If you have a short pipe and an significant offset depth for the pipe at either the upstream or downstream end of the pipe then the difference between the arithmetic method of calculating the slope and the SWMM 5 method can be noticeably different.
If you have a short pipe and an significant offset depth for the pipe at either the upstream or downstream end of the pipe then the difference between the arithmetic method of calculating the slope and the SWMM 5 method can be noticeably different.