Problem

The following User Notification appears when attempting to compute a model, referring to either a pond or a conduit:

"Elevation-flow-volume table data overtopped...routing results invalid"

Or:

"Volume/Outflow data exceeded during routing"

Solution

If the flow through a pond or conduit exceeds the elevation/flow rating curve, the pond/channel has overtopped. In either case the results are invalid since the program doesn't have any information on the relationship between elevation and flow above that point. Because of this, a "capped" flat-topped (due to the overtopping) hydrograph will be passed to the next downstream element. Therefore, the results should indeed be reviewed, since surcharging conduits and ponds aren't handled.

To resolve this, either increase the size of the pond or conduit or review other input such as outlet structures and revise so that the pond does not overtop. If you need to quantify pond overflow, add another outlet structure (such as a large weir) to approximate the overflow and direct elsewhere.

For a conduit, if you expect it to flow full (for example an enclosed circular pipe), then consider setting the routing method to translation, or omit the conduit altogether since flow in = flow out for a full pipe. You can also consider using SewerGEMS or CivilStorm which can model surcharged pipes using the slot method.

See Also

How do I quantify pond overflow?