Mud transport model for the Scheldt estuary in the framework of LTV Thijs van Kessel, Joris Vanlede, Marieke Eleveld, Daphne van der Wal © Deltares, 2008 Prepared for: Waterdienst Mud transport model for the Scheldt estuary in the framework of LTV Thijs van Kessel, Joris Vanlede, Marieke Eleveld, Daphne van der Wal Report December 2008 Z4594 Client Waterdienst Title Mud transport model for the Scheldt estuary Abstract Vanaf 2006 wordt gewerkt aan de ontwikkeling van een slibtransportmodel van het Schelde-estuarium in het kader van LTV (Lange Termijn Visie), luik Toegankelijkheid. Het doel van dit model is om de beheerders van het Schelde-estuarium te ondersteunen. De kernvraag van dit project is tweeërlei. Enerzijds is er behoefte aan kennis van de huidige slibdynamiek en -balans en de bepaling van de autonome ontwikkeling hiervan. Anderzijds speelt de vraag naar het effect van diverse ingrepen op de slibdynamiek en –balans in verhouding tot de autonome ontwikkeling. Nadat in 2006 en 2007 een literatuurstudie is uitgevoerd en het slibmodel is opgezet, gekalibreerd en toegepast voor een eerste beheersvraag (havenstorting Sloehaven), is hierop in 2008 voortgebouwd door middel van de volgende activiteiten: jaarsimulaties, analyse seizoensdynamiek, validatie aan de hand van langdurige meetreeksen, ondermeer bij Antwerpen. Verder is ook het effect van de tweede verruiming als beheersvraag opgenomen. In 2008 werd er tevens vanuit remote sensing gegevens informatie afgeleid over het zwevend stof gehalte (SPM) in de bovenste laag van de waterkolom, en over het slibgehalte in de bovenste laag van de bodem op platen. Deze gegevens bieden door hun synoptisch karakter een waardevolle extra calibratie- en validatieset voor het slibmodel. Uit de modelvalidatie blijkt dat de slibdynamiek redelijk goed door het model wordt gereproduceerd, maar dat de sterkte van de seizoensdynamiek en van de estuariene circulatie nog onvoldoende door het model worden gereproduceerd. Deze aandachtspunten worden opgenomen in het vervolgtraject van dit project. De voorbeeldtoepassing van het slibmodel voor 2008, namelijk het effect van de tweede verruiming, is berekend door in het model de drempels op de situatie voor 1997 te brengen. Resultaten op basis van deze nieuwe bathymetrie wijzen erop dat de tweede verruiming slechts een klein effect heeft gehad op de slibconcentratie (minder dan 2%). Deze invloed is zeer beperkt in vergelijking tot de natuurlijke variatie in slibconcentratie door getij, wind en seizoenseffecten. References Raamovereenkomst 31007973, SPA27,1A: LTV Toegankelijkheid Ver Author Date Remarks Review Approved by Thijs van Kessel 23/12/2008 C. Kuijper Schilperoort Joris VanledeVanlede, Marieke Eleveld Daphne van der Wal Project number Z4594 mud transport, three-dimensional models, estuary models, Scheldt, remote Keywords sensing Number of pages 94 Classification None Status Final Mud transport model for the Scheldt Z4594 December 2008 estuary Contents 1 Introduction .........................................................................................................1 2 Remote sensing data ..........................................................................................2 2.1 Upper part of the water column ................................................................2 2.1.1 Introduction...................................................................................2 2.1.2 Method..........................................................................................2 2.1.3 Results: Validated MERIS-FR SPM products..............................9 2.1.4 Pilot SPM from Landsat .............................................................11 2.2 Bed roughness and bed composition .....................................................15 2.2.1 Introduction.................................................................................15 2.2.2 Bed roughness from SAR ..........................................................15 2.2.3 Mud content of the sediment from SAR.....................................18 2.2.4 Mud content from optical remote sensing..................................22 3 Model calibration and validation .....................................................................23 3.1 Hydrodynamics .......................................................................................23 3.1.1 Numerical grid and resolution ....................................................23 3.1.2 Model characteristics .................................................................23 3.1.3 Calibration of model east of Cadzand-Westkapelle (simF10) .....................................................................................24 3.1.4 Validation of model with ZUNO boundary (simG06)..................25 3.1.5 Discussion..................................................................................27 3.2 Mud transport..........................................................................................28 3.2.1 Year simulations.........................................................................28 3.2.2 Validation on remote sensing.....................................................29 3.2.3 Mud balance...............................................................................31 3.2.4 Validation on measurements near Antwerp...............................33 4 Model application..............................................................................................38 4.1 2nd fairway enlargement..........................................................................38 4.2 Dredged material release at Zeebrugge.................................................39 5 Conclusions and recommendations...............................................................40 5.1 On data ...................................................................................................40 5.2 On model development...........................................................................41 5.3 On model application..............................................................................42 5.4 Synthesis and outlook to LTV- Nature and MONEOS ...........................42 Deltares, Flanders Hydraulics, IVM, NIOO i Mud transport model for the Scheldt Z4594 December 2008 estuary 6 References .........................................................................................................43 Appendices A Details on remote sensing data acquisition...................................................47 A.1 SIOPs: the optical absorbing and scattering properties of substances in Western Scheldt and North Sea waters..........................47 A.2 Selected suspended particulate matter (SPM) products derived from MERIS remote sensing images for 2006 .......................................50 A.2.1 Western Scheldt sIOP parameterisation (Restwes99Oroma02mean).......................................................50 A.2.2 North Sea sIOP parameterisation (Belgica2000).......................54 A.3 Vertical tidal stage (in m NAP) at image date and time..........................60 B Details on remote-sensing mudflats...............................................................61 B.1 Maps of bed roughness RMSz: 2006 .....................................................61 B.2 Maps of the mud content of the sediment: 2006 ....................................63 C Details on hydrodynamic model......................................................................65 D Details on mud model.......................................................................................76 D.1 Time series .............................................................................................76 D.2 Comparison with OBS data ....................................................................80 D.3 Seasonal dynamics.................................................................................81 D.4 Comparison between 3-month period, 2000 and 2006..........................85 D.5 Comparison between mud model and remote sensing data..................86 D.6 Thalweg plots..........................................................................................92 Deltares, Flanders Hydraulics, IVM, NIOO ii Mud transport model for the Scheldt Z4594 December 2008 estuary 1 Introduction In 2006, a work plan was conceived for the development of a mud transport model for the Scheldt estuary in the framework of LTV (Long Term Vision) (Winterwerp and De Kok, 2006). The purpose of this model is to support managers of the Scheldt estuary with the tools to evaluate a number of managerial issues. Five phases have been defined in the work plan: 1 set-up of mud model 2 elaboration of managerial questions 3 year simulations 4 detail studies 5 sediment mixtures. In 2006, the first two phases were initiated. The set-up of the hydrodynamic and mud transport model was reported in Van Kessel et al. (2006), whereas the managerial issues were elaborated in Bruens et al. (2006). In 2007, the activities were based on the original work plan (items 1 through 3), but also took into account the findings from the set-up of the mud model and the discussions with Scheldt estuary managers during 2006. In short, most activities for 2007 fell into the following two categories, which are reported in more detail in Van Kessel et al. (2007): 1 further improvement of the mud transport model; 2 providing support for managerial issues: dredging and dumping strategy at Sloe harbour. In 2008, phases 3 and 4 were initiated, i.e. year simulations with the hydrodynamic and mud model and the first development