Stevens Creek

 

Vision 

Reservoir The Stewardship Plan for Lower Peninsula Watershed Area envisions the Stevens Creek subwatershed as a living stream with natural earthen channels that provide a reliable source of groundwater recharge, offer natural flood protection and support coldwater fish and other special status species. This vision of Stevens Creek also includes a network of natural and urban trails for the enjoyment of residents and visitors while preserving the lands surrounding Stevens Creek Reservoir from erosion and for source water protection. Key water resources features will be integrated into general or comprehensive plans or area-specific plans or zoning or other land use decision-making tools by five cities and the county; and community-based stewards will continue to protect and enhance water resources in the area.

Click here for watershed facts at a glance.

 

Potential Partners and Collaborators

In order to achieve this vision for Stevens Creek, the District works closely with municipalities and other agencies to preserve and protect the watershed through effective land use policies and programs.

The Stevens Creek watershed transects six municipalities: Cupertino, Los Altos, Mountain View, Palo Alto, Sunnyvale and the County of Santa Clara, each of which addresses water supply, flood protection and stewardship issues within their general plans. The District collaborates with these municipalities to ensure that overall goals and policies agree.

The District also partners and collaborates with community groups, including the Stevens and Permanente Creek Watershed Council; Friends of Stevens Creek Trail; and the Santa Clara Valley Audubon Society along with resource agencies and others. The District continues to partner with these entities in carrying out its mission.

In addition, the District collaborates with regional agencies and efforts such as the Habitat Conservation Plan (HCP), the Santa Clara Valley Urban Runoff Pollution Protection Program (SCVURPPP) and the South Bay Shoreline Study to ensure that projects and programs in Stevens Creek are in keeping with county-wide goals.

Working with partner agencies and the community, the District will implement or promote watershed-specific policies to preserve the integrity of the water resources features within the Stevens Creek watershed.

 

Watershed Maps

The interactive map below shows the location of the Stevens Creek watershed and illustrates some of the area's key features, such as major creeks, flood zones and groundwater basins.

To view key features, choose a layer from the "Select a layer to display" menu on the map below. You can select multiple layers to view at one time. Individual layers contain specific data that you can access by clicking on the layer itself.

 

 

 

Location and Natural Settings

Located in the western part of Santa Clara County, the Stevens Creek Watershed encompasses a 29-square mile portion of the Lower Peninsula Watershed Management Area (WMA). Stevens Creek is the longest creek in the Lower Peninsula, extending from the northeast slopes of the Santa Cruz Mountains to the southern tip of San Francisco Bay. One of the most “natural” creeks in the county, Stevens Creek contains significant stretches that are free from concrete channels. Rainfall in Stevens Creek drains northward into the Bay.

Eight other watersheds border Stevens Creek: San Francisquito, Adobe, and Permanente to the west; Sunnyvale West, Sunnyvale East, and Calabazas to the east; Baylands to the north; and San Tomas to the south.

The landscape of the Stevens Creek watershed corresponds to the overall topography countywide—relatively steep terrain transitioning to a flat valley floor. The Stevens Creek Reservoir divides the watershed into two areas, upper and lower, each with distinct features. In the upper area, the creek originates in the Santa Cruz Mountains at 2,500 feet and flows into the reservoir. It then runs downstream through more level terrain and urban areas before discharging into San Francisco Bay’s tidal basin.

The following photographs show Stevens Creek at various segments along its course:

 Sample photographs from Stevens Creek

 

Key Water Resources Features

The Stevens Creek watershed sits on top of the unconfined Santa Clara groundwater basin and connects to Permanente Creek via the Permanente Diversion Channel. Large portions of the upper watershed are highly susceptible to erosion and landslide, and managing water quality in Stevens Creek and the Reservoir to address impairments remains a challenge.

Reservoirs

The Stevens Creek Reservoir is the only District-operated reservoir in the Lower Peninsula. Constructed in 1935, Stevens Creek Reservoir holds 3,452 acre-feet or water, with a surface area of 475 acres when full. The area sounding the reservior is a part of the source water protection zone.

Major Creeks

Three creeks flow into the reservoir: Stevens Creek, Swiss Creek, and Montebello Creek. Stevens and Swiss Creeks run year-round; Montebello Creek is a seasonal creek that contributes streamflow mostly during the rainy season.

Aquifers

Stevens Creek sits atop of the Santa Clara Valley Goundwater Subbasin (basin), an aquifer in the northern part of the county with an estimated capacity at 350,000 acre-feet. 

Stevens Creek replenishes the Santa Clara Valley groundwater basin. The District also provides recharge through the Stevens Creek Pipeline. The pipeline crosses several creeks to allow instream recharge as well.

 

Watershed Health

Erosion

Stevens Creek has the highest erosion and landslide risk of all watersheds in the Lower Peninsula. Most erosion takes place in the steeper portion of the watershed east of Stevens Creek Reservoir. Areas of high erosion discharge sediment into the creeks, blocking flow and increasing the potential for flooding.

Flooding


In the early 1980's, an El Niño winter caused catastrophic flooding in the watershed. Since then, the Stevens Creek network was modified so that over 3/4 of the total creeks now have the capacity to convey water from a 100-year flood (i.e., a flood with a 1% chance of occurring in any given year). At highway interchanges and crossings, creek reaches were modified mainly for slope protection. To sustain this level of flood protection, land owners, cities, and the District need to work in concert to manage runoff and maintain the floodways.

