Definition of the gridsDefinition of the grids

Model Definition grid 540 (435x175)Model Definition grid 540 (435x175)

165°40 'E 166°00 'E 166°20 'E 166°40 'E 167°00 'E 167°20 'E 167°40 'E

22°50 'S

22°30 'S

22°10 'S

21°50 'S

W eather station

AD C P C urrentm eterTidegaugeD rifter

167°00 'E

Model Definition grid 180 (200x180)

Phase of ValidationPhase of Validation

0,3

0,35

0,4

0,45

T158 T229 T21 T22 T421 T24 T90

Am

plitu

de (m

)

195

200

205

210

215

220

225

230

235

240

Pha

se (°

g)

Amplitude (données)Amplitude (modèle)Phase (données)Phase (modèle)

0.395

0.40

00.370

0.360

0.350

0.345

0.340

0.340

0.330

0.325

0.330

165°40'E 166°00'E 166°20'E 166°40'E 167°00'E 167°20'E 167°40'E

22°50'S

22°30'S

22°10'S

21°50'S

1 cm 1 cm

Marégraphe < MARS3D Marégraphe > MARS3D

0.32

0.37

0.41

Validation Tide sea surface elevationValidation Tide sea surface elevation

Validation sea surface elevationValidation sea surface elevation

Validation Total currentsValidation Total currents

Validation Total currentsValidation Total currents

Drifter comparison

Drifter : velocity comparison

Examples of resultsExamples of results

1. Current evolution1. Current evolution

2. Residence times2. Residence times

Lagrangian TracorsLagrangian Tracors

Simulation without tide

Evolution of the concentration in 1 point

(example)

0.

0.1

0.2

0.3

0.5

0.6

0.7

0.8

0.9

1.0

0 10 20 30 40 50 60 70 80 90

locale-flushing time

1/e

Flushing lagconcentration evolutionthreshold passing exponential regression fitting the threshold passing curve

Con

cen

trati

on

Time elapsed (days)

0.95

e-flushing time2. Residence times2. Residence times

Method: concentration of one tracer

Case : trade wind de 8 m/s + marée

166°20'E 166°30'E 166°40'E

22°20'S

(days)

> 60

30 - 35

10 - 15

< 0.2

1 - 2

5 - 6

Jouon, Douillet, Ouillon & Fraunié, 2006, Continental Shelf Research, 26, 1395-1415

2. Residence times2. Residence times

3. Dissolved transport3. Dissolved transportTideTideBottomBottom

3. Dissolved transport3. Dissolved transportTideTideSurfaceSurface

3. Dissolved transport3. Dissolved transportTrade WTrade WBottomBottom

3. Dissolved transport3. Dissolved transportTideTideBottomBottom

Mathematical modelGeneral equation of suspended particle transport

4

zCK

3

yC +

xCK =

2

zCsWw +

1

yvC +

xuC +

tC

2z

2

2

2

2h

C : Suspended Sediment Concentration of a given grain size / population u, v, w : water velocity provided by the hydrodynamic model Kh : horizontal diffusivity Kz : vertical diffusivity from kinematic turbulent viscosity

Open boundary conditions

Surface boundary conditions 0surface

CsWzCzK

In

Out 0nC

givenC

4. Particle Dynamics4. Particle Dynamics

4. Particle Dynamics4. Particle Dynamics

cd, ce : critical shear stresses for deposition and erosionke : erosion rate coefficient

Mathematical model : cohesive particles (Mud)Fall velocity (Ds < 100 m) :

Stokes’ formula 2

ss D g 1s181W

where

water

particles

Bottom boundary condition EDbottom

Cs

Wz

Cz

K

where : shear stress provided by hydrodynamic modelling

Deposition (Krone, 1962)

Erosion (Parthéniades, 1965)

cdcd

s when CWD

1

cd when 0D

ce when 0E

cd, ce : critical shear stresses for deposition and erosionke : erosion rate coefficient

cece

e n whe kE

1

Application to the southwest lagoon of New Caledonia : Particle Diameter

20151050 km

22°20'S

22°30'S

166°25'E 166°45'E

Coral Sea

166°15'E

NEW CALEDONIA

Grey sand bottoms

White sand bottoms

Muddy bottomsN

OU

MEA

3 coarse kinds of sea bottom (Chardy et al., 1988)

100101 1000

7 m

40 m

Ex: Dumbea Bay

4. Particle Dynamics4. Particle Dynamics

4. Particle Dynamics4. Particle DynamicsApplication to the southwest lagoon of New Caledonia: Calibration

101

100

10-1

10-2

10-3

10-4

0 20 40 60 80 100

max

moy

Pourcentage de vase

(P

a)

0.017

Estimate of a global critical shear stress under tide + trade wind forcings

% of mud

averaged

Example : Deposition after one tidal cycle

166°10'E 166°20'E 166°30'E 166°40'E

22°20'S

22°30'S0.5

0.0

1.0

Deposition

166°10'E 166°20'E 166°30'E 166°40'E

22°20'S

22°30'S

90%

90%

70%

50%

40%

30%

20%

10%

5%

70%

50%

40%

30%

20%

10%

5%

-

-

-

-

-

-

-

<

>

SIMULATIONTide + Trade wind 8 m/s Percentage of mud

Reference : Douillet, Ouillon & Cordier, 2001, Coral Reefs, 20, 361-372

4. Particle Dynamics4. Particle Dynamics

4. Particle Dynamics4. Particle Dynamics