The Palo Alto Flood Basin was constructed in 1956 in order to prevent a repeat of the floods of 1955, when a high tide prevented the escape of heavy runoff from Matadero, Adobe, and Barron Creeks into the San Francisco Bay.
The trapped runoff waters overflowed upstream creek banks and caused severe flooding in Palo Alto.
In order to control the flow of water into the flood basin, a tidegate was placed at the confluence of Adobe Creek, Matadero Creek, and the San Francisco Bay, so that the flood basin could be maintained at approximately 2 feet below sea level, creating room to absorb floodwaters.
The tidegate consists of several weirs and one operator-controlled sluice gate that enables tidal flows into the basin in order to improve water quality and for mosquito control.
Three agencies oversee the tidegates: Santa Clara Valley Water District, City of Palo Alto, and Santa Clara County Vector Control.
Because the trash grate and weirs separate the mouth of the flood basin from the San Francisco Bay estuary, large fish cannot swim freely between the Bay and the basin, unless the sluice gate is open.
In addition, the tidegates are set to reduce tidal inflows into the basin, so that the basin is mostly freshwater.
After a rainstorm the tidegate is kept closed, however this is precisely when steelhead trout in-migrations should occur.
In 2002 a small opening was cut in the trash grate on the tidal gate to permit fish passage but local fisherman in the Flood Basin no longer report catching steelhead trout in recent years.

From November 16 to 20, 2002, approximately 100 striped bass (Morone saxatilis), 5 bat rays (Myliobatis californica) and 2 leopard sharks (Triakis semifasciata) were found dead in the Flood Control Basin in both Adobe and Matadero Creeks within one mile of the tidegate.
The fishkill was attributed to the first large rainstorm washing a large amount of leaf litter into the basin, leading to eutrophication and low dissolved oxygen.
This is supported by the fact that the dead fish were all large (requiring more oxygen) at 2 to 4 feet long and the mouths and gills of the bass were fully extended open.
The Palo Alto Flood Basin was constructed in 1956 in order to prevent a repeat of the floods of 1955, when a high tide prevented the escape of heavy runoff from Matadero, Adobe, and Barron Creeks into the San Francisco Bay. The trapped runoff waters overflowed upstream creek banks and caused severe flooding in Palo Alto. In order to control the flow of water into the flood basin, a tidegate was placed at the confluence of Adobe Creek, Matadero Creek, and the San Francisco Bay, so that the flood basin could be maintained at approximately 2 feet below sea level, creating room to absorb floodwaters. The tidegate consists of several weirs and one operator-controlled sluice gate that enables tidal flows into the basin in order to improve water quality and for mosquito control. Three agencies oversee the tidegates: Santa Clara Valley Water District, City of Palo Alto, and Santa Clara County Vector Control. Because the trash grate and weirs separate the mouth of the flood basin from the San Francisco Bay estuary, large fish cannot swim freely between the Bay and the basin, unless the sluice gate is open. In addition, the tidegates are set to reduce tidal inflows into the basin, so that the basin is mostly freshwater. After a rainstorm the tidegate is kept closed, however this is precisely when steelhead trout in-migrations should occur. In 2002 a small opening was cut in the trash grate on the tidal gate to permit fish passage but local fisherman in the Flood Basin no longer report catching steelhead trout in recent years.
From November 16 to 20, 2002, approximately 100 striped bass (Morone saxatilis), 5 bat rays (Myliobatis californica) and 2 leopard sharks (Triakis semifasciata) were found dead in the Flood Control Basin in both Adobe and Matadero Creeks within one mile of the tidegate. The fishkill was attributed to the first large rainstorm washing a large amount of leaf litter into the basin, leading to eutrophication and low dissolved oxygen. This is supported by the fact that the dead fish were all large (requiring more oxygen) at 2 to 4 feet long and the mouths and gills of the bass were fully extended open.
Adobe Creek (Santa Clara County)