In EFDC Model there is an option to choose the dynamic time step. The subroutine which controls the dynamic time step is CALSTEPD.f90. In this subroutine, there are four method check which determine the time step. They are as follows:
2) Method 2: Positivity of advected material.
3) Method 3: Implicit bottom friction and rotational acceleration damping
4) Method 4: Limit rate of depth change.
At the last, the minimum of the three methods is taken as the dynamic time step.
In EFDC Explorer, under run time parameters and EE Output Options there is an option for the dynamic time step: