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Drainage through the 2.6-square-mile Elmhurst Creek Watershed begins at the ridge near Bishop O’Dowd High School in south Oakland and flows entirely through a network of underground storm drains until it reaches San Leandro Street near Hegenberger Road. Three open channels begin in this area before merging into Elmhurst Creek and entering San Leandro Bay near San Leandro Creek and Arrowhead Marsh.
Flora and Fauna
The Elmhurst Creek Watershed drains residential and industrial areas of south Oakland entirely through engineered channels and underground culverts. As a result, the watershed supports few plants and animals until it approaches the bay. The entire shoreline of San Leandro Bay was once thick with tidal marsh giving way inland to seasonal wetlands. The marsh was filled and developed for industrial uses, but in recent years much of the marsh and seasonal wetlands have been restored. Parking lots have been converted to seasonal wetlands with salt grass and pickleweed. In tidal areas, gum plant, salt grass, pickleweed, and cord grass are the dominant plant species, which typically grow in that order from higher marsh plain to lower. Pickleweed along the interior marsh is prime habitat for the state and federally endangered salt marsh harvest mouse. Cord grass is prevalent along tidal sloughs and channels, and salt grass is returning along the inland rim of the marsh. Native cord grass and the nearby small sandy beaches that dot the edge of San Leandro Bay create prime habitat for the state and federally endangered clapper rail and the endangered California least tern, respectively.
Geology and Hydrology
Drainage along the ridge near Bishop O’Dowd High School flows through Jurassic era volcanic rock and then across a large sandy plain that was formed by several creeks in the late Holocene epoch. Approaching the shoreline, Elmhurst Creek flows through a mile of artificial fill of unknown origin before reaching the bay. In the past, it was not uncommon to fill shallow water basins, tidal flats, and tidal marshes along the San Francisco Bay shoreline for expansion projects.Click here for an explanation of how tidal marshes originally formed in San Francisco Bay with rising and falling sea levels during the Holocene epoch.
San Leandro Bay is on California’s list of Toxic Hot Spots due to excessive levels of DDT, lead, mercury, pesticides, PCBs, PACs, selenium, and zinc in its sediment. In sediment tests, the highest concentrations of contamination were found near creek channels, indicating that the sources are from point and nonpoint inputs. The one exception was mercury, which had higher concentrations in open water areas compared to tributaries. A Watershed Survey Report prepared for the Regional Water Quality Control Board found that concentrations of chemical contaminants near the mouth of Elmhurst Creek exceeded the board’s guideline values, that toxicity levels were detrimental to invertebrate reproduction, and that sediment was highly toxic to amphipods (marine crustaceans).
Major Creeks & Waterbodies
Upper Elmhurst Creek, which drains the canyons behind Hellman Recreation Center in Oakland, has been rerouted into San Leandro Creek so is no longer part of the Elmhurst Creek Watershed. Elmhurst Creek once ran its natural course through south Oakland along the edge of San Leandro Creek’s alluvial fan to San Leandro Bay. These alluvial deposits remain the defining edge of the Elmhurst Creek Watershed. Today, Elmhurst Creek flows through an engineered channel that begins west of San Leandro Street, crosses under Hegenberger Road, and runs along the south side of the Oakland Coliseum complex to San Leandro Bay near Arrowhead Marsh.
San Leandro Creek and Elmhurst Creek enter San Leandro Bay through engineered channels at Arrowhead Marsh near the Oakland International Airport. Arrowhead Marsh is a young tidal marsh that was likely created during the construction of the Lake Chabot dam when a severe storm sent 21,000 cubic yards of the dam’s clay core downstream to the mouth of San Leandro Creek. Since the creation of the Martin Luther King Jr. Regional Shoreline, surrounding marshlands have been restored, expanding this important habitat for shoreline birds and migratory waterfowl.
San Leandro Bay
San Leandro Bay is a small inlet within San Francisco Bay bounded by the Oakland shoreline, Bay Farm Island to the south and Alameda Island to the north. The Martin Luther King Jr. Regional Shoreline covers a large portion of the San Leandro Bay shoreline and is also the location of two tidal marsh and seasonal wetland restoration sites. San Leandro Bay is actually the catchment for several different watersheds. For more information, click on the name of any of the following creeks that flow to this embayment: Sausal Creek, Peralta Creek via East Creek Slough, Lion Creek via Damon Slough, Elmhurst Creek, and San Leandro Creek.
Several trails and parks are accessible to the public for walking, biking, and recreation near the shoreline.
The San Francisco Bay Trail (Bay Trail), when complete, will circumnavigate the entire bay. Within the Marin Luther King Jr. Regional Shoreline in Oakland, the Damon Marsh Trail, Garretson Point Trail near the mouth of Elmhurst Creek, and the Arrowhead Marsh Trail follow the shoreline of San Leandro Bay and are all part of the Bay Trail network.
Tidewater Boating Center
At the Tidewater Boating Center and the Doolittle Staging area at San Leandro Bay, boaters will find launch sites for the San Francisco Bay Water Trail, an innovative “trail” system designed for people with a variety of boating skills. The launch and landing sites, or “trailheads,” provide human-powered boats and beachable sail craft access to San Francisco Bay for multiple-day and single-day trips. Providing access to isolated San Leandro Bay, these two sites in particular are ideal for less experienced kayakers.
Parks and Recreation
The 741-acre Martin Luther King Jr. Regional Shoreline includes most the shoreline of San Leandro Bay. The park is leased from the Port of Oakland by the East Bay Regional Parks District to preserve what remains of a former extensive tidal marsh and to provide public access to the shoreline. The park contains the Tidewater Boating Center and Arrowhead Marsh, which is believed to have been created by sediment carried downstream when Lake Chabot’s dam burst during construction. The marsh is a stopover on the Pacific Flyway and part of the Western Hemisphere Shorebird Reserve Network, an organization dedicated to protecting shorebird habitat at sites across 13 countries covering 31 million acres.
The Martin Luther King Jr. Regional Shoreline includes the last remaining tidal marshes in San Leandro Bay; the others have been filled in for development. In 1998, at the “handle” of Arrowhead Marsh, fill was removed, artificial levees were breached, and tidal channels were constructed to restore tidal action. Plant and animal colonization began shortly thereafter and continues today. Between Elmhurst Creek and Damon Slough, the East Bay Regional Parks District and Save the Bay maintain a native plant nursery for their restoration projects that focus on removing nonnative plants and replacing them with natives.
Information about volunteer and educational opportunities can be found by visiting these sites.