Environment, Coasts, Oceans, & Infrastructure

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  • 1.  Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 05-28-2018 09:01 PM

    All,

    I'm looking for some concepts to reduce the gravel, sediment load coming into this existing struct, see attachments. During this high water season and lower seasonal flows we are seeing tremendous bed loading coming down this mountain stream.  As you can see the flow vectors are pushing the majority of material into the diversion channel.

    Removing the main channel stop boards allowed all of the material to clear out before spring runoff.  Stop boards were reinstalled and material filled back in over a 2-3 day period. Material plugs the sluice gate opening and we are having to clear it 2-3 times a day.

    Any comments will be greatly appreciated.

    Thanks,



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    Alan Shaw P.E., M.ASCE
    (406) 223-6223
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  • 2.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 05-29-2018 09:59 AM
    It'll take some r.o.w. but create a pond, even a relatively small one to drop the big gravel.

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    James Justin Mercier, P.E.
    Life Member ASCE
    Sr. Life Member IEEE
    Austin Texas
    512-442-4016
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  • 3.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 05-29-2018 10:52 AM
    Edited by Tirza Austin 05-29-2018 10:51 AM
    Hi,

    I'm not quite sure I understand from the pics which one is the diverted canal and which one is the continuing stream...

    If your problem is that the canal is taking in too much gravel, you can use a vortex gravel trap; that is simply a diagonal slot across the canal's bed, to be located in a sector with more or less uniform flow, that will return some flow to the river, with most of the gravel and coarse sand load.

    If the problem is gravel depositing around the intake, then I would probably try to install a judiciously-designed baffle upstream of the intake.

    Cheers, Claudio

    ------------------------------
    Claudio Meier Ing., M.ASCE
    Associate Professor of Civil Engineering
    University of Memphis
    Memphis TN
    (901)678-3158
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  • 4.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 05-29-2018 01:22 PM
    ​Alan,

    It appears as though there may be guides on the upstream wingwall.  Are weir boards installed?  Raising the effective invert at this location could exclude some of the larger material during high streamflows.

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    James Kapla P.E., M.ASCE
    Seattle, WA
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  • 5.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 06-01-2018 09:58 AM

    A lateral intake is often an appropriate design for diversion of flow from a stream or river transporting bed-load into a irrigation or power canal. The main principles are to flush bed-load past the structure while decanting relatively clean surface flow into the canal. These principles are often given in hydro-power handbooks but without providing necessary design parameters to guide design of a practical structure. I have attempted to identify suitable design parameters from study of various case study and project descriptions. I am attaching a pdf file with recommended guidelines. I hope these will help in designing suitable modifications to improve function of your structure. 



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    Philip Helwig P.E., M.ASCE
    PRINCIPAL
    St.John's
    1 709 7399643
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    Original Message


  • 6.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 06-04-2018 09:57 AM
    Edited by Tirza Austin 06-04-2018 09:57 AM
    Your attachment was most helpful in understanding what concepts should be considered.
    Thanks much.

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    Alan Shaw P.E., M.ASCE
    Belgrade MT
    (406)223-6223
    ------------------------------

    Original Message


  • 7.  RE: Irrigation Diversion Structure - Gravel, Sediment Load Reduction

    Posted 06-05-2018 03:03 PM
    Edited by Tirza Austin 06-05-2018 03:02 PM
    ​If you can reduce the velocity of the stream just above the intake, it will drop some of its sediment load - r.o.w. for a pond was suggested, deeper or wider may also accomplish the goal if you can do it without destroying your banks (consider filter fabric, interplanted rip rap).. at low flows, you might try a natural solution like a reed planting. It won't accomplish much at high flows but will survive them and give you improvements at steady state. Good Luck.

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    Lynne Baker A.M.ASCE
    Consultant
    HKA Formerly Hill International Consulting
    San Diego CA
    (858)832-8844
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