SWMM56

Subject:    SWMM 5 and InfoSWMM Time Step Guide SWMM 5, H2OMap SWMM and InfoSWMM Time Step Guide by  dickinsonre Subject:      SWMM 5, H2OMap SWMM and InfoSWMM Time Step Guide If you use a variable time step in SWMM 5  or InfoSWMM/H2OMAP SWMM it is hard to gauge the proper value of the conduit lengthening.  You want to use a value that does not increase the volume of the network yet does increase the length of the shortest links so you can use a longer time step.  A good approximation to the time step that you want to use is shown in the image.   The  Time Step Guide  in seconds is  Link Length / [Velocity + sqrt(g*Maximum Depth)]  with the assumption that the velocity at maximum depth is about the value of the wave celerity for closed links or  sqrt (g*Maximum Depth).   Normally (unless pumps are involved) th...