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Prediction of Cohesive Sediment Transport and Bed Morphodynamics in Estuaries and Coastal Zones with Integrated Numerical Simulation Models

Deliverables

Within the context of establishing well validated physical and mathematical descriptions of the behavior and fate of concentrated near-bed suspensions and their interaction with the water column and the sediment bed a large amount of data was generated. One of the project deliverables is an internet oriented data base containing the data of field surveys and laboratory experiments e.g. information about sediment properties, hydrodynamics, geometry, bathymetry, concentrations, instrumentation, data-processing etc. Also the results of numerical simulations for a number of test cases are stored in the data base for use as a benchmark or inter-comparison with other models. The data base is accessible at: http://www.hydromech.uni-hannover.de/cosinus/database or via the COSINUS web site at: http://sun-hydr-01.bwk.kuleuven.ac.be/COSINUS/cosinus.html The database contains: 1. Data from field measurements: the (COSINUS) Tamar Estuary Experiment (sediment properties, floc properties, bed properties) September 1998 and the SILTMAN experiment (1996). 2. Data from laboratory measurements Consolidation and strength evolution of mud Annular flume experiments on the entrainment by a turbulent CBS. Consolidation columns tests Grid tank experiments. 3. Data from numerical simulations1 DV case Siltman case. Case studies: Weser, Loire, Tamar estuary. The description of the data (meta-data) and the data itself are organised in packages which are comparable to reports on paper with a data-disc attached. One package contains the description and the data of one set of experiments and was supplied by only one participant of the COSINUS project. The data base is a "distributed" data base. It means that although all data are accessible through the COSINUS web page, the data are "physically" on the server of the institute that produced the data. In this way the producer of the data can quality check the data and maintain the data base up to date. All data are available in a standard ASCII format. Only meta-data (descriptions) are stored centrally in the data management system in Hanover. The actual data (numbers) are stored locally at the institute or organization, which generated the data (distributed data storage).The data-management system is Internet based. The user gets access to the system with a Java-enabled browser via Internet. No special software installation on the computer of the user is required. The actuality of the information is always assured. The meta-data (physically located in Hanover) and the data are connected by a link. Data are supplied by putting a copy of the data (plain numbers in ASCII-format) at a place where the internet-server of the supplying institute has access to them. As such, the data supplier has full responsibility for its data. The database input tool is used to input/change the meta-data (description). With this tool the data can be edited and organized and links connecting the data can be generated. Write access to meta-data is only given to the user who supplied it. When accessing data via the database, the user first sees the meta-data before getting the opportunity to download the data itself. Inside the database, meta-data are organized in packages. Starting with an introduction, the description may branch down into several sub-chapters. Each (sub-) chapter again may have (sub-) sub-chapters and so on. This opens up the opportunity to construct a branched description, which helps give explanations relevant for a group of data of a higher level and to supply special information for individual data sets on a lower level. A package is comparable to a report on paper describing a group of measurements, which were obtained during laboratory experiments or field surveys, in a text, which refers to tables or figures in the appendix. A tradition of good scientific practice on data documentation is not interrupted through the application of a WWW-based data-management. If needed (library, archiving, etc.), the database packages can be transformed into reports without much additional effort, i.e. "downward compatibility". The external part of the database has been linked to the COSINUS homepage and contains packages that are ready and checked. The development and editing of a package is done in the internal part. The description of the data (meta-data) and the data itself are organised in packages which are comparable to reports on paper with a data-disc attached. One package contains the description and the data of one set of experiments and was supplied by only one participant of the COSINUS project. All data are available in a standard ASCII format. http://www.hydromech.uni-hannover.de/cosinus/database or via the COSINUS web site: http://sun-hydr-01.bwk.kuleuven.ac.be/COSINUS/cosinus.html The database contains: 1. Data from field measurements: the (COSINUS) Tamar Estuary Experiment: sediment properties, floc properties, bed properties (SedErode), (HR Wallingford, University of Plymouth, University of Wales at Bangor, University of Oxford) the SILTMAN experiment (Delft Hydraulics, 1996). 2. Data from laboratory measurements. Consolidation and strength evolution of mud (TUDelft, UOX) Annular flume experiments on the entrainment by a turbulent CBS (TUDelft) Consolidation column data processing (KULeuven) Grid tank experiments (LEGI). 3. Data from numerical simulations: 1 DV case (LNHE). Case study Weser (UHA) Schematic Esturary (LNHE) Case study Loire (LNHE) Case study Tamar estuary (DHI)
