Title Page
Contents
ABSTRACT 15
CHAPTER Ⅰ. INTRODUCTION 18
References 22
CHAPTER Ⅱ. CONTRIBUTION OF LOCAL EROSION ENHANCED BY WINDS TO SEDIMENT TRANSPORT IN INTERTIDAL FLAT 28
Abstract 29
1. Introduction 30
2. Study area 32
3. Materials and methods 32
3.1. In-situ mooring and data analysis 32
3.2. Bed erosion experiments and data analysis 34
3.3. Applying erosion parameters by GEMS to in-situ measurements 36
4. Results 37
4.1. Meteorological and hydrodynamical conditions 37
4.2. Relationship between τcw and SSCT in in-situ measurements[이미지참조] 38
4.3. Bed erodibility in erosion experiments 39
5. Discussion 40
5.1. Effects of air exposure 40
5.2. Effect of sediment flux 42
5.3. Effect of erosion type 43
Conclusions 45
References 47
CHAPTER Ⅲ. SPRING-NEAP VARIATION OF FLOC IN MACROTIDAL FLAT 63
Abstract 64
1. Introduction 65
2. Study area 66
3. Materials and methods 67
3.1. In-situ mooring and data analysis 67
3.2. Properties of bed and suspended sediments 68
4. Results and discussion 69
4.1. Tide and wind conditions for floc development 69
4.2. Spring-neap variation of flocs 72
4.3. Flood-ebb variation of flocs 73
4.4. Floc structure under wind dominant condition 75
Conclusions 78
References 79
CHAPTER Ⅳ. DISTURBANCE OF SEDIMENTARY PROCESSES IN TIDAL MARSHES INVADED BY EXOTIC VEGETATION 95
Abstract 96
1. Introduction 98
2. Study area 100
3. Materials and methods 101
3.1. Measurement of bed sediment and vegetations 101
3.2. Mooring data analysis 101
3.3. Holographic image analysis 103
4. Results 104
4.1. Changes in relative bed elevation by vegetation 104
4.2. Changes in hydrodynamics by vegetation 105
4.3. Changes in flocculation by vegetation 106
5. Discussion 108
5.1. Variation in stem-induced turbulence 108
5.2. Disturbance in floc size and shape 109
5.3. Influence of vegetation on sedimentary processes in tidal salt marsh 110
Conclusions 113
References 115
CHAPTER Ⅴ. CONCLUSIONS AND SUMMARY 132
Appendices 137
APPENDIX A. PRACTICAL METHOD TO SCREEN CONTAMINATED HOLOGRAMS OF FLOCS USING LIGHT INTENSITY 137
Abstract 138
1. Introduction 139
2. Study sites and data collection 140
3. Materials and methods: LISST-HOLO 141
4. Results and discussion 144
Conclusions 150
References 151
APPENDIX B. MEASUREMENT OF SUSPENDED FLOCS USING IMAGING SYSTEMS 166
1. VIMS underwater camera system 167
2. FlocARAZI 171
References 175
Chapter Ⅰ 9
Table 1.1. Definition of used terms. 27
Chapter Ⅱ 9
Table 2.1. Notation of used terms. 53
Chapter Ⅲ 9
Table 3.1. Floc size and local condition in other locations 85
Chapter Ⅳ 9
Table 4.1. Description of vegetation and surface sediments at bare flat (Mbare) and salt marsh (Mvege).[이미지참조] 122
Appendix A. 9
Table A.1. Summary on hydrodynamics and sediment properties for Ganghwa Tidal Flat (GTF) and Geum River Estuary (GRE). 157
Table A.2. Maximum theoretical suspended sediment concentration (SSC) as a function of particle size and sample path length (L) of LISST-Holo. The gray-shaded column indicates L used for this study. 158
Appendix B. 9
Table B1. Details of floc camera: VIMS underwater camera system and FlocARAZI 177
Table B1.1. Pin number used to capture floc image 178
Table B1.2. Tank experiment design 179
Chapter Ⅰ 10
Figure 1.1. Conceptual diagram describing complex sedimentary processes (erosion, flocculation, and deposition) in intertidal flat and salt marsh. 26
Chapter Ⅱ 10
Figure 2.1. Maps of the study area in (a) Asan Bay with (b) intertidal flat. The yellow triangle in (b) denotes the location of mooring and sediment core sampling (36º 53'... 54
Figure 2.2. Schematic diagram explaining detail sequences for selecting in-situ erosion parameters: (a) τcw_b : τcw before sediment sampling for erosion experiments....[이미지참조] 55
Figure 2.3. Timeseries of meteorological and hydrodynamic data: (a) along-channel velocity (u) and water level (h) marked with time of sediment sampling for erosion... 56
Figure 2.4. Details of tidal cycles with a relative hour to high tide: (a) water level (h), (b) along-channel current velocity (u), (c) wind speed, (d) total suspended sediment... 57
Figure 2.5. Response of SSC T to (a) along-channel current velocity (u) and (b) bed shear stress (τcw) generated by current-wave interactions. The color of dots indicates...[이미지참조] 58
Figure 2.6. Erosion parameters by GEMS with stepwise increasing applied bed shear stress (τb): (a) suspended sediment concentration by bed erosion (SSCE) with...[이미지참조] 59
Figure 2.7. Temporal variations of (a) cumulative eroded mass (m) by GEMS, (b) sediment flux (black vertical bar) and cumulative sediment flux (solid red line), and... 60
Figure 2.8. Relationship between τcw after sediment sampling for erosion experiments (τcw_a) and (a) erosion rate (E), (b) erosion rate coefficient (M), (c)...[이미지참조] 61
Figure 2.9. Relationship between bed shear stress (τcw) by current-wave interactions and relative bed elevation with one standard deviation.[이미지참조] 62
Chapter Ⅲ 11
Figure 3.1. Map of study area in (a) Asan Bay with (b) intertidal flat. Yellow triangle in (b) indicates mooring station with direction of along- (u) and across- (v) channel... 86
