Monitoring the convergence status of a model is important but often difficult due the complexity of the sediment transport models. The sediment log output may be grouped similar to the HDF5 spatial output as:

Sediment Transport (sediment concentrations)
Sediment Bed (grain class fractions and dry densities in the active layer)

In addition, the logging output is written out to two different places: (1) the Computation Log File (.bco), and (2) the HDF5 Output File (.p.hdf).
The amount of information which is written to the Computation Log File depends on the sediment Output Level (see Section 2.4 Sediment Output Options) and the convergence status. The log output in the Computation Log File is output only when a convergence tolerance is exceeded for Output Levels less than 5. If the output level is 5 or 6, a log record is written at a constant computation time step interval. For an Output Level of 5, the log record only contains convergence information for the last outer-loop iteration. For an Output Level of 6 the log record contains convergence information for all iterations.

HDF5 Log Output

The log output in the HDF5 Output File is written to the same location as the Sediment Transport and the Sediment Bed output blocks and is therefore written at the corresponding output intervals. The output interval for the Sediment Transport and the Sediment Bed output blocks can be controlled by the user by specifying a multiple of the Mapping Output Interval (see Section 2.4 Sediment Output Options for details). The log output is written as floating point datasets instead of compound datasets or other forms for computational speeds.

Sediment Transport

The log output for Sediment Transport is written in the HDF5 Output File under

Dataset Name: Log Sediment Transport
Dataset Path: /Results/Unsteady/Output/Output Blocks/Sediment Transport/Unsteady Time Series/2D Flows Areas/<2D Flow Area Name>/

where <2D Flow Area Name> is the name of each 2D flow area.

Table 1. Sediment Transport Log Output. Note: HDF5 columns begin at 0.

Column	Log Output Variable	Units
0	Overall convergence status flag	-
1	Transport convergence status flag	-
2	Number of outer-loop iterations	-
3	Maximum total total-load concentration	mg/L
4	Cell location of maximum total total-load concentration	-
5	Maximum fractional total-load concentration	mg/L
6	Cell location of maximum fractional total-load concentration	-
7	Grain class corresponding to maximum fractional total-load concentration	-
8	Concentration maximum absolute correction for all grain classes	mg/L
9	Cell location of maximum absolute concentration correction for all grain classes	-
10	Grain class corresponding to maximum absolute concentration correction for all grain classes	-
11	Percent of active grid	%
12	Minimum total inner loop iterations (only for iterative matrix solvers)	-
13	Grain class corresponding to minimum inner loop iterations (only for iterative matrix solvers)	-
14	Maximum total inner loop iterations (only for iterative matrix solvers)	-
15	Grain class corresponding to maximum inner loop iterations (only for iterative matrix solvers)	-
16	Maximum root-mean-squared residual of inner-loop iterations (only for iterative matrix solvers)	-
17	Grain class corresponding to maximum root-mean-squared residual of inner-loop iterations (only for iterative matrix solvers)	-

Currently when the model diverges, it stops the simulation. In future versions, diverged time steps will be repeated with subcycles in order to try to obtain a converged solution. Usually divergence indicates a NaN (not a number for bed change, bed fractions, or sediment concentrations). However, it could also mean an internal divergence tolerance was exceeded. Future versions of the model will include more information on how the model diverged. A description of the convergence flags are described in the table below.

The convergence status flags indicate different model states (see Table 1). A status is computed each outer iteration for the sediment transport and bed calculations. The overall convergence status takes into account transport and bed sorting.

Table 2. Convergence Status Flags.

Status Flag	Status Name	Description
-1	Diverged	The solution has diverged. Divergence is determined with a variety of tolerances and checks for many variables.
1	Iterating	Either the convergence tolerances or minimum number of iterations have not been satisfied.
0	Converged	Both the convergence tolerances and minimum number of iterations have been satisfied.
2	Continue	Either the convergence has stalled, or the maximum number of iterations has been reached. The solution will continue to the next time step.

Sediment Bed

The logging output for the Sediment Bed is written in the HDF5 Output File under

Dataset Name: Log Sediment Bed
Dataset Path: /Results/Unsteady/Output/Output Blocks/Sediment Bed/Unsteady Time Series/2D Flows Areas/<2D Flow Area Name>/

where again <2D Flow Area Name> is the name of each 2D flow area.

Table 3. Sediment Bed Log Output. Note: HDF5 begin start at 0.

Column	Log Output Variable	Units
0	Overall status flag	-
1	Sediment bed status flag	-
2	Number of outer-loop iterations	-
3	Maximum absolute value of active layer fraction correction (difference between outer-loop iteration values)	%
4	Cell location of maximum absolute value of active layer fraction correction	-
5	Subarea corresponding to maximum absolute value of active layer fraction correction	-
6	Grain class corresponding to maximum absolute value of active layer fraction correction	-
7	Number of avalanching iterations	-
8	Number of avalanches at last iteration	-
9	Maximum bed change due to avalanching	ft or m
10	Cell location of maximum bed change to due avalanching	-