First steps in the implementation of a First steps in the implementation of a sediment transport model in the Ebro Delta sediment transport model in the Ebro Delta

Continental Shelf (Catalan Sea)Continental Shelf (Catalan Sea)

UPC - LIM - Juan Fernandez, Manuel Espino, Vicenç Gracia,

Gabriel Jordà, Agustin Sanchez-Arcilla

Objectives of the PresentationObjectives of the Presentation

S7.3.1 Data: Inventory of needs and availability – Ebro Delta Continental Shelf

S7.3.2 Sedimentary modelling - Ebro Delta Continental Shelf

Description of work carried out Data gathering process First model implementations Future work

Revision of State of the Art Formulation for Sediment Transport Modelling outside the Surf Zone (D7.3.2.2). Input from several partners. Almost completed.

Field Site AreaField Site Area

Ebro Delta Continental Shelf

West Mediterranean Sea

135 km south of Barcelona

Ebro shelf in transition zone

Figure 1 – Ebro Delta location (Durand et al. 2002)

Oceanographic Characteristics - Oceanographic Characteristics - Driving termsDriving terms

Ebro Continental shelf is becoming more wave dominated

Water level increase can shift this.

Figure 2 - Delta classification as a function of dominant dynamical processes (Sanchez-Arcilla and Jimenez, 1997)

Oceanographic Characteristics - Oceanographic Characteristics - Driving termsDriving terms

Ebro River– Highest water discharge rates and biggest

hydrological catchment in the Iberian peninsula – Highly regulated watercourse (dams)

Ebro River Discharge

0.00E+00

5.00E+02

1.00E+03

1.50E+03

2.00E+03

2.50E+03

3.00E+03

3.50E+03

28/06/1980 25/03/1983 19/12/1985 14/09/1988 11/06/1991 07/03/1994 01/12/1996 Time

Dis

char

ge

(cu

mec

s)

Figure 3 – Ebro Daily Discharge at Tortosa (FANS project)

Oceanographic Characteristics - Oceanographic Characteristics - Driving termsDriving terms

Waves– Most energetic forcing agent acting in

the coastal zone– ‘Energetic’ period, from October till

March– Most persistent waves are from eastern

(25%) and southeastern (20%) directions.

– Wave periods range between 2 and 10 s and heights are lower than 4.0m for 98% of the time.

– Storm waves - significant wave height exceeds 1.5 m

Figure 4 – Directional distribution of waves at Cap Tortosa (Jiménez, 1996).

Oceanographic Characteristics - Oceanographic Characteristics - Driving termsDriving terms

Tides – Mean water level– Semidiurnal micro-tide area– Maximum tidal range of around 0.25m– Water level changes due to meteorological

effects can be in excess of 0.5m. – Meteorological tide is relatively frequent in the

study area.– These events can occur simultaneously

Oceanographic Characteristics - Oceanographic Characteristics - Driving termsDriving terms

Currents– Wind main physical forcing– Southerly and south-westerly wind prevail

during summer and northwest winds during winter

– Northern current

Bottom Sediment CharacterisationBottom Sediment Characterisation

Inner zone (from the beach to 7m), medium and small size sands, diameter no greater than 125 µm.

Mid-zone (7m to 10-15m) smaller sands diameters from 63 to 125 µm.

Mud belt. Offshore, surface sediment

consists of relict transgressive sand

Figure 5 – Distribution of sediment types (Diaz et al, 1990)

Bottom Sediment CharacterisationBottom Sediment Characterisation

Figure 6 – Ebro Delta Continental Shelf bathymetry and grain size

A grain size distribution map is being constructed for the following grain classes and their corresponding D50:

– I clay: 2µm – II silt: 15µm – III fine sands: 75µm– IV coarser sands:125µm– V cohesive sediments: 140µm

Grain size DistributionGrain size Distribution Several sources have already been consulted:

– Core survey information from several locations (Guillén et al. 2005).

– Percentage maps for sands, silts and clays (Callis et al. 1988)

– Percentage maps for particles greater than 40µm (Callis et al. 1988)

– Mean grain size maps for the whole Ebro

continental shelf.

Figure 7 – Spatial percentage distribution for Clay(Callis et al. 1988)

Figure 9 – Spatial percentage distribution for particles greater than 40µm (Callis et al. 1988)

Figure 8 – Cross-shore profile and mean grain sizeof bottom sediment (Guillén et al. 2005)

SymphonieSymphonie

Developed in the Pole d’Oceanographie Cotiere in Toulouse (France) http://poc.obs-mip.fr/

3D primitive equation model of the coastal ocean. Hybrid vertical coordinates sigma-z Full air-sea interactions Implemented and validated in different coastal and

ROFI areas

http://poc.obs-mip.fr/pages/research_topics/modelling/symphonie/symphonie.htm

STRADA (Simulations du TRAnsport par Diffusion Advection).

Settling velocity: (after Ulses et al. (2007)) the Stoke’s Law or Zanke formula for non-cohesive and Agrawal and Pottsmith for aggregates

– Stoke’s Law

– Zanke (1977)

– Agrawal and Pottsmith (2000)

FormulationFormulation

2)(18

1gDw ss

1)1( 5.02*

** S

SW

17.131045.0)( adws

gdsd

S )1(4*

Bottom shear stress. Current and waves. After Soulsby et al. (1993).

– Current

– Waves

Possibility of bed armouring: following Harris and Wiberg (2001).Thickness of active layer:

– Sandy beds (bed-form)

– Silty beds

FormulationFormulation

50)( 6

2D

C

TQ

ripb

bavbripmix

llcrslb gfrQ 5.1)(max

1 )()((0.8

50)50(max)( 6)(8 Dcr

siltmix

25.0 bDc VC

25.0 orbww Uf )sinh(

5

khT

HUorb

19.0)/(21.5exp00251.0 nw kAf

3.0wf

57.1/ nkA

57.1/ nkA

2

01 )/log(

zzCD

Erosion non-cohesive formulation: Flux – F=fwsC(z1)ρ; for C(z1), choice of– Smith and McLean (1977): semi-empirical relation for the bed concentration.

Rouse profile for , or for

where and

with a reference height of

– Zysermann and Fredsoe (1994): empirical model with a reference height of

Erosion cohesive formulation: choice of following

– Mehta:

– Partheniades: , for and otherwise.

FormulationFormulation

max

11)(

b

aa z

zczc

mb

ww z

zzczc

1

1 )()(wa zzz 1 1zzw

2max* Tu

zw m

im u

wb

max,*max,

'1

'

o

oba

cc

cr

cr

)(

' max

75.1

75.1

)(46.0

331.01

)(331.0

crs

crsac

ercr

ercrbMEE

,

,

)1)(( ,,,,tn

depcrercrdepcrercr e

1

,ercr

skeE

ercrs , 0E

Available informationAvailable information

A whole inventory of the available data necessary for the modelling stage for the Ebro Continental Shelf was carried out. – EU-MAST III – Project FANS. MAS3-CT95-

0037 (1996-1997)– TRASEDVE projects (1999 – National project)– Previous PhD reports (Gracia and Jordà)

FANSFANS

– Spatial superficial suspended sediment concentration measures were taken around the Ebro River Plume.

– Two instrumented bottom boundary layer tripods were placed at 8.5m and 12.0m measuring suspended sediment concentration at three different depths

– Two RCM07 meters coupled with transmissometers were placed at 60m and 100m depth to measure suspended sediment transport at 5m above the seabed at the mid and outer shelf.

Sediment transport measures were carried out using three different approaches in three areas

Figure 10 – EU-MAST-III Project FANS instrumented locations

FANSFANS

Data from the mentioned locations were examined

Figure 12 – EU-MAST-III Project FANS sediment transport measures location

-14

-13

-12

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1

Figure 11 – Tripods location

Event selection strategyEvent selection strategy

Events were selected depending on:– Data availability– Driving terms

River influence Waves Wind

– Significant sediment transport measured

0

200

400

600

800

1000

1200

1400

01/02/1997 06/02/1997 11/02/1997 16/02/1997 21/02/1997 26/02/1997

0

5

10

15

20

25

01/02/1997 00:00 06/02/1997 00:00 11/02/1997 00:00 16/02/1997 00:00 21/02/1997 00:00 26/02/1997 00:000

50

100

150

200

250

300

350

Event descriptionEvent description River Plume example case:

– 6-7 February 1997: supercritical river plume conditions with a high river discharge and varying wind conditions.

Figure 13 – Wind and discharge conditions during February

Figure 14 – Wind rose for the February event

Constant discharges of 880m3/s

Event descriptionEvent description Inner shelf area example case:

26 December 1996 – 3 January 1997: High discharge from the Ebro River and high wave energy.

Figure 16 – Driving terms for the first tripod event

0

1

2

3

4

5

6

7

8

9

17/12/1996 22/12/1996 27/12/1996 01/01/1997 06/01/1997 11/01/1997 16/01/1997

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1

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6

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8

9

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1

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3

4

5

6

7

8

9

Figure 15 – SSC for the three OBS sensors during the first tripod event

0

200

400

600

800

1000

1200

1400

26/12/199600:00

27/12/199600:00

28/12/199600:00

29/12/199600:00

30/12/199600:00

31/12/199600:00

01/01/199700:00

02/01/199700:00

03/01/199700:00

04/01/199700:00

05/01/199700:00

Dis

char

ge

(cu

mec

s)

34.5

35

35.5

36

36.5

37

37.5

38

38.5

Sal

init

y (p

su)

4

5

6

7

8

9

10

11

12

13

Tp

(s)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

Hm

0 (

m)

0

50

100

150

200

250

300

350

Win

d D

ir.

(deg

)

0

5

10

15

20

25

Win

d V

el.

(m/s

)

1000

1005

1010

1015

1020

1025

1030

1035

1040

A.P

r (m

b)

8.7

8.8

8.9

9

9.1

9.2

9.3

MW

L (

m)

Event descriptionEvent description

Mid and outer shelf area example case:3-9 November 1996:

significant transportation and low wave energy period

Figure 17 – Driving terms for the RCM07 events0

2

4

6

8

10

12

14

02/11/1996 00:00:00 03/11/1996 00:00:00 04/11/1996 00:00:00 05/11/1996 00:00:00 06/11/1996 00:00:00 07/11/1996 00:00:00 08/11/1996 00:00:00 09/11/1996 00:00:00

SS

C (

mg

/l)

0

5

10

15

20

25

30

35

Cu

rren

t V

elo

city

(m

/s)

0

50

100

150

200

250

300

350

Cu

rren

t D

irec

tio

n (

deg

rees

)

0

2

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8

10

12

14

16

18

20

0

50

100

150

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250

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1024

1026

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1034

1036

1038

1040

1042

v

0

0.1

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v

0

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8

v

First results – Plume EventsFirst results – Plume Events

The sediment transport model has been initially implemented around the Ebro river mouth.

POC Pole d’Oceanographie Cotiere in Toulouse collaboration.

Four plume events have been modelled and analysed.

Results have been compared to measured concentration and to satellite images (qualitative).

6-7 February 1997 simulation

Flow rates around 880m3/s

Varying wind conditions

Figure 21 – Modelling results and satellite image Landsat-TM (Channel 2, visible green) for the February simulation

First results – Plume EventsFirst results – Plume Events

Figure 20 – Wind conditions for the February event

6-16 July 1997 simulation

Flow rates from 220 to 120m3/s

Constant wind conditions

Figure 23 – Modelling results and satellite image Landsat-TM (Channel 2, visible green) for the July simulation

First results – Plume EventsFirst results – Plume Events

Figure 22 – Wind conditions for the July event

Next stepsNext steps Sediment transport modelling (V0) for the

tripods and RCM07 areas Sediment transport modelling (V0) of the

whole Ebro Delta Continental Shelf Results analysis Improvement of the sediment transport

module (V1) Target Operational Period (TOP) model