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Context and purpose
Shoal nourishments can be applied in areas where structural erosion of shoals leads to loss in intertidal area and important ecological habitats. The Nourishment Tool was developed to aid in the planning and design of such nourishments. The Nourishment tool is one of the tools implemented in Delft Dashboard. The main purpose of the tool is to quickly evaluate the effect of a shoal nourishment on the area of interest. The computations are fast, allowing to simulate 10 years in a matter of minutes. This makes the tool very useful in comparing different nourishment strategies or designs, particularly in the initial or tender stages of a project.
The nourishment tool makes use of a bathymetrical map and a residual flow pattern of the area of interest. Through Delft Dashboard, the tool is linked to all kinds of open databases for bathymetry, and users are also enabled to add their own classified datasets to the tool. Maps with residual flow patterns can be obtained from hydrodynamic model computations, for instance with Delft3D, or from other sources of data. It is also possible to schematically account for biogeomorphological effects like bioturbation or biostabilisation, by adjusting the equilibrium concentration.
Output for the defined period is presented in 4 graphs, showing (clockwise):
- the sedimentation and erosion patterns of the nourished sediment;
- the thickness of the nourishment layer;
- the changes in bed level, and
- the equilibrium concentration.
The General User Interface (GUI) of Delft Dashboard is intended to be rather intuitive to enable a wide range of users to use the software. Nevertheless, some affinity with coastal modelling (especially with Delft3D) may come in handy for using Delft Dashboard and its tools to its full extent. In the interface of the Nourishment Tool, the desired nourishment can easily be drawn on a bathymetrical map of the area of interest.
Please note that the quality of the results largely depend on the quality of the bathymetrical map and the residual flow field that is used.
The Nourishment tool can potentially be used for any type of environment where the hydrodynamics are tide-dominated, like estuaries and tidal basins. These environments often play an important role in the ecosystem of the area, where conservation of the intertidal shoals and flats is paramount for the functioning of the ecosystem.
The quick nature of the tool makes it particularly useful for the initial project phases, i.e. initiation and planning & design. Generally, more dedicated and detailed modelling is required for the construction and operation & maintenance phases.
The Nourishment tool is implemented in Delft Dashboard, which is available (free of charge) both as a standalone executable and as Matlab code. The executable can run without having Matlab installed on the user's computer. However, this option requires installation of the Matlab Compiler Runtime (MCR). The installation notes for installing the Delft Dashboard executable can be found in the OpenEarth Product Suite. Matlab users can also download the Matlab code which is available in the OpenEarthTools repository(user password required). For downloading the Matlab code it is strongly recommended to use the subversion repository system. More information on this, plus user registration, can be found on the OpenEarth website.
General User interface (GUI)
The figure below shows the GUI of the Nourishment tool:
The Top menu describes the most generic functions of Deft Dashboard, which allows for switching between different models, toolboxes, bathymetries, coordinate systems and loading & saving of working directories and files generated during your Delft Dashboard session. You can access the Nourishment tool by opening the toolbox menu. The Map View window visualizes the map with the bathymetry, residual flow field and nourishment polygons. In default mode, Delft Dashboard starts up with the GEBCO 2008 world bathymetry in the background.
The working space of the Nourishment tool has four tabs. The main setup of the nourishment scenario is done in the first tab. The outline of the nourishment can simply be drawn on the map by a polygon, or a polygon can be loaded from file. The nourished volume can be defined for each separate polygon, by determining the total volume or a uniform layer thickness. A detailed residual current field can be loaded from a Matlab file, but it is also possible to use a uniform field.
For more detailed documentation, reference is made to the documentation (draft version) of Delft Dashboard. To get started using Delft Dashboard please have a look at the webinar in which the general functionality as well as some specific toolboxes are explained. On the open source website of Deltares there is a Delft Dashboard user forum. Here users can post questions and report bugs.