Hello Liaqat,
I'm not too familiar with a leaping weir configuration, but if it is similar to Figure 8-3 in the blog article below, I would model it as a
[list]
[li]small orifice element representing the "diversion to interceptor" connecting to the dry weather effluent pipe[/li]
[li]weir element representing the "transverse weir" connecting to the wet weather effluent pipe[/li]
[/list]
I'd put the small orifice at a lower elevation than the weir crest elevation. Assuming the leaping weir (below) is what you're aiming for, this modeling method would result in some small erroneous flow into the dry weather pipe (probably minimal compared to the size of the wet weather flow).
https://swmm5.org/2016/09/05/example-8-combined-sewer-systems-from-epa-swmm5-applications-winfoswmm/
From your graph, I'm guessing the dry weather pipeline intake must be located strategically so that the water jumps over the intake at high flows, like in the blog post below. I don't believe such momentum-based characteristics of the water flow work so well in the simplified hydraulic modeling world...super-elevation is a similar effect that requires a more advanced modeling engine if you absolutely need to model it. Assuming you have the RTC module, you could force the diversion using MOUSE's RTC to set controls on either some valve elements, gate elements, or a weir height above a certain flow or above a certain level. This strategy would be fairly cumbersome and probably require quite a bit of iteration. You'd also need to add rules to the RTC to "reset" the configuration of everything back to dry weather conditions.
http://swmm5.posthaven.com/swmm-5-leaping-weir-example
If you don't have RTC, there may be a way to force the diversion to happen using passive controls in the link elements.
This is all assuming you're using MOUSE...if you're using SWMM I'd probably use some of the strategies in the referenced blog links above.
Hope that helps a little.
Thanks,
Brian
