San Rafael, CA – Despite the tinder-dry conditions in Marin County now, the local winters can be exceptionally wet, and serious flooding is a risk for parts of the community. With an eye on public safety during the traditionally rainy months, annual storm season preparations by the Marin County Department of Public Works and its contracted agencies have been completed across the region, a crucial job for flood mitigation and stormwater drainage.
County crews have worked with contracting partners the past several months to prepare creekbeds for storm season.
“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, Assistant DPW Director. “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 usually completed by 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 14 miles of levees.
Many areas of Marin are not within one of the flood control zones and therefore are not under the District’s supervision. The infrastructure not covered by the District includes state-maintained roadways such as Highways 37, 101 and 1, which are overseen by California Department of Transportation (Caltrans). DPW and District staff communicate with Caltrans to help strategize short and long-term solutions to ongoing flooding issues on Caltrans’ property, such as Manzanita Park & Ride at the Highway 101 and Highway 1 interchange and DPW’s research study of Highway 37.
Each summer, the District inspects 43 pumps housed at 17 stations across Marin’s flood control zones 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 the pumps transport stormwater from low-lying lands into creeks, facilitating natural water flow out to San Francisco Bay.
The District coordinates with DPW’s Building Maintenance and Fleet Operations divisions to complete annual service 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.
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.
Strategic sediment removal from culverts and road crossings 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.
The District and DPW crews inspect, maintain and repair levees as part of the overall storm prep protocol. Over the past year, standard maintenance including inspection for levee weak points, fortifying with supportive material and filling rodent burrows to prevent leaks was conducted on levees in the areas of Richardson Bay, and Ross Valley, as the levee system in Santa Venetia that includes the timber reinforced berms.
Roadway work, handled by DPW’s Road Maintenance 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 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. 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.
The District maintains 18 rainfall and creek flow gauges across Marin, helping predict potential, localized flooding events and providing real-time data to respond in a more targeted manner. In the long run, analysis of the data will help develop designs for new flood mitigation projects for the region.
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. Additionally, ReadyMarin.org provides many detailed resources, including emergency grab-and-go packing checklists, that can be helpful for residents to prepare for the unexpected.
It is important for residents to sign up for the Alert Marin notification system to be aware of emergency situations that could carry life safety implications, such as floods. The service, provided by the Marin County Sheriff’s Office, provides the public with time-sensitive alerts targeted toward specific addresses or neighborhoods. Residents who have registered should review their contact information to ensure it is up to date. Alert Marin is different from the Nixle service, which provides general public safety and/or post-disaster information.
Flood insurance is important for homeowners and renters alike, as it goes beyond what is covered under standard insurance policies. Even a few inches of water can result in thousands of dollars in repair and restoration costs. Marin County participates in the National Flood Insurance Program, which makes federally backed insurance available for all structures, and provides a range of resources to help property owners make the best decisions. Residents that seek such coverage are encouraged to contact their respective insurance agency but should be aware that it takes approximately 30 days to process, so advanced planning is advised.