March 30, 2010 § 2 Comments
The El Dorado Nature Center’s stream flows again! The City and construction team, led by Bubalo Construction, completed the regrading of the stream, protecting the banks with a mix of coir fabric and in places of high traffic, stone retaining walls. Willows staked into the coir will grow into trees, stabilizing the banks with their roots. « Read the rest of this entry »
December 28, 2009 § 2 Comments
Down in Long Beach, streambank stabilization continues. The Friday before the Christmas holidays, Drew Goetting of Restoration Design Group (in other words, my boss) flew down from Berkeley to train folks working at the El Dorado Nature Center on the process. Following is a little photo essay on making a willow wattle, for example.
The running joke was how much it was like making sushi. You lay down your fabric (or seaweed) in a little trench, put in the willow and soil (or rice, fish, avocado…) and roll it up. Two big exceptions to the analogy: the wattle needs stakes (we used live willow posts that will sprout into trees) and the sushi roll tastes better.
Soil bioengineering techniques like this have been used for centuries, and have found a resurgence in rural areas of America, as well as in some urban restorations in Northern California. Willow has long been observed to have tenacious roots that provide natural armoring of streambanks. And while the roots are strong, the trees themselves are flexible: if they fall over in a large flood, they form a layer that also protects the banks. But it is important to understand the dynamic interplay between a stream’s structure and how it functions, or forms its channel, however, in order to place these treatments correctly.
Stream restoration projects installed a couple of years ago at the Mountains Restoration Trust (Dry Canyon Creek) and (to a lesser degree) on Las Virgenes Creek also used forms of streambank soil bioengineering – proving that it has applicability here in Southern California.
November 2, 2009 § Leave a comment
Here’s a link to a project I’m working on, a rehabilitation of the artificial stream at the El Dorado Nature Center. Sharon Gates with the City of Long Beach is maintaining the project blog to keep the faithful nature center visitors up-do-date on the goings-on in the stream – the area being fenced off for public safety during the construction. Check out the progress!
The project will be using soil bioengineering techniques like willow postings, willow wattles, etc to stabilize some of the banks that have been subject to erosion over the years. Small areas will use rip rap or logs to shore up the banks where there’s a lot of foot traffic up to the edge – we want to keep this to a minimum and emphasize the ability of willow and other native riparian plants to hold a waterway’s banks. Huge quantities of the invasive Brazilian Pepper Tree have been removed, allowing in sunlight which will help the willow take root.
A lot of folks don’t realize the stream is artificial. The historical condition of the Nature Center area was likely a periodically inundated alkali meadow or fringe area of the wetlands that today are concentrated around Los Cerritos. Today’s Nature Center provides habitat for lots of birds, turtles and some mammals (including a coyote, I have heard).
My role in the project is pretty small – Restoration Design Group has me doing some construction administration, answering questions about design intent for the City and contractors, Bubalo Construction, who are implementing the project as a design-build.