Figure 3.2. Particle size distribution of bed sediments in Asan intertidal flats. 87
Figure 3.3. Temporal variation of (a) along-channel current velocity (u), (b) ratio of significant wave height to water level (Hs /h) with significant wave height (Hs), (c)...[이미지참조] 88
Figure 3.4. (a) Progressive vector of current at each tidal cycle. Variations of (b) water level (h), (c) along-channel current velocity (u), and (d) suspended sediment... 89
Figure 3.5. Relationship of mean floc size (davg, µm) with (a) suspended sediment concentration (SSC, mg l⁻¹) and (b) bed shear stress (τcw, Pa) induced by current-...[이미지참조] 90
Figure 3.6. Timeseries of mean floc size (davg, µm) and suspended sediment concentration (SSC, mg l⁻¹) at early flood tides.[이미지참조] 91
Figure 3.7. Under weak (left) and strong (right) wind conditions, intertidal variations in (a, g) mean floc size (davg, µm), (b, h) dimensionless floc size (d*), (c, i) current...[이미지참조] 92
Figure 3.8. Details of tidal cycles during (a) spring and (b) neap tides. Effects of winds on current velocity, bed shear stress (τcw) induced by current-wave interactions,...[이미지참조] 93
Figure 3.9. Relationship between effective density (ρe) and mean floc size (davg) during (a) flood and (b) ebb tides. The colors of markers indicate the ratio of...[이미지참조] 94
Chapter Ⅳ 12
Figure 4.1. Map of the study area (red square in the inset) in Ganghwa Island, Korea. Intertidal flats (yellowish area) are extended up to 6 km from coastal lines. The gray... 123
Figure 4.2. (a) Photograph of H-frame moorings installed at two different sites. Conceptual diagrams of mooring package at (b) Mbare and (c) Mvege.[이미지참조] 124
Figure 4.3. (a) Growth of Spartina and (b) change in the relative bed elevation at Mbare and Mvege. The shaded areas in blue and gray represent the precipitation and...[이미지참조] 125
Figure 4.4. Time series of mooring data (October 13 to 20 and November 23 to 29, 2019): (a) wind velocity, (b) tidal height, (c, d) current velocity at Mbare and Mvege,...[이미지참조] 126
Figure 4.5. Relationships between current velocity and (a) tidal height and (b) wind speed. The circles and triangles indicate Mbare and Mvege, respectively. The colors...[이미지참조] 127
Figure 4.6. Temporal variation in (a) TKE, (b) SSC, and (c) d₅₀ at Mbare (circles filled with gray) and Mvege during the inundation time. The horizontal lines indicate the...[이미지참조] 128
Figure 4.7. Relationship between TKE and current velocity at (a) Mbare and (b) Mvege.[이미지참조] 129
Figure 4.8. (a) Variation in fractal dimension (DFp) with respect to regimes at Mvege, and (b) flocs (A to F) with different shapes and sizes captured by LISST-Holo. The...[이미지참조] 130
Figure 4.9. (a) Relationship between particle size (d₅₀) and settling velocity (Ws) and (b) Shields parameter under the three regimes. The vertical lines represent the...[이미지참조] 131
Appendix A. 13
Figure A.1. (A) Satellite image showing the study area in Korean Peninsula: (B) Ganghwa Tidal Flat (GTF) and (C) Geum River Estuary (GRE). Sampling stations... 159
Figure A.2. Conceptual flow chart for hologram image analysis (modified after Many et al., 2019). Light intensity (LI) normalized on a gray scale of 0 (black) to 255... 160
Figure A.3. Variations in median particle size (d₅₀) by (A) suspended sediment concentration (SSC) and (B) light intensity (LI). 161
Figure A.4. Representative holograms (left) and montages of reconstructed images (right) with different LIs. Cyan crosses on the hologram denote the centroids of... 162
Figure A.5. Changes in the number of particles under the various LI conditions. 163
Figure A.6. Particle size distribution (PSD) at (A) GTF (circles) and (B) GRE (triangles) under various LI conditions. (C) Relationship between perimeter and area... 164
Figure A.7. (A) Perimeter-based fractal dimension (DFp) and (B) settling velocity (Ws) determined by the particle size. Note that the Ws derived from the contaminated...[이미지참조] 165
Appendix B. 14
Figure B1.1. VIMS underwater camera system 180
Figure B1.2. (a) Blueprint diagram of VIMS underwater floc camera and (b) photograph of microcontroller 181
Figure B1.3. (a) Raw floc images captured by VIMS underwater camera system. (b) Procedure for measuring flocs in image (top) and floc size distribution derived from... 182
Figure B1.4. Microcontroller scripts for (a) single and (b) continuous shooting modes. For continuous shooting mode, the time between On and Off of "image... 183
Figure B1.5. Electronic current required for camera power-on (0.41-0.55 A), single shooting (0.63-0.88 A), and continuous shooting (1.0-1.1 A). 184
Figure B2.1. Photographs of FlocARAZI 185
Figure B2.2. Tank experiment using floc camera with thin sample volume. The LED was installed inside the tank with a distance of less than 1 mm from the wall. 186
Figure B2.3. Procedure for measuring flocs in image (left). Temporal variation of median grain size (d₅₀) during tank experiments: (a) Humic acid (HA), Xanthan gum... 187