HEC-EFM offers an option to cycle computations, replacing one piece of flow regime input in each iteration. This option is useful when designing hydrographs or designing topography – that is, considering many hydrograph options with a single topography (reservoir reoperations) or considering many topographic options for a single flow hydrograph (earthwork).
Cyclic application of HEC-EFM is initiated through the “File – Flow Regimes – Batch Recalculate…” menu option (Figure 67). Users specify which flow regime part to cycle through, input data files and records, and output location and naming conventions. A master switch for exporting results to DSS is provided here because this feature has the potential to generate much output. The switch is a checkbox option labeled Compute arrays (export to DSS).
Figure 67. The “Batch Recalculate…” option in HEC-EFM allows users to cycle computations by replacing data associated with active flow regimes.
All other output controls (e.g., output settings and write computation arrays) remain in effect. Several options are provided for flow regime output names as combinations of pathname parts and user-defined prefixes and suffixes.
Again, it is important to note that only one data part of the flow regime is changed with each iteration. An early application of this feature involved testing several hydrographs to determine which generated the most ecological benefits. Flow regimes comprised of a flow time series and a local rating curve were added for locations along the river and made active. HEC-EFM was then used to test the set of hydrographs, each hydrograph being tested independently for all active flow regimes (locations). Output were written to tables and to HEC-DSS for subsequent analyses. Figure 67 shows a scenario in which 50 hydrographs (C = FLOW) will be tested.