First steps of the implementation of a sediment transport model in by yurtgc548

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									  First steps in the implementation of a
sediment transport model in the Ebro Delta
     Continental Shelf (Catalan Sea)




UPC - LIM - Juan Fernandez, Manuel Espino, Vicenç Gracia,
           Gabriel Jordà, Agustin Sanchez-Arcilla
    Objectives 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 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 -
          Driving 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 -
          Driving terms
 Ebro River
  – Highest water discharge rates and biggest
    hydrological catchment in the Iberian peninsula
  – Highly regulated watercourse (dams)
           Discharge (cumecs)




                                                                            Ebro River Discharge

                                3.50E+03



                                3.00E+03



                                2.50E+03



                                2.00E+03



                                1.50E+03



                                1.00E+03



                                5.00E+02



                                0.00E+00
                                     28/06/1980   25/03/1983   19/12/1985     14/09/1988   11/06/1991   07/03/1994   01/12/1996   Time



                                                  Figure 3 – Ebro Daily Discharge at Tortosa (FANS project)
  Oceanographic Characteristics -
         Driving 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%   Figure 4 – Directional distribution of waves
    of the time.                                   at Cap Tortosa (Jiménez, 1996).

  – Storm waves - significant wave height
    exceeds 1.5 m
  Oceanographic Characteristics -
         Driving 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 -
         Driving terms
 Currents
  – Wind main physical forcing
  – Southerly and south-westerly wind prevail
    during summer and northwest winds during
    winter
  – Northern current
  Bottom 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 Characterisation
 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




                                     Figure 6 – Ebro Delta Continental Shelf bathymetry and grain size
   Grain 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
                                                  Figure 7 – Spatial percentage distribution for Clay
     40µm (Callis et al. 1988)                                   (Callis et al. 1988)

   – Mean grain size maps for the whole Ebro
     continental shelf.




                 Figure 8 – Cross-shore profile and mean grain size    Figure 9 – Spatial percentage distribution for
                      of bottom sediment (Guillén et al. 2005)        particles greater than 40µm (Callis et al. 1988)
                       Symphonie
 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
                     Formulation
 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
                                           1
   – Stoke’s Law                   ws         (  s   ) gD 2
                                          18 



                              
   – Zanke (1977)      W* 
                              S*
                                   (1  S   2 0.5
                                              *)       
                                                      1          S* 
                                                                          d
                                                                         4
                                                                               ( s  1) gd




                                                           ws (d )  0.45  10 3 a 1.17
   – Agrawal and Pottsmith (2000)
                                            Formulation
   Bottom shear stress. Current and waves. After Soulsby et al. (1993).
                                                                        2
                                                                 
     – Current       c  0.5C VD b
                                    2
                                                     log( z / z ) 
                                               CD                
                                                           1   0 


                                                              H 5                                        
                                                                                     f w  0.00251 exp 5.21( A / k n ) 0.19              A / k n  1.57
     – Waves         w  0.5 f wU   2
                                      orb        U orb 
                                                           T sinh(kh)
                                                                                     f w  0 .3               A / k n  1.57



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

     – Sandy beds (bed-form)                   mix ) 
                                                ( rip     QbTbav
                                                                    6 D50                            
                                                                                          Qb   frl 8.0((  s   ) g 1 ( m ax   cr ( l ) )1.5   
                                                          2Cb rip                                l


     – Silty beds
                                              mix )  8( max   cr(50) )  6D50
                                               ( silt
                                            Formulation
 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.
                                                           bm ax                                                                    bm
                                                z                                                                         z 
      Rouse profile                c( z1 )  ca  1
                                                z    
                                                                    for        z a  z1  z w   , or     c( z1 )  c( z w ) 1 
                                                                                                                            z            for   z w  z1
                                                 a                                                                         w
                              wi                                     u*maxT
      where    bm ax,m                    and               zw 
                           u*m ax,m                                   2

                                                                            cb  o '                   ( m ax   cr )
      with a reference height of                                    ca                           '
                                                                           1   o '                         cr


    – Zysermann and Fredsoe (1994): empirical model with a reference height of
                                                            0.331( s   cr )1.75
                                                      ca 
                                                              0.331
                                                           1       ( s   cr )1.75
                                                              0.46

 Erosion cohesive formulation: choice of following
                                 b   cr,er
    – Mehta:        E  EM                                           cr,er   cr,dep  ( cr,er   cr,dep )(1  e nt )
                                    cr,er
                                          s      
    – Partheniades:                E  ke
                                               1
                                                                    , for s   cr,er and                         E 0            otherwise.
                                          cr,er 
        Available 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)
                              FANS
 Sediment transport measures were carried out using
  three different approaches in three areas

  – 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.


