| Sonoma Creek | |
|---|---|
 Beaver dam on Sonoma Creek at Maxwell Farms Regional Park inSonoma, California, 2009 | |
  Location of the mouth of Sonoma Creek in California | |
| Location | |
| Country | United States |
| State | California |
| Region | Sonoma andNapa counties |
| Cities | Kenwood,Glen Ellen,El Verano,Sonoma |
| Physical characteristics | |
| Source | Bald Mountain |
| • location | 4 mi (6 km) southwest ofSt. Helena, California |
| • coordinates | 38°27′23″N122°30′25″W / 38.45639°N 122.50694°W /38.45639; -122.50694[2] |
| • elevation | 2,480 ft (760 m) |
| Mouth | San Pablo Bay |
• location | 11 mi (18 km) west ofVallejo, California |
• coordinates | 38°9′2″N122°24′13″W / 38.15056°N 122.40361°W /38.15056; -122.40361[2] |
• elevation | 0 ft (0 m) |
| Basin size | 170 sq mi (440 km2) |
| Basin features | |
| Tributaries | |
| • left | Calabazas Creek,Schell Creek |
| • right | Yulupa Creek,Asbury Creek,Dowdall Creek,Fowler Creek,Graham Creek,Bear Creek |
Sonoma Creek is a 33.4-mile-long (53.8 km)[3]stream innorthern California. It is one of two principal drainages of southernSonoma County, California, with headwaters rising in the rugged hills ofSugarloaf Ridge State Park and discharging toSan Pablo Bay, the northern arm ofSan Francisco Bay. The watershed drained by Sonoma Creek is roughly equivalent to thewine region ofSonoma Valley, an area of about 170 square miles (440 km2). The State ofCalifornia has designated the Sonoma Creekwatershed as a “Critical Coastal Water Resource”.[4] To the east of this generally rectangular watershed is theNapa River watershed, and to the west are thePetaluma River andTolay Creek watersheds.
This south flowingriver drains the western slopes of theMayacamas Range, the southern slopes ofAnnadel State Park and the eastern slopes of theSonoma Mountains with intermittent winter flows in the higher tributary reaches. As the tributaries and headwaters reach the valley floor, a perennial stream cuts through scenic and valuablevineyards ofKenwood. Sonoma Creek veers west at Kenwood and cuts agorge running parallel to Warm Springs Road, where it turns south to historicGlen Ellen, passing within one mile (1.6 kilometers) ofJack London State Historic Park and theWolf House and thence southward paralleling Arnold Drive. In the city ofSonoma it is anurban creek which emerges into agricultural areas to the south. Finally, Sonoma Creek discharges to the vastNapa-Sonoma Marsh at the northern tip of San Pablo Bay. Principal tributaries to the creek includeYulupa Creek,Graham Creek,Calabazas Creek,Bear Creek,Schell Creek, andFowler Creek.
Headwaters rise on the west facing slopes of the inner coast southernMayacamas Mountains, where the highest peaks areHood Mountain, elevation 2750 feet (833 m) and Bald Mountain, elevation 2729 feet (826 m), each of which has views of the Pacific Ocean and theSierra Nevada range. The headwaters cut throughgorge and meadow ofSugarloaf Ridge State Park, which boasts 25 miles (40 kilometers) of self-guidedtrails and theRobert Ferguson Observatory. There is also a 25 foot (eight meter) high waterfall, present only when fed by the winter rains but can persist until late June for high rainfall years such as 2006. In the 100 foot (30 m) deep gorge into which the waterfall spills is a moist mixed forest habitat includingCalifornia bay laurel,coast redwood,Douglas fir,big leaf maple, cherry holly,coffeeberry, and eventanbark oak. The understory features abundantferns and boulder ladenmosses. A prominentlandform in this upper reach created by Sonoma Creek isAdobe Canyon. Locally part of this upper reach flow is sometimes called Adobe Creek. Tributaries near the headwaters include Mount Hood Creek and Graywood Creek.[5]
A diversity ofaquatic andterrestrialorganisms populate Sonoma Creek and itsriparian zone. Winter-runChinook salmon (Oncorhynchus tsawytscha),Delta smelt (Hypomesus transpacificus) andsteelhead (Oncorhynchus mykiss) are the most prominentfishes.Anadromous fish movements in Sonoma Creek have been studied extensively not only in the mainstem Sonoma Creek, but in some of the tributaries. These investigations have demonstrated a historical decline in spawning and habitat value for these species, primarily due tosedimentation[6] and secondarily to removal of riparian vegetation since the 1800s.
