Several user capabilities are available in the Options menu. These options provide analysis flexibility in several aspects of the computations.
User Defined Particle Sizes
The grain size bins used by default in HEC-RAS are based on a standard log base 2 scale based on the American Geophysical Union (AGU). This option allows the user to redefine the particle size class ranges to either simplify the analysis or provide more detail in a certain grain size range. The user can enter in the upper and lower bound of the first grade class and the upper bound of the rest of the grade classes in the figure below. Lower bounds automatically adjust to eliminate gaps. The grain class labels can also be edited. Edited grain class names and sizes will appear in the corresponding dialogs. If the Defaults button is selected, all of the grid entries will return the AGU default values.
Multiple Transport Functions
The multiple transport functions option allows the user to specify distinct transport functions for different grain classes. A more detailed description of this feature is included on page 5.
Remove Cross Section from Sediment Reach
It may occasionally be desirable to omit one or more cross sections within a defined sediment reach from the hydraulic parameters averaging and sediment transport computation. If the hydrodynamics at a cross section are spurious and non-typical they may be omitted by de-selecting them in the editor depicted in the figure below.
Set Budget Tolerances
When SIAM displays output, results are color coded in three categories: sediment deficit, surplus or equilibrium. Since the supply will never precisely equal the capacity, equilibrium is a range of acceptable deficit or surplus. This acceptable zone is strongly site and project specific and therefore must be entered by the user. The budget tolerance editor (below) allows the user to set a range of acceptable fluctuation (in tons/year) that will be displayed as equilibrium for each reach.
