Predictability of Seabed Change due to UnderwaPredictability of Seabed Change due to Underwater Sand Mining in Coastal Waters of Korter Sand Mining in Coastal Waters of Koreaea

Chang S. Kim, Hak Soo Lim and Jinah KimChang S. Kim, Hak Soo Lim and Jinah Kim

Korea Ocean R&D InstituteKorea Ocean R&D InstituteCoastal Engineering DivisionCoastal Engineering Division

1270 Sa2Dong Ansan 426-744 South Korea.1270 Sa2Dong Ansan 426-744 South Korea.

surfkim@kordi.re.krsurfkim@kordi.re.kr

2006ROMS/TOMS Europe Nov 6-8, 2006

Alcala De Henares Spain

AbstractAbstract Numerical modeling and field experiment have been conducted to predict the seabed change due to underwater sand mining in coastal waters of Korea. The macro-tidal Kyunggi Bay is approximately 20,000 km2, where underwater sand has been extracted approximately more than 20 million m3 annually. Suspended sediment (SS) transport in the water column and sea bed has been a critically important issue to many concerns. In this study, we present the numerical prediction of sediment transport processes such as SS dispersion and consequent change in sediment types in sea bottom. We use full 3-D model ROMS to implement the sediment dynamics by adopting the extensively observed field data associated with modeling inputs and model validation.

Seabed Sand Mining Area Seabed Sand Mining Area in Kyunggi Bay, Koreain Kyunggi Bay, Korea

