Ocean Science www.ocean-sci.net 1812-0784 1812-0792 3 1 2007 10.5194/os-3-91-2007 http://www.ocean-sci.net/3/91/2007/ http://www.ocean-sci.net/3/91/2007/os-3-91-2007.html http://www.ocean-sci.net/3/91/2007/os-3-91-2007.pdf 91 104 2007-02-13 Modelling the cohesive sediment transport in the marine environment: the case of Thermaikos Gulf Y. N. Krestenitis K. D. Kombiadou kobiadou@civil.auth.gr Y. G. Savvidis Laboratory of Maritime Engineering and Maritime Works, Division of Hydraulics and Environmental Engineering, Department of Civil Engineering, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Greece Department of Fisheries & Aquaculture Technology, Alexander Technological Educational Institute of Thessaloniki, 632 00, Nea Moudania, Halkidiki, Greece The transport of fine-grained sediments in the marine environment entails risks of pollutant intrusions from substances absorbed onto the cohesive flocks' surface, gradually released to the aquatic field. These substances include nutrients such as nitrate, phosphate and silicate compounds from drainage from fertilization of adjacent cultivated areas that enter the coastal areas through rivers and streams, or trace metals as remainders from urban and industrial activities. As a consequence, knowledge on the motion and distribution of sediment particles coming from a given pollutant source is expected to provide the 'bulk' information on pollutant distribution, necessary for determining the region of influence of the source and to estimate probable trophic levels of the seawater and potential environmental risks. In that aim a numerical model has been developed to predict the fate of the sediments introduced to the marine environment from different pollution sources, such as river outflows, erosion of the seabed, aeolian transported material and drainage systems. The proposed three-dimensional mathematical model is based on the particle tracking method, according to which matter concentration is expressed by particles, each representing a particular amount of sedimentary mass, passively advected and dispersed by the currents. The processes affecting characteristics and propagation of sedimentary material in the marine environment, incorporated in the parameterization, apart from advection and dispersion, include cohesive sediment and near-bed processes. The movement of the particles along with variations in sedimentary characteristics and state, carried by each particle as personal information, are traced with time. Specifically, concerning transport processes, the local seawater velocity and the particle's settling control advection, whereas the random Brownian motion due to turbulence simulates turbulent diffusion. The vertical stratification of the water-column is taken into consideration by appropriate damping of the vertical diffusion term. Variations in cohesive sediment properties during the abidance in the aquatic environment include coagulation and flock break-up processes, quantification of the effects of ambient density to the density of the cohesive aggregate and the associated alterations to the falling speed of the particle. In the vicinity of the seabed, particles may deposit and gradually consolidate with time, the particles remain settled onto the bed, re-enter the flow at a later temporal point or may enter the water column for the first time, originating from the erosion of the bed. The occurrence of each of the aforementioned near-bed processes is defined according to the prevailing benthic shear stress conditions. The mathematical model has been applied to the Thermaikos Gulf, an area of high environmental and socioeconomic importance but also a region of significant pollutant forcing from various anthropogenic activities taking place in the adjoining land. Various kinds of outputs can be extracted, such as trajectories of the overall movement of specific particles and related alterations of their characteristics with time, snapshots of the domain with respect to suspended or deposited matter and natural concentrations of sediments at every required temporal and spatial point. Indicative results from yearly and monthly simulations, using input baroclinic circulation data from the North Aegean Sea model and river discharges are presented and discussed, including outputs from a Typical One-Year Simulation (TOYS), the simulation of the period from 3 September 2001 to 31 August 2002 (S1A2) and the January 2003 experiment (J03). The description of the processes that have been incorporated in the parameterization covers the most significant factors controlling transport and mixing of fine grained sediments in the marine environment, thus validating