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

 Data from the
  mentioned
  locations were
  examined

                                  1

                                  0

                                  -1

                                  -2

                                  -3

                                  -4

                                  -5

                                  -6

                                  -7

                                  -8

                                  -9

                                  -10

                                  -11

                                  -12

                                  -13

                                  -14




   Figure 11 – Tripods location
                                         Figure 12 – EU-MAST-III Project FANS sediment transport measures location
       Event selection strategy
 Events were selected depending on:
  – Data availability
  – Driving terms
      River influence
      Waves
      Wind
  – Significant sediment transport measured
                        Event description
 River Plume example case:
   – 6-7 February 1997: supercritical river plume conditions with a
     high river discharge and varying wind conditions.




                                                                   Figure 14 – Wind rose for the February event

                                                                   Constant discharges of 880m3/s



       Figure 13 – Wind and discharge conditions during February
                                   Event description
   Inner shelf area example case:
    26 December 1996 – 3 January 1997: High                                                           350
                                                                                                                                                                                                                 25




    discharge from the Ebro River and high wave
                                                                                                      300
                                                                                                                                                                                                                 20




                                                                                                                                                                                                                            Wind Vel. (m/s)
                                                                                    Wind Dir. (deg)
                                                                                                      250

                                                                                                                                                                                                                 15
                                                                                                      200




    energy.                                                                                           150



                                                                                                      100



                                                                                                        50
                                                                                                                                                                                                                 10




                                                                                                                                                                                                                 5




                                                                                                        0                                                                                                        0




                                                                                                      1040


                                                                                                      1035


                                                                                                      1030




                                                                                  A.Pr (mb)
                                                                                                      1025


                                                                                                      1020


                                                                                                      1015


                                                                                                      1010


                                                                                                      1005


                                                                                                      1000




                                                                                                        9.3




                                                                                                        9.2




                                                                                                        9.1




                                                                                          MWL (m)
                                                                                                         9




                                                                                                        8.9




                                                                                                        8.8




                                                                                                        8.7




                                                                                                        3. 00




                                                                                                        2. 50




                                                                                                        2. 00




                                                                                              Hm0 (m)
                                                                                                        1. 50




                                                                                                        1. 00




                                                                                                        0. 50




                                                                                                        0. 00




                                                                                                        13


                                                                                                        12


                                                                                                        11


                                                                                                        10




                                                                                           Tp(s)
                                                                                                         9


                                                                                                         8


                                                                                                         7


                                                                                                         6


                                                                                                         5


                                                                                                         4




                                                                                                        1400                                                                                                         38.5
                                                                              Discharge (cumecs)

                                                                                                        1200                                                                                                         38




                                                                                                                                                                                                                                    Salinity (psu)
                                                                                                                                                                                                                     37.5
                                                                                                        1000

                                                                                                                                                                                                                     37
                                                                                                         800
                                                                                                                                                                                                                     36.5
                                                                                                         600
                                                                                                                                                                                                                     36

                                                                                                         400
                                                                                                                                                                                                                     35.5

                                                                                                         200
                                                                                                                                                                                                                     35

                                                                                                              0                                                                                                      34.5


                                                                                              26/12/1996 27/12/1996 28/12/1996 29/12/1996 30/12/1996 31/12/1996 01/01/1997 02/01/1997 03/01/1997 04/01/1997 05/01/1997
                                                                                                00:00      00:00      00:00      00:00       00:00     00:00      00:00      00:00      00:00      00:00      00:00



    Figure 15 – SSC for the three OBS sensors during the first tripod event                                       Figure 16 – Driving terms for the first tripod event
           Event description
                                                                   35                                                                                                                                                 350


                                                                   30                                                                                                                                                 300




                                                                                                                                                                                                                             Current Direction (degrees)
                                                                   25                                                                                                                                                 250




 Mid and outer shelf




                                          Current Velocity (m/s)
                                                                   20                                                                                                                                                 200


                                                                   15                                                                                                                                                 150


                                                                   10                                                                                                                                                 100


                                                                   5                                                                                                                                                  50


                                                                   0                                                                                                                                                  0




  area example case:
  3-9 November 1996:
    significant
    transportation and low
    wave energy period


                                                                    14



                                                                    12



                                                                    10



                                                                        8
                             SSC (mg/l)




                                                                        6



                                                                        4



                                                                        2



                                                        0
                                                 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




                                                           Figure 17 – Driving terms for the RCM07 events
    First 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).
     First results – Plume Events
 6-7 February 1997 simulation
  Flow rates around 880m3/s
  Varying wind conditions
                                                                                        Figure 20 – Wind conditions for the February event




     Figure 21 – Modelling results and satellite image Landsat-TM (Channel 2, visible green) for the February simulation
    First results – Plume Events
 6-16 July 1997 simulation
  Flow rates from 220 to 120m3/s
  Constant wind conditions
                                                                                           Figure 22 – Wind conditions for the July event




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

								
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