Modeling Options

[MLee]

I am struggling to find the appropriate modeling approach for my situation. I have a stream running into an undersized culvert. The excess flow overtops and flows over land into an adjacent watershed. Should this be modeled with split flow, with a lateral structure or how?

The first photo shows the (1) upper reach, (2) cross-section/junction “overflow 1”, (3) lower left reach, (4) culvert/lower right reach, and (5) downstream endwall/cross-section.

The second photo is an enlargement of the first. The numbers represent the same items as the one above.

[Lonnie A]

If you are needing to map the overflow you probably need to have a reach covering the area that receives the overflow. If you are just needing to reduce the flow on the structure by diverting the overflow, a lateral would work. You may want to investigate using 2D to help with setting up a pure 1D model if that is the end model required.
Attached is a couple examples of how in the past I’ve handled modeling what I envision your situation to be.

lateral_weir_usage_tips.pdf

[Anonymous]

Thanks Lonnie. I will give it a try.

[Anonymous]

I have set up a Lateral Weir Embankment Over Multiple XS’s, where under-sized culverts cause headwater backup to upstream cross-sections. I ran the Steady Flow Analysis on the 1D model Optimized with the excess tailwater flow going Out of the system.

1. In the Lateral Weir Embankment editor, I completed all entries, except the Weir Stationing at TW XS’s, where under the RS column it says “Upstream TW RS needs to be set on LW Editor.” Where do I find the LW Editor?

2. In the Levee Breach Data editor, I just entered the Center Station, Final Bottom Width, the Left and Right Side Slopes, and the Breach Weir Coef. (I did not enter the Final Bottom Elevation, Time, or Starting WS.) Is any of this necessary for my 1D model?

3. When I run the model, it reports “FLOW OPRIMIZATION FAILED TO CONVERGE, PROFILE 1”. Is that because I sent the excess tailwater flow Out of the system?

4. The flow down through the reach does reduce according to the profile output table. The downstream flows appear to be exactly what I expect to remain, but does not add to the downstream flows from the Steady Flow Data. How do I reflect the additional flow downstream?

[Author]

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