Properly modeling Levees

[Anonymous]

Hello
I have a question regarding modeling levees within HEC RAS 4.1.0.

The stream I am modeling has a levee on one side with a large amount of agricultural area (5.5 square miles) on the opposite side of the levee from the stream. I have indicated the station and elevation of the levee using the levee option in the cross section window, however, when running a steady flow analysis, the levee is overtopped, and flows accumulate within the stream channel section, rather than being lowered as flow is diverted over the levee. It would seem that once the levee is overtopped, the higher flow elevations would be similar in elevation, rather than the elevations the program is generating (I am getting WS elevations up to 5-feet above the top of the levee surface within the main channel).

Can you please advise as to which function I should use to properly represent water surfaces within the channel after the WS elevation crests the levee?

Thanks

[Lonnie A]

Use lateral weirs to model the levee not the levee function in the XS editor. You’ll need to have the “flow optimization” under the steady flow window options selected.

[Anonymous]

Lonnie- thanks for the input, I am currently modeling the levee using the lateral structure function rather than the levee function in the cross section editor.

[Lonnie A]

if you turn on the optimization it should adjust flows

[Anonymous]

I have modeled the lateral structure (levee) in my model for a Steady Flow analysis, with flow optimization, and connected the lateral structure to a large storage area. However when I run the model, I still shows flows that appear to be too high within the channel in relation to the levee elevation. I tried the “linear routing” option, which models flow out of the system (accounts for a lateral structure without creating it in the model) and I get more realistic WS elevations. 50-, 100-, and 500-year flows at similar elevations near to the top of the levee elevation. Am I missing a step in conducting the Steady Flow analysis with lateral structure?

[Author]

Posts