Alviso Slough is the last reach of the Guadalupe River before it enters San Francisco Bay. The community of Alviso is located on the east bank of the Slough. The Alviso Marina County Park, Don Edwards San Francisco Bay National Wildlife Refuge, and Cargill salt ponds occupy most of the area in Alviso that is outside the Urban Service Area. Coyote Creek, which drains a very large watershed, enters the Bay to the north of Alviso. Alviso Slough was historically used for commerce and recreational boating; however, the reach of downstream of the Gold Street Bridge has experienced a gradual decline in channel width and increasing encroachment from vegetation over many years. These conditions have come about in the past century, primarily because of human activities, such as the manipulation of the South Bay marshlands and drainage channels for both salt-making (evaporator ponds) and agricultural purposes.
Realignment of channel meanders for more efficient flow conveyance, groundwater over-pumping (resulting in subsidence of low-lying areas), and urban development have also played a role in redefining the natural course and flow conveyance of both the Guadalupe River and Alviso Slough. These anthropogenic influences, combined with natural processes attempting to achieve a level of equilibrium, have resulted in a reduced channel width and depth, precluding use of the slough for navigation and recreational access. For many years, members of the community of Alviso have requested restored access to the slough for its historic use.
The Santa Clara Valley Water District (District) Board approved a motion on January 20, 2004 directing staff to “prepare a project that includes the following: Phase 1, removal of 7 acres of vegetation and root mass to a depth of four feet on both banks of the Alviso Slough from the Gold Street Bridge to the County Marina; and then in the following year a long term project related to bringing in salt water.”
Project objectives aid in identifying a range of suitable and feasible project alternatives. Following the January 2004 Board directive, District staff entered into a collaborative agreement with members of the Alviso community (Alviso and Lower Guadalupe Collaborative) in an effort to develop a project that would meet the interests of the community. Through the collaborative effort, the following project objectives were established:
- Restore Alviso Slough’s channel width and habitat to prior to 1983 conditions;
- Improve the community’s ability to pursue navigation, public access, and aesthetics to allow for the expansion of boating and other recreational and/or tourism opportunities;
- Maintain one-percent flood protection in Alviso Slough;
- Reduce mosquito nuisance; and
- Promote the integration of the Alviso Slough Restoration project with the South Bay Salt Pond (SBSP) Restoration Project (including the SBSP Phase 1 Action at Pond A8) to re-establish the saltwater connection to the Lower Guadalupe River.
Deputy Operating Officer
408-265-2607, ext. 2379
Deputy Operating Officer
(408) 265-2607, ext. 3126
Senior Project Manager
(408) 265-2607, ext. 3117