Sonoma Creek

Sonoma Creek Spanish:Estero de Sonoma
Beaver damon 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	SonomaandNapacounties
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
• 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
• 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 Creekis a 33.4-mile-long (53.8 km)streaminnorthern California.It is one of two principal drainages of southernSonoma County, California,with headwaters rising in the rugged hills ofSugarloaf Ridge State Parkand discharging toSan Pablo Bay,the northern arm ofSan Francisco Bay.The watershed drained by Sonoma Creek is roughly equivalent to thewine regionofSonoma Valley,an area of about 170 square miles (440 km²). The State ofCaliforniahas designated the Sonoma Creekwatershedas a “Critical Coastal Water Resource”.To the east of this generally rectangular watershed is theNapa Riverwatershed, and to the west are thePetaluma RiverandTolay Creekwatersheds.

This south flowingriverdrains the western slopes of theMayacamas Range,the southern slopes ofAnnadel State Parkand the eastern slopes of theSonoma Mountainswith intermittent winter flows in the higher tributary reaches. As the tributaries and headwaters reach the valley floor, a perennial stream cuts through scenic and valuablevineyardsofKenwood.Sonoma Creek veers west at Kenwood and cuts agorgerunning parallel to Warm Springs Road, where it turns south to historicGlen Ellen,passing within one mile (1.6 kilometers) ofJack London State Historic Parkand theWolf Houseand thence southward paralleling Arnold Drive. In the city ofSonomait is anurbancreek which emerges into agricultural areas to the south. Finally, Sonoma Creek discharges to the vastNapa-Sonoma Marshat 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

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 Nevadarange. The headwaters cut throughgorgeand meadow ofSugarloaf Ridge State Park,which boasts 25 miles (40 kilometers) of self-guidedtrailsand 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 May 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 abundantfernsand boulder ladenmosses.A prominentlandformin 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.

Ecology

A diversity ofaquaticandterrestrialorganismspopulate Sonoma Creek and itsriparian zone.Winter-runChinook salmon(Oncorhynchus tsawytscha),Delta smelt(Hypomesus transpacificus) andsteelhead(Oncorhynchus mykiss) are the most prominentfishes.Anadromousfish 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 tosedimentationand secondarily to removal of riparian vegetation since the 1800s.

A variety ofsalamanders,snakesandfrogsare also present. The federally listed as threatenedCalifornia red-legged frogis 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 Rushof the late eighteenth and early nineteenth centuries. In 1828 fur trapper Michel La Framboise travelled from theBonaventura Riverto San Francisco and then the missions ofSan José,San Francisco SolanoandSan Rafael Arcángel.La Framboise stated that "the Bay of San Francisco abounds in beaver", and that he "made his best hunt in the vicinity of the missions".The beaver were likely wiped out by the mid-nineteenth century but returned to Sonoma Creek, likely from theDelta,in the 1990s.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.New beavers have recolonized Sonoma Creek and are currently located in bothSonomaandGlen 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,chaparralandsavannahwoodland,In these upland reaches one finds plentifulblack-tailed deer,coyote,skunk, raccoon, opossum,wild turkey,turkey vulture,red-tailed hawkand occasionally bobcat andmountain lion.Prominent higher elevation trees include:coast live oak,Garry oak,Pacific madrone,California buckeye,Douglas fir,whereasvalley oakis prevalent on theSonoma Valleyfloor.

History

Up until about 1850, Sonoma Creek was unchanged from its natural state. Adverseerosionand bank cutting were at sustainable levels and did not add enoughturbidityto the creek system to discourage aquatic species. Flooding in the downstream reaches did not realize the modern frequencies since all thecreekreaches could absorb more excess water from peak rainfall events. TheKenwoodarea existed in the form of a large marsh effectively blocked by a natural earthendamfrom 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 KenwoodMarshwas drained in favor ofgrazing,vineyardsand otheragriculturaluses. 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."

Water quality

Sonoma Creek in Kenwood during the 2021atmospheric riverandbomb cyclone.

The State of California Regional Water Quality Control Board considers the most significantwater qualityparameters in Sonoma Creek to be:turbidity,pathogensandnitrates.Turbidity is an issue because of historical problems of erosion of stream banks, especially in the presence of ongoing land development inSonoma Valley.Increasedsedimentationhas a variety of adverse impacts including direct harm to aquatic organisms and the more specific impact of alteringstreambedgravelsto 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.Pathogens appear to be linked toseptic tankorleach fieldfailures 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 urbanstormwaterrunoffin the city of Sonoma reach.

Wine production

Because Sonoma Creek is the sole drainage flow of theSonoma ValleyWine Country,it is a vital resource foraquiferrecharge. Proportionally a greater percent of Sonoma Creek feeds recharge than its neighbors, theNapaandPetaluma Rivers.This outcome derives from the presence of pervious valley flooralluvialsoils 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, upliftedterranesthat have resulted from thesubductionof the former oceanicFarallon Plateunder the North American continent. The area is attended byvolcanismand 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 andwineproduction require considerablegroundwaterextraction, and there is controversy over wineries use of annual creeks and waterways.

Discharge to San Pablo Bay

This large marsh area has been reduced considerably from its historic dimensions due to construction of multipleleveesystems and encroachment byagricultureand other forms of development. ThisNapa-Sonoma Marshhas been formed largely bysedimentarydeposits over the last two million years. The basement depositional layer is theAlameda group.Higher are Oldbay mudand Young bay mud, between which there are intermediate deposits of theAlameda formation,which consists ofalluvialandswamporigins. The entire marsh area is considered subject toliquefactionin the case of a majorseismicevent.Themarshis subject to diurnaltidalvariations of approximately 5.5 feet (1.7 m).

Historically the marsh supported an extremely diversewetlandsecosystem,with a variety of primary productivity plants includingpickleweed,eelgrassand giant bulrush (Scirpus californiens). There has also been historically significant fish,mammal,amphibianand avafauna. The marsh is a significant element within thePacific Flywayproviding resting and feeding areas formigratorybirds. As of 2006 this ecosystem has been significantly compromised by fill,leveeformation,dredgingand 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 meaningfulwetlandrestorationactivity, that is being actively evaluated as of the 2000–2006 timeframe.

Recent developments

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 consideredby the Board of Supervisors of Sonoma County. Most notably a specialparcel taxmay 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 andwildlifeconservation. 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 tooverpopulationofSonoma Valleyas well as overly intensiveagriculture,groundwatersupplies have been drawn down to the point of causing deleterious effects.TheU.S. Geological Surveyhas found in theCarnerosregion between Sonoma Creek and the Napa Ridge that due to excessive groundwater drawdown,saltwater intrusionis already occurring, rendering water unsuitable for many uses.

See also

• California slender salamander
• List of rivers in California
• List of watercourses in the San Francisco Bay Area
• Arnold Drive Bridge

References

Sources

• Lower Sonoma Creek Flood Management and Ecosystem Enhancement Study,Sonoma Resource Conservation District, 2012
• Sonoma Creek Watershed Management Plan, Sonoma Resource Conservation District2013

External links

• Napa Sonoma Marsh Restoration Project
• Sugarloaf Ridge State Park
• Sonoma Creek at Fish Friendly Farming
• Tidal Variations at Mouth of Sonoma Creek
• real-time measurements