Morphological predictor for mixed beds

How to Use

The intended users of the sand-mud-bed module are scientists and professionals with affinity to sediment transport. The bed module can be used in a simple 1-D mode with a small number of sediment fractions and bed layers. It can also be used in a more advanced 3-D model with many fractions and layers. The best choice depends on the questions to be answered, the complexity of the system, the quality of available field data and the modeller’s experience.

Requirements

The bed module is open-source and has been developed by Deltares. It can be applied in three different ways:

1. The sand-mud module is available as part of the Delft3D open source software environment (see repository; registration – free of charge – required). In this way it can be used together with all other features within this environment, for instance in comprehensive 3-D model studies in the detailed design phase of a project; to be able to use the module in this setting, the Delft3D software environment should be installed at the user’s computer system;
2. For a quick assessment of potential bed level and bed composition changes due to human or natural changes to the environment, it can be run in 1-D mode as a stand-alone Matlab library;
3. The plain Fortran code code of the module is available as well; this requires Fortran programming skills and a Fortran compiler and enables incorporation of the sand-mud bed module in any (open source) software environment.

Phased plan process

1. The first step in applying the bed module is to define the prevailing hydrodynamic forcing (currents + waves). The forcing can be computed with a hydrodynamic and wave model such as Delft3D and SWAN, or can be supplied by the user based on analytical expressions (in 1-D mode).
2. The second step is to define sediment boundary conditions (supply) and sediment properties such as settling velocity and erosion properties for multiple fractions. Generally some calibration is required to reproduce the observed spatial and vertical distribution of bed composition. In 1-D mode, the boundary condition is the sediment concentration in the water column.
3. The third step is to adapt the hydrodynamic forcing to the future situation (either computed by a hydrodynamic model or defined by the user) and to define changes in sediment supply if necessary.
4. The fourth and last step is to compute changes in bed level and bed composition in the new situation, with the corresponding changes in hydrodynamic forcing or sediment supply.

Advice

To apply the bed module successfully, some local information on hydrodynamic forcing, sediment composition and sediment properties is required. Although the tool is simple to use, especially in its 1-D mode, we recommend users to acquire a basic understanding of the implemented formulations prior to practical application. This is important for the interpretations of the results. Start simple and gradually extend the model’s complexity (number of sediment fractions and layers) as far as necessary. Be aware of the time scale of bed composition and/or bed level changes compared with the simulation time scale.