the accuracy and completeness of the model. One of the major advantages, apart from the observation of the phenomena in scales smaller than the grid size, describing the natural processes more accurately, is the flexibility in accepting various pollutant sources and the applicability to different domains with minor modifications. The model has been incorporated in the MFSTEP project, as part of the developed operational forecasting system for the Mediterranean Sea. The application can be used for the prognosis of the seawater quality for current and for future conditions, enabling employment as part of a near-real time observation system or to formulate decisions for the protection of the seawater environment. Amos, C. L., Daborn, G. R., and Christian, H. A.: In situ erosion measurements on fine-grained sediments from the Bay of Fundy, Mar. Geology, 108, 175–196, 1992. Amos, C. L., Feeney, T., Sutherland, T. F., and Luternauer, J. L.: The stability of fine-grained sediments from the Fraser River Delta, Estuar. Coast. Shelf Sci., 45, 507–524, 1997. Anagnostou, Ch., Kaberi, E., Karageorgis, A., Kontoyiannis, H., Krassakopoulou, E., Pagou, K., Pavlidou, A., and Stavrakakis, S.: Matter transfer in a land-basin shelf: NW Aegean area – Mediterranean Sea, Proceedings of the International Workshop on Environmental Biochemistry, New Delhi, 347–368, 1998. Barros A. P. and Baptista, A. M.: An Eulerian-Lagrangian Model for Sediment Transport in Estuaries, in: Estuarine and Coastal Modeling, edited by: Spaulding, M., ASCE, 102–112, 1990. Black, K. S.: Microbiological factors contributing to erosion resistance in natural cohesive sediments, in: Cohesive Sediments, edited by: Burt, N., Parker, R., and Watts, J., John Wiley & Sons Ltd, Chichester, 231–244, 1997. Burd, A. and Jackson, G. A.: Prediction particle coagulation and sedimentation rates for a pulsed input, J. Geophys. Res., 102(C5), 10 545–10 610, 1997. Estournel, Cl.: Modelling the transport of particulate matter on the Gulf of Lion continental shelf, METRO-MED, Final Scientific Report, Vol. I, 2000. Ganaoui, O. El, Schaaff, E., Boyer, P., Amielh, M., Anselmet, F., and Grenz, C.: The deposition and erosion of cohesive sediments determined by a multi-class model, Estuar. Coast. Shelf Sci., 60, 457–475, 2004. Ganoulis, G. G.: Engineering risk analysis of water pollution, VCH Pubs, Weinheim, 1994. Houwing, E.-J.: Determination of the Critical Erosion Threshold of Cohesive Sediments on Intertidal Mudflats along the Dutch Wadden Sea Coast, Estuar. Coast. Shelf Sci., 49, 545–555, 1999. Karageorgis, A., Anagnostou, Ch., Georgopoulos, D., and Albouisson M.: Distribution of suspended particulate matter determined by in-situ observations and satellite images in the NW Aegean Sea (Greece), Geo-Marine Letters, 20, 93–100, 2000. Karageorgis, A. P. and Anagnostou, Ch. L.: Particulate matter spatial-temporal distribution and associated surface sediment properties: Thermaikos Gulf and Sporades Basin, NW Aegean Sea, Cont. Shelf Res., 21, 2141–2153, 2001. Karamanos, H. and Polyzonis, E.: Dynamics of matter transfer and biogeochemical cycles: their modelling in coastal systems of the Mediterranean Sea, METRO-MED, Second Annual Scientific Report, Vol. II, 1998. Karamanos, H., Durrieu de Madron, X., Polyzonis, V., and Ludwig, W.: The adjacent area as fresh water and particulate matter contributor to the coastal zone of the Mediterranean Sea: Gulf of Lyons and Thermaikos Gulf, METRO-MED, Final Scientific Report, Vol. I, 2000. Kontoyiannis, H. and Papadopoulos, V.: Hydrography and circulation of the Thermaikos plateau in February 1998, July 1997 and May 1997 and a simple comparison of geostrophic vs ADCP-measured flow fields in approaching the estimation of horizontal mass fluxes, METRO-MED, Second Annual Scientific Report, Vol. I, 1998. Korres, G. and Lascaratos, A.: A one-way nested eddy resolving model of the Aegean and Levantine basins: implementation and climatological runs, Ann. Geophys., 22, 205–220, 2003. Kourafalou, V. H., Barbopoulos, K. A., Tsiaras, K., and Staneva, J. V.: Numerical studies on shelf dynamics: North Aegean Sea and Northwestern Black Sea, International Conference on Oceanography of the Eastern Mediterranean and Black Sea, Ankara, Turkey, 2002. Kourafalou, V. H. and Barbopoulos, K.: High resolution simulations on the North Aegean Sea seasonal circulation, Ann. Geophys., 22, 251–265, 2003. Kourafalou, V. H., Savvidis, Y. G., Krestenitis, Y. N., and Koutitas, Ch. G.: Modelling studies on the processes that influence matter transfer on the Gulf of Thermaikos (NW Aegean Sea), Cont. Shelf Res., 24, 203–222, 2004. Kourafalou, V. H. and Tsiaras, K. P.: A nested