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

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.

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

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  1. 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

  2. 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.

  3. 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)

  4. 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)

  5. Oceanographic Characteristics - Driving terms • Ebro River • Highest water discharge rates and biggest hydrological catchment in the Iberian peninsula • Highly regulated watercourse (dams) Figure 3 – Ebro Daily Discharge at Tortosa (FANS project)

  6. 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% of the time. • Storm waves - significant wave height exceeds 1.5 m Figure 4 – Directional distribution of waves at Cap Tortosa (Jiménez, 1996).

  7. 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

  8. Oceanographic Characteristics - Driving terms • Currents • Wind main physical forcing • Southerly and south-westerly wind prevail during summer and northwest winds during winter • Northern current

  9. 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)

  10. 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

  11. 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 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 8 – Cross-shore profile and mean grain size of bottom sediment (Guillén et al. 2005) Figure 9 – Spatial percentage distribution for particles greater than 40µm (Callis et al. 1988)

  12. 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

  13. 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 • Stoke’s Law • Zanke (1977) • Agrawal and Pottsmith (2000)

  14. Formulation • 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

  15. 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. 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.

  16. 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)

  17. 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

  18. FANS • Data from the mentioned locations were examined Figure 11 – Tripods location Figure 12 – EU-MAST-III Project FANS sediment transport measures location

  19. Event selection strategy • Events were selected depending on: • Data availability • Driving terms • River influence • Waves • Wind • Significant sediment transport measured

  20. 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

  21. Event description • Inner shelf area example case: 26 December 1996 – 3 January 1997: High discharge from the Ebro River and high wave energy. Figure 15 – SSC for the three OBS sensors during the first tripod event Figure 16 – Driving terms for the first tripod event

  22. Event 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 events

  23. 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).

  24. 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

  25. 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

  26. 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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