The District employs natural flood protection wherever possible, which helps preserve the natural landscape and provides greater access to open spaces—important objectives for the District.

Water Quality Impairment

The US Environmental Protection Agency listed this creek as impaired for diazinon, toxicity, temperature and trash; the Reservoir impaired for legacy pesticides including chlordane, Dialdrin; Mercury, and Polychlorinated byphenyls (PCBs). Ultimately, a total maximum daily load for these contaminants will be established to improve water quality.

 

Environmental Stewardship

 

Riparian and Aquatic Habitat

Riparian habitats in the upper Stevens Creek watershed have remained much the same as they have been for decades—over 50% of the riparian corridor in the headwaters region is significantly forested. Species include oak, sycamore and eucalyptus. On the valley floor, increased development and changes in the creek structure have had a significant affect on the riparian ecosystem.

Aquatic habitats include areas of standing or flowing water that support aquatic wildlife, including amphibiens like red-legged and yellow-legged frog and the a range of fish species, including steelhead and rainbow trout, largemouth bass and bluegill sunfish. Numerous barriers create obstacles to fish migration and spawning upstream—over 110 impediments to fish passage exist in Stevens Creek, including seven that completely block access.

The segment between the Stevens Creek Reservoir and Highway 280 of the creek are a part of the collaborate agreement under Fisheries Aquatic Habitat Collaborative Effort that shares local water resources for steelhead trout and Chinook salmon that migrate from San Francisco Bay to spawn in Santa Clara County watersheds. About 619 million gallons of local runoff water are provided for fish habitat annually.

Trails and Open Space

The Stevens Creek watershed offers many parks and trails, and contains high quality riparian and aquatic habitat, part of which is designated as a cold water fisheries management zone by the Fisheries and Aquatic Habitat Collaborative Effort (FAHCE).

The reservoir supports a range of recreational activities for the public, including non-power boating, and mountain biking, hiking, horseback riding, and nature walks in the adjacent County park. Swimming is not permitted in the reservoir.

The high level of development in lower Stevens Creek presents a challenge for communities to identify opportunity sites for trails and open space. In order to create healthy, livable environments, the District collaborates with cities to protect riparian habitats, increase access to the creeks and provide more natural areas.

Projects

Projects such as the City of Cupertino’s Stevens Creek Restoration Plan (PDF) help increase access to the creek and improve connectivity. In this project, the City of Cupertino acquired 60 acres of land adjacent to Stevens Creek which they plan to restore to its natural alignment and enhance with trails, community parks and educational exhibits.

 

 

Browse the Draft Framework For Communicating Existing Interests

Related Plan Elements

ROLESTRATEGIES
District Has Primary Jurisdiction
E-3.1.1.2: Identify existing stream conditions and stream characteristics and implement practical solutions where appropriate, to improve stream stability and its dynamic equilibrium. (P)
District Advocates
E-3.1.1.3: Provide technical advice and, if appropriate, work with municipalities to manage stormwater to address stream flooding and environmental benefits. (T)
District Has Primary Jurisdiction
E-3.1.2.1: Maintain the design floodwater conveyance capacities within District-owned channels. (P)
District Advocates
E-3.1.2.2: Support and promote land use decisions to maintain stream capacity. (T)
District Collaborates
E-3.2.1.3: Assist municipalities and citizens when needed to lessen potential flood impacts. (C)
District Advocates
E-3.2.2.1: Assist in the incorporation of flood-wise design features (e.g., minimize imperviousness, preserve natural drainage, rain harvesting and provide flood water detention) within the watershed. (T)
District Advocates
E-3.2.2.2: Encourage and provide technical assistance in mitigating erosion, sedimentation and high flows from new development or redevelopments. (T)
District Has Primary Jurisdiction
E-4.1.1.1: Balance the protection and restoration of sensitive fisheries and aquatic species, such as steelhead trout, with a reliable water supply. (P)
District Collaborates
E-4.1.2.3: Engage in habitat conservation planning.(P and C)
District Has Primary Jurisdiction
E-4.1.2.4: Protect groundwater recharge areas in creeks and riparian corridors. (P)
District Collaborates
E-4.1.2.5: Protect, enhance and restore riparian vegetation and in-stream and tidal habitat conditions conducive to healthy ecology, including diked historical bayland wetlands, or former salt ponds. (P and C)
District Advocates
E-4.1.3.2: Promote the protection and preservation of sensitive groundwater recharge areas. (T)
District Has Primary Jurisdiction
E-4.2.1.3: Protect and preserve groundwater recharge areas.(P)
District Has Primary Jurisdiction
E-4.2.1.4: Improve water quality of listed impaired water bodies.(P and C)
District Advocates
E-4.2.2.2: Promote the protection and preservation of sensitive groundwater recharge areas. (T)
District Collaborates
E-4.2.2.4: Reduce pollutants in streams from urban runoff and minimize the effects on surface and ground water.
District Has Primary Jurisdiction
E-4.3.1.3: Support creek-side or water related recreation, as appropriate.