Today was really exciting at Lucas Creek. We built probably the first rock vane in New Zealand, maybe the southern hemisphere! Those of you who have accessed the NCHRP Report 544 or the ESenSS manuals (www.esenss.com) know that “REDIRECTIVE” techniques (Rock Vanes, Bendway Weirs, etc) are often cost-effective and environmentally-sensitive alternatives to ” RESISTIVE” techniques such as rip rap, gabions, automobiles, refrigerators etc.
The research commissioned by Transportation Research Board (NCHRP 544 / ESenss) compiled documentation that Vanes, for instance, produce a scour pool at the tip and slow water adjacent to the bank. This substrate complexity provides much more habitat, as several fish counts and bio-assays demonstrated.
What is really cool about vanes is they redirect the high flow velocities away from the bank. Two rock vanes can move the thalweg away from the bank 20% of the stream width. Therefore, with no impinging flows against an outer bend, the bank can be protected with more vegetative type measures. One vane will convert actively eroding banks into depositional areas both upstream and downstream of the vane!!!
Also, we got much of this weeks work area all “buttoned up” with Compost Blankets (2-3″ (50mm) thick) and some compost berm. Compost is not new here in NZ but this project gaining lots of attention so seeing the use of Compost Blankets (these are the “Eco-Blanket type), Compost Socks (“Living Walls”), Compost Silt Socks, and, my favorite alternative to silt fence, the Compost Berm should help with more widespread acceptance.
I’m reminding everybody here about the Caltrans sponsored research done in California and the new SSPs recently developed for Compost Blankets, Compost Socks, and Compost Incorporate ( see https://www.dot.ca.gov/hq/LandArch/ec/index.htm)