Creek celebration at El Dorado Nature Center

The newly re-made (man-made) stream at El Dorado Nature Center

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.

Streambank sushi

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 group surveys the toe of the stream and digs out a little trench to key in the wattle.

Woven coir fabric is laid out in the trench, with most of the fabric pulled temporarily into the channel.

Biodegradable “staples” or mini-stakes are driven into the ground to secure the biodegradable fabric.

Soil and willow get layered into the fabric.

Multiple layers of soil and willow get the wattle to just above the estimated height of the water.

The fabric gets pulled over and the wattle nudged into shape to test out if our “sushi roll” is full enough.

Satisfied that the wattle is big enough, the fabric is folded over and laid upslope on the bank.

More staples secure the top of the wattle’s fabric to the slope. Later, the space behind the wattle will get back-filled with soil.

Even our vendor of the coir fabric got into the action.

Live willow posts are driven into the center of the wattle. This provides anchoring of the wattle and also grows into trees that will be long-term stabilization of the banks.

Done! Only 2,390′ to go!

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.

Stream rehab down in Long Beach

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.