A variety ofsalamanders,snakes andfrogs are also present. The federally listed as threatenedCalifornia red-legged frog is present in the northern reach draining the south slopes ofAnnadel State Park. Severalendangered species (mostly associated with the marshy discharge area) present includeCalifornia clapper rail (Rallus longirostris), Californiablack rail (Laterallus jamaicensis), Californiabrown pelican (Pelicanus occidentalis), California freshwater shrimp (Syncaris pacifica),salt marsh harvest mouse (Reithrodontomys raviventris ),Suisun shrew (Sorex ornatus sinuosus),Sacramento splittail (Pogonichtys macrolepidotus). The above are endangered species with the exception of the splittail, steelhead and black rail, which species are federally designated as threatened.
California golden beaver ("Castor canadensis subauratus") were historically abundant along Sonoma Creek but were trapped out in theCalifornia Fur Rush of the late eighteenth and early nineteenth centuries. In 1828 fur trapper Michel La Framboise travelled from theBonaventura River to San Francisco and then the missions ofSan José,San Francisco Solano andSan Rafael Arcángel. La Framboise stated that "the Bay of SanFrancisco abounds in beaver", and that he "made his best hunt in the vicinity of the missions".[7] The beaver were likely wiped out by the mid-nineteenth century but returned to Sonoma Creek, likely from theDelta, in the 1990s.[8] In 1996 a beaver family developed a taste for merlot grapevine bark in a vineyard beside the creek and were exterminated, leading to civic uproar and a shift to accommodate beaver resettlement. Sonoma Ecology Center executive director Richard Dale reports that although beavers fell trees and dam culverts, on balance they perform nearly "perfect stream restoration," because they cause the creation of deep pools, slowing the flow of flood water and enhancing fishery habitat.[9] New beavers have recolonized Sonoma Creek and are currently located in bothSonoma andGlen Ellen. A "keystone species", the beaver have created habitat that has, in turn, led to the return ofriver otter ("Lontra canadensis") which have been sighted recently in the beaver pond below the Boyes Boulevard bridge inBoyes Hot Springs.
Upland ecosystems drained include mixedCalifornia oak woodland,chaparral andsavannahwoodland, In these upland reaches one finds plentifulblack-tailed deer,coyote, skunk, raccoon, opossum,wild turkey,turkey vulture,red-tailed hawk and occasionally bobcat andmountain lion. Prominent higher elevation trees include:coast live oak,Garry oak,Pacific madrone,California buckeye,Douglas fir, whereasvalley oak is prevalent on theSonoma Valley floor.
Up until about 1850, Sonoma Creek was unchanged from its natural state. Adverseerosion and bank cutting were at sustainable levels and did not add enoughturbidity to the creek system to discourage aquatic species. Flooding in the downstream reaches did not realize the modern frequencies since all thecreek reaches could absorb more excess water from peak rainfall events. TheKenwood area existed in the form of a large marsh effectively blocked by a natural earthendam from penetrating the course of the creek as it flows west out of Kenwood towardGlen Ellen.
With the advent of more intensive farming of Sonoma Valley in the latter half of the 19th century, the KenwoodMarsh was drained in favor ofgrazing,vineyards and otheragricultural uses. This action removed the largest upstream buffer that assisted flood control in the lower reaches of Sonoma Creek. Consequently, the frequency and severity of modern floods (1960s onward) has been exacerbated by these interventions of humans.
