Flood Protection

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Flood Protection Zones
Zone Development and Funding
Central Sonoma Watershed Project
Spring Lake

Flood Protection Zones Back To Top

In 1958, under the authority of the Agency's enabling legislation, the formation of nine geographical zones, each encompassing a major watershed, was proposed as a means of financing the construction and maintenance of flood protection works within Sonoma County. The nine proposed zones include:

Zone 1A Laguna de Santa Rosa - Mark West Creek watershed
Zone 2A Petaluma Creek watershed
Zone 3A Valley of the Moon watershed (Upper Sonoma Creek)
Zone 4A* Upper Russian River watershed
Zone 5A Lower Russian River watershed (the Russian River from the mouth to Redwood Highway Bridge at Healdsburg, excluding Zone 1A)
Zone 6A* Dry Creek watershed
Zone 7A North Coastal watershed
Zone 8A South Coastal watershed
Zone 9A* Bay watershed (Lower Petaluma River and Lower Sonoma Creek)
*Zones not formed

Zone Development and Funding Back To Top

Over the succeeding several years, Zones 1A, 2A, 3A, 5A, 7A and 8A were officially formed. Zones 1A, 2A, and 3A have Zone Advisory Committees that annually prioritize and approve capital improvement projects for their respective zones.

In November 1986 and again in 1996, the electorate of Zones 1A and 2A authorized the levying of benefit assessments within these two zones for 10 years to augment funds received from general property taxes. Since 1986 these revenues have supplemented the property taxes received by Zones 1A and 2A.

The officially formed zones have financed the construction of flood protection and drainage facilities, the maintenance of natural waterways, the preparation of master drainage plans for areas subject to flooding, and erosion and sediment control activities. The zones have also financed the flood protection operation and maintenance activities of the Agency.

Central Sonoma Watershed Project Back To Top

The principal flood protection facilities on the tributaries of the Russian River comprise the Central Sonoma Watershed Project, which was constructed by the Agency in cooperation with the U.S. Department of Agriculture, Soil Conservation Service (now called the Natural Resource Conservation Service or NRCS). The work plan for this project was completed in 1958 and various components of this project were constructed over the ensuing 25 years. Project components included the construction of floodwater retarding structures and the straightening, shaping, and stabilization of waterways. The project alleviates flooding in the Santa Rosa urban area.

The Central Sonoma Watershed project includes five flood protection reservoirs that were built in the late 1960s to reduce flooding in the Santa Rosa area. These five reservoirs are:

Santa Rosa Creek Reservoir (also known as Spring Lake)
Matanzas Creek Reservoir
Piner Creek Reservoir (on Paulin Creek)
Brush Creek Middle Fork Reservoir
Spring Creek Reservoir

Spring Lake Back To Top

Spring Lake was constructed between 1961 and 1964 as a flood protection reservoir by the Sonoma County Water Agency. The project, which consists of three steel and concrete dams, spillways, channels, and flow regulators and represents one of the Agency's most ambitious flood protection projects, diverts floodwaters from Spring Creek and Santa Rosa Creek into Spring Lake, alleviating much of downtown Santa Rosa's flooding. The project is designed to accommodate water equal to a 100-year flood (in other words, a storm that, based on past records, has a 1 in 100 - or 1 percent - chance of occurring in any year.) Only once since the lake's construction, in 1986, has flooding been so severe as to exceed Spring Lake's capacity.

In 1974, the Agency began plans to develop the land surrounding the reservoir into parkland. Today, Spring Lake Park is one of the most popular recreation areas in Sonoma County. The park's 320 acres accommodate a 72-acre lake, a 3-acre swimming lagoon, and miles of walking, hiking, and horseback-riding trails. The park also includes a visitors' center, campsites, picnic areas, and boating facilities. Spring Lake Park is operated by the Sonoma County Regional Parks Department under a contract with the Sonoma County Water Agency.