Integrating Grazing into IPM for Flood Protection Facilities
Contra Costa County Flood Control and Water Conservation District (Contra Costa FCD) manages 70 miles of channels and 19 detention basins in the eastern San Francisco Bay area. Most of the channels are grass lined and run through a wide variety of suburban land uses. Many of the detention basins lie along the urban/wildland interface and provide important habitat for wildlife. Most of the stream facilities require grass lined channel vegetation which reduces stormwater flow resistance and allows for ease of inspection. Local fire department requirements also restrict the height of vegetation. Vegetation management of these channels historically consisted of herbicide applications and, in some cases, the use of riding mowers and gas powered vegetation trimmers. Increased regulations and pressure from passionate anti-pesticide advocates encouraged Contra Costa FCD to explore grazing as an alternative vegetation management technique.
Contra Costa FCD conducted a three year study comparing the safety, cost, and efficacy of herbicide applications with goat and sheep grazing. Vegetation, water quality, and erosion monitoring occurred at two reaches of Walnut Creek in Concord, CA. At the same time maintenance staff began using goats in a wide variety of flood protection facilities on a trial basis to evaluate logistics and cost.
Contra Costa FCD found all three methods had minimal impacts on water quality. Herbicide application alone did not meet most vegetation management goals, probably due to the build-up and change in type of vegetation from lack of vegetation management in previous years. Both sheep and goat grazing reduced far more vegetation than herbicides, but herbicides affected broadleaf plants more, allowing for grasses to dominate.
Grazing during the spring was cost prohibitive compared to herbicide applications and riding mowers, but was less expensive than the use of hand held weed trimmers. Grazing in late summer and early fall, when the operator of the grazing company was looking for pasture, was very affordable. Grazing allowed for easy access for vegetation management crews to target individual pest plants for spot applications of herbicides when they re-sprouted. Late summer grazing also removed vegetation just prior to annual inspection of streams, and exposed ground squirrel colonies, which could be eradicated. Grazed facilities removed cover for homeless encampments, and after the homeless had left, exposed trash and debris for easier removal. Grazing was also the best alternative in detention basins with high wildlife habitat value, as it was less disruptive to wildlife than mowing or disking, and was the favored vegetation management method by wildlife agencies.
Finally, the goats proved to be excellent ambassadors for Contra Costa FCD. Local TV and newspapers reported on the activity during the study. And grazing fits nicely into Contra Costa FCD’s efforts to be a steward of the environment.