The management of coastal zones and estuaries requires accurate and detailed knowledge to cope with their problems such as wetland protection and restoration, maintenance of navigation channels, dredging and dredged material relocation, effects of construction works on siltation and turbidity levels, pollutant transport, etc. Development and application of this knowledge requires detailed mathematical models, amongst which full three-dimensional codes. The physical understanding and mathematical description or �modelling� of the processes however was inadequate, especially with respect to the presence of concentrated benthic (near-bed) suspension layers (CBS). The objective of COSINUS was to establish well validated physical and mathematical descriptions of the behaviour and fate of concentrated near-bed suspensions (CBS or �fluid mud�) and their interaction with the water and the sediment bed. Different processes have been studied in detail: turbulence damping in sediment laden flow; turbulence production due to internal waves in concentrated suspensions; flocculation; generation, properties and entrainment of CBS; bed strength development and erosion of mud beds. Since there seemed to be a lack of experimental data on the role of flocculation and turbulence in the formation and erosion of mud beds and on the formation of CBS, an experimental programme was set up to obtain these data. The detailed process models have been parameterised to obtain relatively simple formulations which can be implemented into currently used 3D and 2DH engineering system models. The performance of the improved system models has been tested by application of the models to a schematic estuary for which 2DV solutions with the detailed research models were used as a reference. It is felt that great progress has been made in the physically based description of cohesive sediment dynamics with respect to the formulation of turbulence damping functions; the modelling of the rheology of a CBS, incl. consolidation; the modelling of flocculation and the modelling of erosion and entrainment of CBS. Engineering software tools have been improved to enable better predictions of mud dynamics for the benefit of estuarine and coastal managers. The managing authorities of coastal waters and estuaries face a large number of problems related to cohesive sediment transport, sedimentation and erosion, such as: -How to maintain safe navigable depths (at minimum cost)? -Where and how to dump dredged material? -How can the volume of wetlands be maintained or increased? -What will happen to the location of the turbidity maximum after constructing new harbour basins or deepening the navigation channels? Etcetera.. To answer these questions, one needs a model capable of simulating the many different and interrelated (cohesive) sediment processes occurring in coastal and estuarine waters, which can predict natural phenomena and the effects of human interference. Unfortunately, the presently used models were unable to simulate accurately the many different and interrelated cohesive sediment processes occurring in coastal and estuarine waters due to too many simplifications. Therefore there was a need for an integrated sediment transport management model in which all relevant physical processes are integrated. Progress in the understanding and the mathematical description of the different processes and the increasing capacity and speed of modern computers opens new doors toward the operational use of much more detailed models. Therefore, the goal of the COSINUS project was to contribute to the development of an integrated sediment transport management model. "Integrated" refers to the integration of all relevant physical processes over the entire water column and the sediment bed and their interactions. The major exploitable results of this project are: -Well validated process modules and their parameterisations. -A framework for integrated numerical simulations. -Guidelines for model calibration and a database for model validation. Exploitation of the results is achieved through their implementation in commercially available engineering models (software codes), currently used in advisory studies for managerial authorities by DHI, LNHE, Delft Hydraulics and H.R. Wallingford and their clients: the engineering models are sold to and used by a great number of consulting engineering bureaus and local and governmental authorities. The parameterisations and their implementation can also be used by research institutes within a more general study of estuarine and coastal system dynamics e.g. for studies related to pollutants exchange between the sediment bed and the water column, studies of morphological stability or morphological changes of mud flats etc. The different process modules and their parameterisations deal with are: -The modelling of turbulence damping (buoyancy effect) and turbulence generation (internal wave turbulence production) in concentrated suspensions. -The development of a floc model which allows the calculation of the settling velocity of flocs in relation to turbulence, concentration, residence time and, if possible, organic content. -The modelling of the exchange of mass and momentum at the fluid mud/water interface. -The identification and quantification of relevant processes for generating and maintaining benthic suspensions (CBS). -The modelling of the development of erosion resistance (strength) in mud beds.

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