In 1978, Sonoma Creek was named a historic resource by the Sonoma League of Historic Preservation for being "one of the most picturesque sites and valuable natural resources in Sonoma County."[10]
The State of California Regional Water Quality Control Board considers the most significantwater quality parameters in Sonoma Creek to be:turbidity,pathogens andnitrates. Turbidity is an issue because of historical problems of erosion of stream banks, especially in the presence of ongoing land development inSonoma Valley. Increasedsedimentation has a variety of adverse impacts including direct harm to aquatic organisms and the more specific impact of alteringstreambedgravels to reduce productivity of spawning habitats; additionally sedimentation of pools decreases the efficacy of anadromous fish summering habitat by increasing critical summer water temperatures in these pools.[6] Pathogens appear to be linked toseptic tank orleach field failures in some of the rural reaches, particularly in the upper valley sections. Nitrates enter the stream system from excess fertilizers applied to land uses in the drainage basin and may also be present in septic wastes improperly entering the creek. Sediment and nitrates may also enter the stream through urbanstormwaterrunoff in the city of Sonoma reach.[11]
Because Sonoma Creek is the sole drainage flow of theSonoma ValleyWine Country, it is a vital resource foraquifer recharge. Proportionally a greater percent of Sonoma Creek feeds recharge than its neighbors, theNapa andPetaluma Rivers. This outcome derives from the presence of pervious valley flooralluvial soils and the gentle stream gradients along the valley floor, where most of the reaches occur. The valley itself is part of theFranciscan Complex, which includes crumpled, upliftedterranes that have resulted from thesubduction of the former oceanicFarallon Plate under the North American continent. The area is attended byvolcanism and sediments, deposited in the lagoons behind itsisland arcs, which resulted from geological events dating from 140 to 42 million years. Recharge for the Sonoma Valley is critical because local rainfall is only about 29 inches (74 centimeters) per year. Grape growing andwine production require considerablegroundwater extraction, and there is controversy over wineries use of annual creeks and waterways.
This large marsh area has been reduced considerably from its historic dimensions due to construction of multiplelevee systems and encroachment byagriculture and other forms of development. ThisNapa-Sonoma Marsh has been formed largely bysedimentary deposits over the last two million years. The basement depositional layer is theAlameda group. Higher are Oldbay mud and Young bay mud, between which there are intermediate deposits of theAlameda formation, which consists ofalluvial andswamp origins. The entire marsh area is considered subject toliquefaction in the case of a majorseismic event.[12] Themarsh is subject to diurnaltidal variations of approximately 5.5 feet (1.7 m).
Historically the marsh supported an extremely diversewetlandsecosystem, with a variety of primary productivity plants includingpickleweed,eelgrass and giant bulrush (Scirpus californiens). There has also been historically significant fish,mammal,amphibian and avafauna. The marsh is a significant element within thePacific Flyway providing resting and feeding areas formigratory birds. As of 2006 this ecosystem has been significantly compromised by fill,levee formation,dredging and other development; estimates generally state that 75 percent of the original biological productivity of the marsh has been destroyed. However, it remains a significant habitat and is subject to meaningfulwetlandrestoration activity, that is being actively evaluated as of the 2000–2006 timeframe.[13]
Because of the recognition of impacts of land development and land use practices, which began in the mid-19th century and have continued until 2006, certain actions are being considered[14] by the Board of Supervisors of Sonoma County. Most notably a specialparcel tax may be submitted to voters to assess landowners adjacent to Sonoma Creek. These funds could be used inflood control,hydrology modeling studies, stream conservation work, including erosion control andwildlife conservation. Other current activities include considerable research in public and private sectors including work by the U.S. Army Corps of Engineers, Sonoma County and various private conservation groups.
Due tooverpopulation ofSonoma Valley as well as overly intensiveagriculture,groundwater supplies have been drawn down to the point of causing deleterious effects.[15] TheU.S. Geological Survey has found in theCarneros region between Sonoma Creek and the Napa Ridge that due to excessive groundwater drawdown,saltwater intrusion is already occurring, rendering water unsuitable for many uses.
