1. Modellierung von Sedimenttransporten im Wattenmeer - Gerold Brink-Spalink - Forschergruppe BioGeoChemie des Watts TP 4 Gerold Brink-Spalink Jörg-Olaf Wolff Emil Stanev BioGeoChemistry of Tidal Flats (SP 4) Modelling Mud and Sand Transport in the East-Frisian Wadden Sea

2. Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions

3. Study Area: Spiekeroog Island Spiekeroog Otzumer Balje

4. Model Area: East Frisian Wadden Sea 7 Basins Volume High Water: 184 Mio m³ Volume Low Water: 39 Mio m³ Area: 71 Mio m² Inlet width: 2500 m Inlet area: 11000 m² Spiekeroog Basin: (spring tide) Maximum channel depth: 12 m

5. Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions

6. Hydrodynamic Model (GETM) Momentum equations: Vertical mixing: k and  from k-  -turbulence-model Drying:

7. 3D-model horizontal resolution: 200 m vertical resolution: D/10 (D=water depth) vertical grid:  -coordinates Time discretization: mode splitting  t 1 =3s for sea level, vert. integr. Velocities  t 2 =15s for 3D-fields: turbulent variables,...) Hydrodynamic Model

8. Sediment Transport Model Deposition: Erosion: Settling velocity:or (Sand) (Mud)

9. Sediment on ground (Sand: 100µm, Mud) unlimited Morphologic changes during model run are not considered in topography data Water flowing into model area carries no sediment Sediment flowing out of model area is „lost“ Sediment model is initialized half a tide after hydrodynamic model Forcing on northern boundary: Boundary conditions:

10. Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions

11. Mean bottom shear velocity Maximum bottom shear velocity Duration of erosion of mud (top) and sand (bottom) during one spring tide cycle in percent: u*=1,4 cm/s u*=2,0 cm/s Hydrodynamic conditions for erosion

12. flood high water ebb low water Integrated suspended sediment concentration

15. Sediment movements after 3 tidal cycles

16. Model estimate of sediment types: Measurement of sand content in sediment: 250-125 µm125-63 µm

17. Time evolution of vertical concentration profiles

18. Vertical average of concentration:Transport through inlet: Measured concentration:

19. Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions Overview: 1.Model Area: East Frisian Wadden Sea 2.Sediment Transport Model 3.Model Results 4.Conclusions

20. A 3D-model for sediment transport has been set up, that accounts for the main processes (erosion, settling, deposition, advection, turbulent mixing) Suspended sediment concentration patterns show consistent behaviour with observations Spatial distribution of sediment types matches observations in large areas Further calibration with measurements necessary Waves need to be taken into account Conclusions: