Calabazas Creek Regional Park and Open Space Preserve
Sonoma County Regional Parks
Introduction
Calabazas Creek Regional Park & Open Space Preserve is located in southeastern Sonoma County, approximately 7 miles north of the town of Sonoma and 10 miles southeast of the city of Santa Rosa. The Preserve extends from the low-lying eastern edge of Sonoma Valley upward toward a prominent ridge top of the southern Mayacamas Mountains, near the longitudinal center of California’s Coast Ranges geomorphic province.
Sonoma County Regional Parks is making minor improvements to the existing trails and parking area, and installing informational, directional, and regulatory signage to facilitate interim public access.
As part of fully opening a new park, Sonoma County Regional Parks must complete a master plan to guide the development of trails, recreational and educational uses, and stewardship of cultural and natural resources, a process which typically takes three to five years. Sonoma County Regional Parks has proceeded by requesting, accepting and evaluating qualified consultants to provide support in development of the master plan and California Environmental Quality Act (CEQA) studies. The master plan process will include extensive community engagement and feedback to inform a comprehensive vision for the future of the property.
Environmental Resources
Water Resources
Calabazas Creek is one of the principal drainages that flow westward from the county divide into Sonoma Creek. It is the second longest among Sonoma Creek’s tributaries, after Agua Caliente Creek.
The headwaters of the creek are on the property and all of the surface waters on the Preserve, from ephemeral swales to seasonal tributaries, drain into Calabazas Creek, such that a self-contained sub-watershed is contained within the Preserve boundaries. The fact that the majority of the main channel conducts water throughout the year, and supports a large number of deep pools (from a few inches to several feet) along most of its length, is evidence of the considerable amount of water conducted within the sub-watershed.
In addition to Calabazas Creek, the Preserve encompasses seven named seasonal streams, several of which support perennial pools and riparian vegetation along much of their lengths, as well as many more un-named seasonal streams and ephemeral drainages
Another notable aspect of the Preserve’s hydrology is the presence of a large number of springs and seeps, which result from the downward percolation of water being re-directed by impervious sub-surface bedrock to hill slope surfaces. In a few cases, the discharge is in the form of running water (springs), but mostly the features are simply moist or saturated (seeps). The streams, springs, and seeps support riparian vegetation that is an important habitat element for terrestrial wildlife and riparian associated birds. They also support a variety of aquatic or primarily aquatic species, including the special-status steelhead trout (Oncorhynchus mykiss) and foothill yellow-legged frog (Rana boylii).
The largest cause of disturbance to the creek network is roads. Soil erosion from poorly designed or maintained roads will lead to water quality and habitat deterioration. The second most important threat to water quality and habitat conservation is water diversions, which can cause inadequate flow to support riparian and wetland habitats and/or aquatic wildlife.
Geology
There are two geologic formations mapped on the Preserve — the Western Sonoma Volcanics that occur throughout most of the site, and a limited exposure of the older, underlying sedimentary Neroly Formation within the central and southeastern portions of the site.
Special-status Animals
Special-status animal species documented on the Preserve during reconnaissance wildlife surveys include:
- steelhead trout (Oncorhynchus mykiss) (Federally Threatened)
- northern spotted owl (Strix occidentalis caurina) (Federally Threatened; candidate for State listing)
northern spotted owl
- American peregrine falcon (Falco peregrinus anatum) (California Fully Protected Species)
American peregrine falcon
- Nuttall’s woodpecker (Picoides nuttallii) (USFWS Bird of Management Concern)
- foothill yellow-legged frog (Rana boylii) (CDFW Species of Special Concern)
foothill yellow-legged frog
- California giant salamander (Dicamptodon ensatus)
California giant salamander
Plant Communities
The dominant habitat types on the Preserve may be broadly classified as grassland, chaparral, mixed evergreen forest, and oak woodland. Additionally, several sensitive plants communities and sensitive habitats have been identified on the Preserve.
Grassland
Chaparral
Forests and Woodlands
Spring and Seep Wetlands
Grassland
Grasslands represent an important habitat type on the Preserve. The predominant grassland type on the site is introduced annual grasslands. While constituting only about 10 percent of the site (about 139 total acres), grasslands support plant and animal species that prefer or are endemic to this habitat type, and thereby add significantly to the overall site biodiversity. Some of the important grassland oriented animal species in the area include grassland nesting and foraging birds (including peregrine falcons and other foraging raptors), insects and other invertebrates, rodents, snakes, and lizards.
Chaparral
The chaparral habitat on the Preserve represents an important habitat (207 acres) component that should be protected and maintained. Chaparral provides unique wildlife habitat and supports three sensitive chaparral habitat types on the Preserve that are defined by three individual manzanita species — common manzanita, Stanford’s manzanita, and hoary manzanita. Chamise (Adenostoma fasciculatum) is the most abundant chaparral species on the Preserve, forming Chamise Chaparral on 99 acres.
Forests and Woodlands
Forests and woodlands, including Pacific Madrone Forest, California bay Forest, Douglas Fir Forest, Knobcone Pine Forest, and Oak Woodlands are among the dominant plant communities (935 acres) on the Preserve. They support a variety of native plant and animal species including some special-status species including Napa false indigo and northern spotted owl. Along the Calabazas Creek riparian zone there is 22 acres of Redwood Forest habitat.
Spring and Seep Wetlands
Aside from riparian corridors, wetlands on the Preserve are limited to areas around springs and seeps. Occurring along hill slopes that otherwise support upland habitats, these features represent conspicuous and unique habitats on the Preserve.
The following are the most common among springs and seeps within open grassland: Pacifi c rush (Juncus effusus ssp. pacifi cus), Davy’s centaury (Zeltnera davyi), tinker’s penny (Hypericum anagalloides), fringed willowherb (Epilobium ciliatum ssp. ciliatum), and the invasive pennyroyal (Mentha pulegium). Plants occurring among features within more wooded habitats giant chain fern, seep monkeyfl ower (Mimulus guttatus), and various sedges (Cyperus and Carex species).
Photo Tour
Calabazas Creek
Rock-hop stream crossing
Redwood Grove
Nunns Iron Spring Meadow
High Meadow
The Bowl
View from Ridge Trail
Calabazas Creek
Rock-hop stream crossing
Redwood Grove
Nunns Iron Spring Meadow
High Meadow
The Bowl
View from Ridge Trail
History of Calabazas Creek Open Space Preserve
Settlers and Homesteads
In the late 1800s, Anglo-Americans and European settlers introduced ranching, dairy operations, dry farming, and even mining (mercury, clay, rhyolite and opals) to the region. Perhaps one of the most famous former landowners was Mary Ellen Pleasant, former slave turned civil rights leader and San Franciscan entrepreneur. Pleasant purchased the land around 1890. She built a weekend retreat and named the property Beltane Ranch.
Mary Ellen "Mammy" Pleasant, a civil rights activist and abolitionist
