San Rafael, CA – With California’s annual Flood Preparedness Week underway, it is important to remember to prepare for the worst. Despite the low rainfall in Marin County during winter 2017/18, it is impossible to know how intense this winter’s storms could be. Since early summer, the Marin County Department of Public Works (DPW) has conducted annual preparations across the region that are crucial for flood mitigation and stormwater drainage.
County Public Works collaborated with the Conservation Corps North Bay to remove fallen trees that were blocking flow in Warner Creek, a tributary to Novato Creek. “When there’s an imminent storm on the horizon, we usually get asked what we’re actively doing to prepare for it,” said Tony Williams, DPW Assistant Director and acting head of DPW Flood Control Division. “But by that time, generally we’ve been finished with the prep work for months. Storm preparations are a big undertaking and need to be conducted well ahead of storm season. We hope that’s comforting to the public.”
Storm season preparations, which are conducted every summer and fall, cover a wide range of work on creeks, levees, tide gates and pump stations. Tasked with this responsibility in parts of Marin, the Marin County Flood Control and Water Conservation District identifies issues and manages improvements in eight flood control zones across Marin. The zones do not cover the entire county and are, for the most part, concentrated in the county’s eastern urbanized corridor. The District oversees 44 miles of natural channels, 3.5 miles of flood control channels and 8.18 miles of levees.
Each summer, the District inspects 43 pumps housed at 17 stations across Marin’s watersheds to ensure that they are functioning at optimal efficiency. The pumps play an essential part in flood reduction for neighborhoods such as Tiburon’s Strawberry Circle and Bel Aire, Santa Venetia, lower Tamalpais Valley and Novato, where these pumps allow detention and bypass pumping of water during storm events.
The District coordinates with DPW’s Building Maintenance and Fleet Operations divisions to complete annual service requirements on all pump stations, including wet wells, electric motors and natural gas engines. The District also performs major maintenance for each pump on a six-year cycle, which includes full extraction and cleaning of the machinery. Over the summer, seven of the 43 pumps received their six-year major maintenance protocol.
Pump stations in the county transport stormwater from low-lying lands into creeks, facilitating natural water flow out to San Francisco Bay. Summer creek maintenance is a major part of storm preparations to maximize that flow. The District works with local agencies, such as Conservation Corps North Bay, and municipal public works departments to handle maintenance on 18 creeks across the eight watershed zones.
Teams perform essential vegetation management along creek banks and remove obstructions such as dead trees across the channel and man-made debris to maximize flow capacity. Over 20 creek projects were completed over the past six months, and significant obstruction clearing was conducted on Novato Creek and many of its tributaries, as well as Easkoot Creek in Stinson Beach and Reed Creek in unincorporated Mill Valley.
Sediment removal from creek beds is important for maximizing proper waterflow during a storm. District teams inspect creeks systematically to determine if sediment is reaching a level that needs to be addressed. The removal process does not need to be conducted annually and some creeks go several years without significant buildup. However, the sediment levels at Easkoot Creek in Stinson Beach and Coyote Creek in Tam Valley necessitated removal projects over the past year.
The District and DPW crews inspect, maintain and repair levees as part of the overall storm prep protocol. Over the past year, standard maintenance was conducted on levees in the areas of Richardson Bay, and Ross Valley, as well as the Timber Reinforced Berm system and levees in Santa Venetia. The standard protocol includes inspection for levee weak points, fortifying with supportive material and filling rodent burrows to prevent leaks during the wet season. Additional reinforcement and stabilization work was conducted on 2,688 linear feet of the Lynwood levee on Novato Creek, near the Vintage Oaks shopping center. The District also performed maintenance on two U.S. Army Corps of Engineers concrete channel projects over the summer, one at Corte Madera Creek in Ross Valley and the other at Coyote Creek in Tam Valley.
Roadway work, handled by DPW’s Road Division, is an important part of storm season preparedness. Annual practices require inspecting and cleaning roadside storm drains using a process called vactoring. Conducted in early fall, the process removes debris buildup and reduces the chances of clogging during storms. Compared with other areas of Marin, Tamalpais Valley and Santa Venetia require significantly more extensive vactoring because of their low elevation and propensity for flooding. The vactoring process is also used by District crews to clear out debris buildup in the wet wells at the pump stations.
There are hundreds of roadside drainage ditches along arterial and rural roads in unincorporated Marin, and those require attention as well. Sir Francis Drake Boulevard, Point Reyes-Petaluma Road, Novato Boulevard, Lucas Valley Road, Paradise Drive and Panoramic Highway were among those getting seasonal service. Upkeep on the ditches helps control stormwater flow and minimize roadside erosion. Hundreds of culverts, inlets and flow pipes are also inspected and, if needed, cleared along of all County-maintained roads.
During the fall months, roads crews sweep streets to keep debris out of drains and creeks. They use two large street-sweeper trucks and run routes across areas of unincorporated Marin with the densest concentration of trees along the neighborhood streets of Loma Verde, Marinwood, Greenbrae, Kentfield and Tamalpais Valley.
Earlier this year, the District installed nine new weather gauges that monitor rain, wind and stream activity. The new equipment was funded in part by a California Department of Water Resources grant. This brings the total to 18 gauges across Marin, significantly boosting the District’s ability to predict potential, localized flooding events and use real-time data to respond in a more targeted manner. Overtime, the data will help develop designs for new flood mitigation projects.
Residents are encouraged to take action prior to the rainy season to help mitigate flooding of private property, including the clearing of dead leaves from rooftop gutters and storm drains. Dead foliage should be disposed of in compost bins, not left in street gutters to clog drainage systems. If you live in a flood-prone area, stocking some sandbags (available at most hardware stores) and learning how to properly use them can be a huge help if the stormwater starts rising.
To learn more about storm preparations, visit DPW’s FEMA resources webpage or Marin Watersheds' flood preparedness webpage.