Hec-Ras Flow Splitting Question 1

[TheEnginerd]

Hello,
I am currently using hec ras 4.1.0 and am having a difficult time determining the best way to model my situation.
I have a Reach (call it Swale 1) which ends at a HW where water can either enter a 36" pipe or fill up and over into an overflow swale.
Currently i have setup 3 reaches with a junction in the middle.
Reach 1 (upstream swale)
Reach 2 (overflow swale)
Reach 3 (pipe flow, modeled using Lids and preissmann slots)

The model won't run unless i give flows for Reaches 2 and 3. Is there a way that Hec-Ras can determine what the maximum capacity of Reach 3 is so that it can determine what the overflow into Reach 2 is? Should i be modeling this a different way, such as treating Reach 3 as a distributary?

thanks in advance

andy

 

[cvg]

model the flow into the overflow as a lateral structure

 

[gbam]

if you are treating this as a junction, the flows will adjust with each iteration as long as you have it triggered.

As cvg mentioned you can model it as a lateral weir.

If you are using a 36" pipe the discharges must be relatively small. Can you model it externaly (without RAS)? Just set up a rating curve at the inlet to the culvert and split the flow manually.

 

[TheEnginerd]

thanks for the advice. sorry for my delayed response.

i'm not sure how to TRIGGER the junction.

i like the idea of modeling this as a lateral weir. i understand how to model the lateral device it so that the flow from the lateral is tied to the second (downstream swale) at whatever station you like however it still asks me to for an initial flow for the downstream swale!! i wish the flow for the downstream swale was just the flow over the lateral structure, and that's all.