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    Monday
    Dec132010

    Geyserville Bridge Project sees some High Water 

    Instant monitoring of project with Live Webcam is so cool!  Below is Todays Photo - 12-13-10 after last weeks flood waters overtopped project by 4 feet.!!
    Last week the North Coast got some significant rainfall and the Russian River rose as a result.  We have all been waiting to see how the Redirective measures - the 5 Rock Vanes we built and completed in October, will hold up when they are over-topped.  Well, the project did just great.  So far!!
    Chris Blunk, CT PE, reported that the river peaked at about 8000 cfs on Monday and reminds us that the 100 year flood is about 25,000 cfs.  He also reported 4' of water over the constructed floodplain terrace and "the thalweg is still right off the tips of the vanes".  Bob Blizzard, CT Inspector reported that the willows are growing.  We can thank Bob and Chris for some of the photos.  Also remember that the webcam is operational, so if you are interested in following the project tune into  http://www.dot.ca.gov/dist4/128russianriver/  and see for yourself!!   How cool is that, to be able to instantly monitor your project!!!

    Now remember, the intent of the project was to "move the thalweg stream-ward".  The big issue of secondary importance was trying/implementing the construction method of "Self-Launching" rock.  The emergency nature of the project and the environmental sensitivities were the primary design "drivers".  RSP (Rock Slope protection) - Rip rap in Caltrans jargon, would not be allowed by the Resource Agencies.  Other design constraints were water quality and both instream and gravel bar habitat protection.  In other words, we would not excavate the river bottom and we would not excavate the gravel bars.

    So, this was a perfect opportunity to utilize the self-launching (graded, poorly sorted) rock as described in NCHRP Report 544, and place clean rock on the existing river substrate.  This is how the Longitudinal Stone Toe Protection (LSTP doing double duty as the construction access road) was built.  And then the redirective Rock Vanes, attached to the LSTP, were installed to re-direct and manage the THAWEG.  So, if the thalweg and high energy stay away from the bank and out to the middle of the channel, then the project is a success.  See for yourself how it is working.

    David Derrick, upon seeing these photos commented " I like that thalweg".  I like it too, it is over 60' streamward of the bank and last winter the thalweg was at the toe of the bank.  Also notice in the photos the slow velocity and low energy of the flood waters over the terrace.

     

    Thalweg management, adding roughness (the willows, live siltation, live poles, and a flood bench), and a flood bench can sometimes replace RSP for an Environmentally-Sensitive approach to streambank protection.  please note that the vertical bank will be addressed in subsequent projects. 

    Any comments or questions out there?   Please use the comment bar and let us know what you think.

     

    John

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    Reader Comments (2)

    Looks great so far! The thalweg is close to the bank at the upstream end, but after the flow has to deal with the new roughness of the willows and starts working over the vanes, the thalweg ends up way out in the center and looks to be going directly under the bridge. The big test may be coming with this weekend's larger storm that is predicted. I think the US end looks most vulnerable, and I can't remember if you were able to install a vegetated key due to the vineyards... I predict that if the willows make it through the winter and form a dense continuous barrier with the established ones over the next summer, the site will become stable and require little maintenance.

    December 15, 2010 | Unregistered CommenterCharles F. Battaglia

    I am interested in access at this site for the public; paddlers, anglers, swimmers etc.. Can you tell me what the public easement is on each side of the bridge?

    April 21, 2011 | Unregistered CommenterS O'Brien

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