Regardless of predictions, the Marin County Flood Control & Water Conservation District (District) prepares for every year as though it is an “El Niño year.” Although two major flooding years in Marin's history occurred during years with El Niño episodes (1997/98 and 1982/83), it is not unusual to experience major flooding in the absence of El Niño, such as in 2005/06. Flooding can even occur during a drought year such as last year, when the County suffered some of its worst flooding damage since 2006.
It is for these reasons that the District follows a consistent system of facility and creek maintenance each year which mitigates the risk of flooding. We conduct regular inspections of the creeks, floodwalls, and levees within our jurisdiction, and frequently test our pumps, motors, and generators. Creeks, drainage ditches, pipes, trash racks, and pump wet wells are cleared of vegetation, sediment, and trash in the fall and throughout the winter as needed. A flood control zone-specific update regarding maintenance, storm preparedness and response in your local area is provided below.
Pump Station Maintenance
There are no District-operated pump stations in Flood Control Zone 9 – Ross Valley.
Vegetation maintenance is performed as part of the annual stream maintenance program. See this web page for more information.
Localized sediment removal is performed by the cities and towns in Ross Valley where they have right-of-way and on an as-needed basis. Sediment removal is also performed by the District within the fish resting pools located along the bottom of the Corte Madera Creek concrete channel. A feasibility study is currently underway to evaluate sediment management within the lower reach of Corte Madera Creek partially located within the City of Larkspur.
Levee/Floodwall Maintenance & Rodent Control
The Corte Madera Creek channel is inspected every other summer by the U.S. Army Corps of Engineers and District staff, including during the summer of 2017. Patching of the concrete channel is conducted by county staff and/or contractors as needed. Each year, staff inspects, cleans, greases, and repairs as necessary the tide gates on the pipes that penetrate the channel wall.
Precipitation and Stream Gauge Maintenance
The District owns several precipitation and stream gauges throughout Marin that help inform us of heavy rainfall and water levels in creeks in real-time. The District-owned rain gauge in Ross Valley is located in Kentfield and there is a District-owned stream gauge on Corte Madera Creek in the Town of Ross. For more information on the gauges visit: https://marin.onerain.com/home.php.
Preventative maintenance on the gauges is performed twice annually - in Fall and Spring - and as needed. A grant was recently awarded in 2017 to install additional rain and stream gauges, and to upgrade the gauge software. This work is expected to be underway in 2018 after the rainy season.
The Town of San Anselmo and Ross Valley Fire Department own and maintain separate rain and stream gauges and web cameras that can be viewed on their website. They also provide a link to the above District-owned stream gauge in Ross to complement their stream gauge information network.
Before, during, and after storms, the Conservation Corps North Bay inspects and clears facilities as needed. They are also available for sandbagging and/or tarping levees and creek banks if requested. The District has a fleet of portable pumps that are maintained and tested prior to the winter season and some are pre-deployed in key locations.
The District is evaluating and has received a bid for temporary removable flood barriers that could be deployed quickly and in lieu of sandbags at flood threatened locations. The barriers are made of high strength plastic and achieve their stability by filling them with water.