In GeoHECRAS, the Restart Options panel of the Unsteady Flow Computational Options dialog box allows the user to write out the initial conditions file(s) for an entire simulation, sometimes called a Hot Start file. A Hot Start file can be used to set the system’s initial conditions for a subsequent run. It is commonly used in real-time forecasting, where the user wants to use the results at a specific time from a previous run to be the initial conditions of the next run.

The following section describes how to interact with the Restart Options panel of the Unsteady Flow Computational Options dialog box.
Write Initial Conditions Restart Files During Simulation
The user can check this section to enable the content and define the simulation period for writing the initial conditions file.
The following options are provided in this panel:
- Hours from simulation beginning
Selecting this option allows the user to define the simulation period in hours from the beginning of the current simulation.
- At fixed reference
Selecting this option allows the user to enter a specific date and time for defining the simulation period. This time represents the time at which the conditions of the system will be written to the Hot Start file. The software writes flow and stage at all of the computational nodes and the stage in all of the storage areas to the file.
- Additional restart files (every-OMIT? What is the purpose of this word?)
Alternatively, the user can select this checkbox to write multiple restart files from a single run. On selecting this checkbox, the user must enter the number of hours between subsequent writes of the file.
- Write Initial Conditions Restart File At Simulation End
Selecting this checkbox causes the software to write the last step as a separate restart file.