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    Sunday
    Dec262010

    9000 cfs ... whatever. Bring it on: A Geyersville Update

    Geyserville Bridge Project did great with HIGH WATER - 9000 cfs.
    Big storms hit Northern California last week.  There was a lot of fear and speculation about how the project would survive when the Russian River "ran really high".  Well, the "proof is in the pudding" as they say.  There have been a couple of big storms in December but the highest flows were encountered on the week just before Christmas.
    The rains started on Friday, December 17, and by 2:15 on December 22 the river peaked at an estimated 9250 cfs  (it was measured 7500 cfs at Cloverdale (9 miles upstream) and at 11,000 cfs at Healdsburg (6-7 miles downstream).  
    You can understand the concerns - how will some relatively "puny" rock vanes protect the highway and bridge during high water, when the vanes and longitudinal stone toe protection (LSTP) are completely overtopped?  Well, during this last storm the vanes, LSTP and our constructed floodplain bench were completely under 5-6 feet of water.
    The thing that is obvious from the series of photos here (captured from the Caltrans webcam at www.dot.ca.gov/dist4/128russianriver/) is that the flow velocities in contact with the bank were negligible.  No velocity, no tractive forces, no bank erosion.

     

    So, it looks like the thalweg management is working as planned.  
    Make a note that bendway weirs instead of rock vanes may have been an even better option for a river the size of the Russian.  However, given the constraints during construction (fish were soon to migrate, we couldn't excavate into the sandbars etc.) the rock vanes were a good choice.   It is really awesome to see the vanes working under that much water.
    For more information on redirective river training measures see NCHRP Report 544 and/ or ESenSS.     http://www.esenss.com/contents.htm
    Comments? Questions?  Let us know in the section below.

    

     

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    Reader Comments (3)

    It aint over till it's over

    Yogi Berra

    December 26, 2010 | Unregistered CommenterOld man river

    Very impressive! How much deposition along the bank do you anticipate in one season? With fluctuating water levels over the wet season, could there be a different type of erosion from bank saturation and slow pore drainage? Those banks are pretty high.

    December 27, 2010 | Unregistered CommenterJay Greening

    Hi Jay

    Yes the banks are sloughing off from primarily gravity and "sapping" (the increased pore pressure then drain down. I failed to mention that Caltrans has every intention of laying the banks bank to a more stable angle and vegetating them. But then the debate will be "is vegetation alone, even say the banks are 2:1, sufficient or do the upper banks need riprap. My philosophy is no rock slope protection (RSP) needed since there are no significant tractive forces. I think this is what the Resource Agencies are looking for also.

    December 30, 2010 | Unregistered CommenterJohn McCullah

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