On May 16, from 7 p.m. to 9 p.m. at the Community House, the Topanga Creek Watershed Committee (TCWC) presented “Stream Banks and Stream Reinforcement.” Using slides and case studies, Restoration Ecologist R.C. Brody, and Casey Burns, Biologist from the National Resource Conservation Service (NRCS), presented an informative talk on stream dynamics, regulatory issues surrounding encroachment into stream courses and environmental alternatives to hard-armoring stream banks (“bioengineering”).
Brody began the presentation with a discussion about how streams function, including their natural “desire” to form a serpentine series of curves, rather than just flow in a straight line. Certain conditions, often man-made, can cause a stream to be especially erosive, known as “hungry water.”
Casey presented the second part of the presentation, which focused on traditional stream-bank armoring versus bioengineering. Old-school stream-bank protection, familiar to many streamside Topanga residents, uses materials like concrete, rock rip-rap, cinderblock bricks and stone-filled gabions to protect the bank from erosion. Often, these materials become undermined and fail; they can also accelerate erosion downstream and upstream. In contrast, bioengineering uses materials such as living plants, often willows, to stabilize the bank. When installed properly, willow stakes, brush-bars and willow mats are stronger and longer-lasting than hard materials.
A lively group of Topangans attended, who had many questions for the presenters. Casey Burns is now stationed two days a week at the Resource Conservation District office in Malibu, and is available for free advice on stream- bank repair. Stay tuned for the next presentation by the TCWC.
For more information contact Casey Burns, Biologist, NRCS at (805) 386-4489; R.C. Brody, Restoration Ecologist, Impact Sciences at (805) 437-1900 or visit the websites, http://www.nrcs.usda.gov or http://www.trcr.bc.ca/docs/2002-polster.pdf.