(Songap)선갑(Pungdo)풍도 (Kukwado)국화도(Paega)백아

(Kurop)굴업 (Tokchok)덕적 (Yonghung)영흥

(Yigok)이곡

8 8

44

66

77

11

22

33

55

99

283858688898283858688898

243454648494243454648494

263656668696263656668696

273757678797273757678797

103040607090103040607090

21315161819121

3151618191

223252628292223252628292

233353638393233353638393

253555658595253555658595

293959698999293959698999

48 7878 184818

72 72

71

80 80

77 77

76 76

74 74

7373

7575

7979

14441444

16461646

17471747

20502050

114111

4112421242

13431343

15451545

19491949

148 118128148118128

114124144114124144

116126146116126146

117127147117127147

100120130150100120130150

111121141111121141

112122142112122142

113123143113123143

115125145115125145

119129149119129149

138 108138108

104134104134

106136106136

107137107137

110140110140

101131101131

102132102132

103133103133

105135105135

109139109139

3 333

2222

4444

9999

1111

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6666

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8888

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43 33433343334333

3242324232423242

3444344434443444

3949394939493949

3141314131413141

3242324232423242

3545354535453545

3747374737473747

3949394939493949

3141314131413141

3343334333433343

3545354535453545

3646364636463646

3747374737473747

3848384838483848

4050405040504050

3444344434443444

3646364636463646

3848384838483848

4050405040504050

1323637383132363738313236373831323637383 5393539353935393

15

1222627282122262728212226272821222627282

1424647484142464748414246474841424647484

1929697989192969798919296979891929697989

1121617181112161718111216171811121617181

1222627282122262728212226272821222627282

1525657585152565758515256575851525657585

17276777871727677787172767778717276777

19

16

296979891929

60 60 60 60

98 58 98 58 98 58 98 58

96 56 96 56 96 56 96 56

94 54 94 54 94 54 94 54

60 60 60 60

98 58 98 58 98 58 98 58

97 57 97 57 97 57 97 57

96 56 96 56 96 56 96 56

95 55 95 55 95 55 95 55

93 53 93 53 93 53 93 53

91 51 91 51 91 51 91 51

99 59 99 59 99 59 99 59

97 57 97 57 97 57 97 57

95 55 95 55 95 55 95 55

92 52 92 52 92 52 92 52

91 51 91 51 91 51 91 51

99 59 99 59 99 59 99 59

94 54 94 54 94 54 94 54

92 52 92 52 92 52 92 52

90 80 70 30 20 10 90 80 70 30 20 10 90 80 70 30 20 10 90 80 70 30 20 10

88 78 68 28 18 88 78 68 28 18 88 78 68 28 18 88 78 68 28 18

86 76 66 26

69

86 76 66 26 16 86 76 66 26 16 86 76 66 26 16

84 74 64 24 14 84 74 64 24 14 84 74 64 24 14 84 74 64 24 14

90 80 70 30 20 10 90 80 70 30 20 10 90 80 70 30 20 10 90 80 70 30 20 10

88 78 68 28 18 88 78 68 28 18 88 78 68 28 18 88 78 68 28 18

87 77 67 27 17 87 77 67 27 17 87 77 67 27 17 87 77 67 27 17

86 76 66 26 16 86 76 66 26 16 86 76 66 26 16 86 76 66 26 16

85 75 65 25 15 85 75 65 25

87

85 75 65 25 15 85 75 65 25 15

83 73 63 23 13 83 73 63 23 13 83 73 63 23 13 83 73 63 23 13

81 71 61 21 11 81 71 61 21 11 81 71 61 21 11 81 71 61 21 11

89 79 69 29 19 89 79 69 29 19 89 79

123 113113113113 123123123

124

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111111111111

112112112112

115115115115

117117117117

119119119119

111111111111

113113113113

115115115115

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117117117117

118118118118

120120120120

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116116116116

118118118118

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122122122122

124124124124

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130130130130

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103133143103133143103133143103133143

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104134144104134144104134144104134144

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103133143103133143103133143103133143

105135145105135145105135145105135145

106136146106136146106136146106136146

107137147107137147107137147107137147

108138148108138148108138148108138148

110140150110140150110140150110140150

104134144104134144104134144104134144

106136146106136146106136146106136146

108138148108138148108138148108138148

110140150110140150110140150110140150

100100100100

100100100100

Depth (m)

Numerical Model Grid for Kyunggi Bay

125.4 125.6 125.8 126.0 126.2 126.4 126.6 126.8 127.0

36.8

37.0

37.2

37.4

37.6

37.8

38.0

125.4 125.6 125.8 126.0 126.2 126.4 126.6 126.8 127.0

36.8

37.0

37.2

37.4

37.6

37.8

38.0

INCHEON

TAEAN

LA

TIT

UD

E(N

)

LONGITUDE (E)

125.75 126.00 126.25 126.50

-40

-30

-20

-10

0

DE

PT

H(M

)LONGITUDE (E)

VERTICAL STRUCTURE

Curvilinear Orthogonal Grid

Terrain-Following Vertical Grid(20 arrays)

3-D Sediment Transport Equations

wzyx

s

DSD

ck

Dy

ck

yx

ck

xD

)c)ww(D(

y

)Dvc(

x

)Duc(

t

)Dc(

Variable Description

Falling Velocity

Concentration of Suspended Sediment

Hor/Ver Mixing Coefficients

Source/Sink of Sediment

Source Conc at the Sea Surface

Source Conc. at the Seabed

Deposition Rate through sinking

),,(),(),,( tyxyxHtyxD

c

zyx kkk ,,

wS

sS

sw

bS

dS

dbsw SSSS

ce

cebOb ES

)1(

222bbTbDb vuVC

c

wS sd

1, at

Erosion Rate Porosity

Velocity at seabed RMS Tidal Current

OE

,

wcb

bV T

Source Concentrations of SS in Source Concentrations of SS in Kyunggi BayKyunggi Bay

Dredging Dredging Volume /hrVolume /hr

1,0001,000 mm33/hr/hr 300,000m300,000m33//

12.5 days12.5 days

SS Flux in Over-SS Flux in Over-spilled Waterspilled Water

73.6173.61 kg/skg/s Pumping Water VolumPumping Water Volume : 10 x Loading Volue : 10 x Loading Volumeme

SS Spilled : 10% od LSS Spilled : 10% od Loading Volume (MMS, oading Volume (MMS, 1999)1999)

99%Sand: 99%Sand: Composition of Composition of Spilled SSSpilled SS

0.5:0.25:0.125:0.5:0.25:0.125:

0.0625:0.031250.0625:0.03125

mmmm

3:3:2:1:3:3:2:1:11

7950:7950:7950:7950:

5300:2650:5300:2650:

2650 mg/l2650 mg/l

98%Sand 98%Sand Composition of Composition of Spilled SSSpilled SS

0.5:0.25:0.125:0.5:0.25:0.125:

0.0625:0.031250.0625:0.03125

mmmm

2:2:2:2:2:2:2:2:22

5300:5300:5300:5300:

5300:5300:5300:5300:

5300 mg/l5300 mg/l

Volume =3,000,000 m3 / 12.5day

Ø1:Ø2:Ø3:Ø4:Ø5 = 2:2:2:2:2

SS Dispersion (Started during Spring Tide)SS Dispersion (Started during Spring Tide)

BottomBottom

SurfaceSurface

Volume =3,000,000 m3 / 12.5day

Ø1:Ø2:Ø3:Ø4:Ø5 = 2:2:2:2:2

SS Dispersion (Started During Neap Tide)SS Dispersion (Started During Neap Tide)

BottomBottom

SurfaceSurface

126.22 126.23 126.24 126.2537.09

37.10

37.11

37.12

LA

TIT

UD

E(N

)

LONGITUDE (E)

2001.10.12 16:00

BC

A

505

SURFACE

126.22 126.23 126.24 126.2537.09

37.10

37.11

37.12

LA

TIT

UD

E(N

)

LONGITUDE (E)

2001.10.12 18:00

BC

A5

5

SURFACE

126.22 126.23 126.24 126.2537.09

37.10

37.11

37.12

LA

TIT

UD

E(N

)

LONGITUDE (E)

2001.10.12 20:00

BC

A

5

5

SURFACE

5

126.22 126.23 126.24 126.2537.09

37.10

37.11

37.12

LA

TIT

UD

E(N

)

LONGITUDE (E)

2001.10.12 14:00 ~16:00

A

BC

4.3mg/l

89.0mg/l

: Barge C

9.5mg/l4.6mg/l

16.1mg/l

A

6.9mg/l

CB

: Barge A: Barge B

4.2mg/l

48.3mg/l

7.3mg/l

7.0mg/l

Field Experiment conducted between 14:00 -16:00 on October 12, 2001 in Kyunggi Bay.

Model Validation with Field Observed DataModel Validation with Field Observed Data (2,000 m (2,000 m3 3 3 3 Barges )Barges )

Vertical Profiles of SS Concentration Observed and Simulated for 14:00-16:00 on October12, 2001 in Kyunggi Bay.

Comparison of Model Results and Field Comparison of Model Results and Field Observed DataObserved Data

Tidal current of 0.5 m/s Extractuin Volume 300,000 m3

15 20 25 30 355

10

15

X (km)

Y (km)

SS (mg/l)

BOTTOMTidal Current = 0.5 m/sQ = 300,000 m /12.5daysD + 1

3v

5

1Ø3

+

15 20 25 30 355

10

15

X (km)

Y (km)

SS (mg/l)

BOTTOMTidal Current = 0.5 m/sQ = 300,000 m /12.5daysD + 1

3v

51

1

15

1

Ø4

+

15 20 25 30 355

10

15

X (km)

Y (km)

SS (mg/l)

BOTTOMTidal Current = 0.5 m/sQ = 300,000 m /12.5daysD + 1

3v

1

Ø5

+

15 20 25 30 355

10

15

1 2 3 4 5

X (km)

Y (km)

SS (mg/l)

BOTTOMTidal Current = 0.5 m/sQ = 300,000 m /12.5daysD + 1

3v

∑Ø

+

SS Redistribution at Seabed Based on Particle Size SS Redistribution at Seabed Based on Particle Size (Model Results)(Model Results)

ConclusionsConclusions In this study, a numerical approach using the fully 3-D model ROMS In this study, a numerical approach using the fully 3-D model ROMS

has been conducted to investigate the sediment dynamics arising has been conducted to investigate the sediment dynamics arising from the undersea sand mining operation. Fundamental parameters from the undersea sand mining operation. Fundamental parameters required for model implementation have been obtained through required for model implementation have been obtained through extensive field experiments done in Kyunggi Bay in Korea. extensive field experiments done in Kyunggi Bay in Korea.

The estimation of sediment source concentration adapted in this The estimation of sediment source concentration adapted in this study might be very useful for application to other site-specific area. study might be very useful for application to other site-specific area.

The bottom sediment composition is very important to predict the The bottom sediment composition is very important to predict the habit change at the seabed. Three-dimensional evolution of habit change at the seabed. Three-dimensional evolution of sediment transport shows a variety of dependent parameters on sediment transport shows a variety of dependent parameters on environmental impacts, particularly on the geologic change in environmental impacts, particularly on the geologic change in benthic habitat. benthic habitat.