After computing a model, one of the following messages is generated:
"There is no gutter leaving this 'On Grade' catchbasin. Bypassed flow is directed to the subnetwork outfall."
"The associated 'On Grade' inlet does not have a bypass gutter. The bypass flow will exit the system."Problem ID#: 65181
This means that the catchbasin inlet is set as on-grade but there is no downstream gutter link attached. In these cases, if there is bypass flow for the catch basin, or overflow from the subsurface network, this flow will be accounted as overflow volume. If you want the bypass flow to go to the elements downstream of the catch basin in question, you will need to add a gutter.
Note: When using the dynamic solvers such as Implicit and Explicit SWMM Solvers the overflow volume can be found under the Hydraulic Reviewer found under the Analysis Tab. Just select the node element (catch-basin, manhole) and run to see the overflow volume. See here to know how overflow volumes are handled by the dynamic solvers.
Note that in the event that this occurs and there is bypass flow with one of the dynamic solvers in SewerGEMS or CivilStorm, the catchbasin will present the bypass flow in the "Flow (Overflow)" field and will be accounted for in the overflow volume part of the mass balance. This will also flag the "Is overflowing?" as "true", even if the subsurface network's HGL has not reached the rim elevation.
Overflow reported at catchbasin even though HGL below rim elevation