circulation model for the North Aegean Sea, Ocean Sci., 3, 1–16, 2007. Krestenitis, Y. N.: Mathematical Study of the three-dimensional coastal circulation by algebraic transformations, PhD thesis, AUTh, Thessaloniki, in Greek, 1987. Krishnappan, B. G. and Marsalek, J.: Transport characteristics of fine sediments from an on-stream stormwater management pond, Urban Water, 4, 3–11, 2002. Lykousis, V., Collins, M. B., and Ferentinos, G.: Modern sedimentation in the N.N. Aegean Sea, Mar. Geology, 43, 111–130, 1981. Maa, J. P. Y., Wright, L. D., Lee, C. H., and Shannon, T. W.: VIMS Sea Carousel: A field instrument for studying sediment transport, Mar. Geology, 115, 271–287, 1993. Maa, J. P., Sanford, L., and Halka, J. P.: Sediment resuspension characteristics in Baltimore Harbor, Maryland, Mar. Geology, 146, 137–145, 1998. Mellor, G. L.: Introduction to Physical Oceanography, Princeton University, New Jersey, 1996. Metha, A. J.: Hydraulic Behaviour of fine sediment, Coastal, Estuarial and harbour engineer's reference book, Abott & Price, Chapman & Hall (Pubs.), London, 577–585, 1993. McLane, M.: Sedimentology, Oxford University Press, New York, 1995. Mitchener, H. and Torfs, H.: Erosion of mud/sand mixtures, Coastal Engineering, 29, 1–25, 1996. Moustaka, M.: Oceanography, a biological approach, Exin Pubs., Thessaloniki, in Greek, 1997. O' Brien, J. J. (Ed.): Advanced Physical Oceanographic Numerical Modelling, NATO ASI Series, 1986. Olson, D., Kourafalou, V., Johns, W., Samuels, G., and Veneziani, M.: Aegean Surface Circulation from a Satellite-tracked Drifter Array, J. Phys. Oceanography, in press, 2007. Papadopoulos, A., Katsafados, P., Kallos, G., and Nickovic, S.: The Weather Forecasting System for Poseidon – an overview, The Global Atmosphere and Ocean System, 8(2–3), 219–237, 2002. Pohlmann, T. and Puls, W.: Currents and Transport in water, in: Circulation and Contaminant Fluxes in the North Sea, Springer-Verlag Science, Michigan, 555–605, 1994. Poulos, S. E,, Chronis, G. Th., Collins, M. B., and Lykousis, V.: Thermaikos Gulf Coastal System, NW Aegean Sea: an overview of water/sediment fluxes in relation to air-land-ocean interactions and human activities, J. Marine Syst., 25, 47–76, 2000. Rodean, H. C.: Stochastic lagrangian models of turbulent diffusion, Meteorological Monographs, American Meteorological Society, Massachusetts, 1996. Rodi, W.: Turbulence models and their application in Hydraulics, IAHR, 1993. Savvidis, Y., Koutitas, C., and Krestenitis, Y.: Development and application of a three dimensional cohesive sediment transport mathematical model, Journal of Marine Environmental Engineering, 6, 229–255, 2001. Schünemann, M. and Kühl, H.: Experimental investigations of the erosional behaviour of naturally formed mud from the Elbe Estuary and adjacent Wadden Sea, Germany, in: Nearshore and Estuarine Cohesive Sediment Transport, edited by: Mehta, A. J., Coastal and Estuarine Studies, 42, 314–330, 1993. Schweim, C., Bouchard, J. P., Welzel, J., Spork, V., and Köngeter, J.: Sediment management during reservoir depletion – experimental investigations of mud siltation and resuspension, 7th International Symposium on River Sedimentation, Hong Kong, 1998. Soukissian, T. H., Chronis, G. T, Nittis, K., and Diamanti, Ch.: Advancement of Operational Oceanography in Greece: The Case of the Poseidon System, The Global Atmosphere and Ocean System, 8, 119–133, 2002. Tolhurst, T. J., Riethmüller, R., and Paterson, D. M.: In situ versus laboratory analysis of sediment stability from intertidal mudflats, Cont. Shelf Res., 20, 1317–1334, 2000. Toorman, E. A., Bruens, A. W., Kranenburg, C., and Winterwerp, J. C.: Interaction of Suspended Cohesive Sediment and Turbulence, Proc. INTERCOH, 2000. Wang, X. H. and Pinardi, N.: Modeling the dynamics of sediment transport and resuspension in the northern Adriatic Sea, J. Geophys. Res., 107(C12), 18-1–18-23, 2002. Watts, C. W., Tolhurst, T. J., Black, K. S., and Whitmore, A. P.: In situ measurements of erosion shear stress and geotechnical shear strength of the intertidal sediments of the experimental managed realignment scheme at Tollesbury, Essex, UK, Estuar. Coast. Shelf Sci., 58, 611–620, 2003. Widdows, J., Brinsley, M. D., Bowley, N., and Barrett, C.: A Benthic Annular Flume for In Situ Measurement of Suspension Feeding/Biodeposition Rates and Erosion Potential of Intertidal Cohesive Sediments, Estuar. Coast. Shelf Sci., 46, 27–38, 1998. Winterwerp, J. C.: A simple model for turbulence induced flocculation of cohesive sediment, J. Environ. Eng., 36(3), 309–326, 1998. Winterwerp, J. C.: On the dynamics of high-concentrated mud suspensions, Judels Brinkman & Ammerlaan, Delft, 1999.