Welcome to the RAS Solution Forums HEC-RAS Help Modelling Drop in culvert

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  • #6596
    Anonymous
    Guest

    Hi everyone,

    I need to model an irregular shape culvert in Hecras. There is an inclined drop in the middle of my culvert. How can I model it in Hecras? Can I use cross section with lid?

    #10837
    Jake G
    Participant

    Hi Mike,

    In a similar situation, I modeled it as two separate culverts in series. The upstream section of the culvert was modeled with an entrance loss, but no exit loss, while the downstream culvert section was modeled with no entrance loss, but with an exit loss.

    The cross section in the middle of the culverts can be modeled with a lid.

    – Jake G.

    #10838
    Igloo_79
    Participant

    I am unclear about where XS with Lids should be used (as opposed to Bridges or Culverts). For instance, in this situation, couldn’t they be used for the entire structure, instead of modelling 2 culverts with XS inwith lids inbetween? What would be the pros/cons of the 2 approaches?

    #10839
    Anonymous
    Guest

    As far as I remember, It is better to use XS with lid for modelling long culverts. Culvert option in hecras is good for modelling short culverts. I have modeled the culvert with drop with cross section and lid but my model is unstable. I am thinking it might be better to model the culvert as XS with lids and the drop between them as inline structure. Do you guys have any suggestion?

    #10840
    Igloo_79
    Participant

    Hi – yes, it seems that XS with Lids would be preferable for long culverts and/or where there is are changes in culvert profile. I tried modelling a 42m culvert using lids but got a crazy spike in WS elevation: http://hec-ras-help.1091112.n5.nabble.com/XS-with-Lid-very-high-water-surface-profile-td4426.html

    Has anyone had similar issues?

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