jointly with a university. The degrees are highly valued and fully recognised in all parts of the world.

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Subject Categories

BISAC Subject Codes/Headings:
SCI026000
SCIENCE / Environmental Science
TEC009110
TECHNOLOGY & ENGINEERING / Civil / Dams & Reservoirs
TEC010030
TECHNOLOGY & ENGINEERING / Environmental / Water Supply