North Alameda and Southwest Alameda Watersheds
The North Alameda and Southwest Alameda watersheds drain Alameda Island, which occupies most of the city of Alameda and is located across the Oakland Estuary from the city of Oakland. The 3.4-square-mile North Alameda Watershed covers the majority of the island, including the urbanized area in the north and the former Naval Air Station, now known as Alameda Point. This former Naval Station is now a mixed-use community of wetlands, grasslands, and commercial areas. The Southwest Alameda Watershed covers 1.03 square miles and includes the Southshore area, which is separated from the main section of the island by Alameda Lagoon. Both Alameda Point and Southshore are filled baylands and are relatively flat. Therefore, surface water is transported not by creeks but by a complex system of storm drains that empties into the estuary, San Leandro Bay, and San Francisco Bay–the water bodies that surround the island and the lagoons.
Flora and FaunaSeveral plant habitats can be found on Alameda Island: grassland, seasonal wetlands, and northern coastal salt marsh. Grassland communities support native grasses and wildflowers, though the majority are now nonnative grasses such as tall fescue, Bermuda grass, pampas grass, and cordgrass. Seasonal wetlands provide habitat for native plant species such as Monterey centaury, common nut sedge, and arroyo willow. Reptiles and amphibians such as the Western fence lizard have been observed in Alameda Point in addition to raptors like the northern harrier and white-tailed kite. Mammals in the watershed include the Virginia opossum, gray and red fox, California vole, raccoons, and skunks. Shorebirds, both migratory and residential, nest on the island as well; these include the endangered California least tern. A population of green sturgeon, which is a federally threatened species and California species of special concern, has been found in the waters designated as essential fish habitat near the island.
Geology and HydrologyAlameda Island is a sand dune that formed during the last ice age over 10,000 years ago. Its porous soils allow rainwater to soak in, hence there are no natural creeks on the island. It was originally a low lying peninsula whose sand, known as the Merritt Sand, was deposited during or shortly after the last ice age when sea levels were low and San Francisco Bay was a wide river valley. When the sea level rose, the tops of the dunes remained. Areas of the peninsula that were on higher ground once harbored one of the largest coastal oak forests in the world. (Alameda is Spanish for grove of poplar trees or tree-lined avenue.) Alameda is the largest island in San Francisco Bay. Its area doubled in the 1850s when artificial bay fill from mining debris and dredging for shipping channels was used to fill many of the marshlands and tidal flats of the bay. On Alameda Island, bay fill was composed mainly of Merritt sand, bay mud, Temescal formation debris, broken rock, and miscellaneous refuse.The average annual precipitation in Alameda is 20.81 inches. Groundwater in the area occurs at shallow depths and at the surface, taking on a brackish quality as it mixes with the saline waters from San Francisco Bay. Central Avenue stretches from one end of the island to the other and serves as a loose point of reference for its spine. The avenue also divides North Alameda Watershed from Southwest Alameda Watershed. Municipal storm drains carry surface runoff into a system of underground culverts that empty into the surrounding bodies of water.
Major IssuesStorm water conveyance, flooding, global sea level rise, littering, nonnative plant species, shoreline erosion, and trash hot spots due to the tides are the main environmental challenges. The city is mandated to conduct annual cleanups at four trash hot spots subject to tidal accumulation.
Major Creeks & Waterbodies
North Alameda WatershedA system of storm drains and underground culverts drains the northern side of Alameda Island into the Oakland Inner Harbor or estuary.
Oakland EstuaryThe Oakland Estuary is a strait that separates the cities of Oakland and Alameda, its eastern end connecting to San Leandro Bay and its western end to San Francisco Bay. U.S. Coast Survey maps from the 1850s label this arm of the bay San Antonio Creek. Since that time, dredging and manufacturing industries have caused much sedimentation and contamination.
Runway WetlandRunway Wetland was originally tideland characterized by open water during high tide and mud flats during low tide. The land was filled to make the runways, roads, and sea wall for the Naval Air Station Alameda. San Francisco Bay water that enters through the seawall, as well as precipitation and surface runoff, has created a shallow marsh with tidal marsh vegetation. Roughly 16.5 acres, the wetland is dominated by pickleweed and saltgrass as well as nonnative plant species such as iceplant. This artificial wetland is located at the southern edge of Alameda Point and is separated from San Francisco Bay by the seawall.
San Francisco BaySan Francisco Bay is a shallow and productive bay and estuary. Since the mid-19th century, up to one-third of the original bay has been built upon or filled in using dredging material from the bay and excess soil from development projects. Only about 20 percent of the original tidal marshes that ringed the bay remain today.
West WetlandWest Wetland is an artificial wetland on Alameda Point that includes 32.4 acres of shallow ponds and vegetated salt marsh. The dominant plant species are pickleweed and saltgrass. The higher areas are susceptible to invasive plant species such as iceplant, cranesbill, ox-tongue, and coyote brush.
Southwest Alameda WatershedA small network of underground culverts and storm drains empties into San Francisco Bay.
San Leandro BaySan Leandro Bay is an arm of San Francisco Bay, located along the east side of the Oakland International Airport and Bay Farm Island. Once a rich habitat for wildlife, most its original marshland and habitat have been filled or dredged, with the exception of Doolittle Pond and Arrowhead Marsh (City of Oakland).
North Alameda Watershed TrailsAlameda Point is the former Alameda Naval Air Station on the western end of Alameda Island. It is currently in the process of being transferred from the U.S. Navy to the City of Alameda for future development that would include a strong commercial base with open space, recreational, residential, and retail uses. On June 4, 2013, the city took title to about 1,400 acres of land and water from the Navy. Over 700 acres of parks and open space will be preserved at Alameda Point, and a Bay Trail extension is planned around the shoreline to connect new parks.
Southwest Alameda Watershed Trails
Pedestrian/Bike Bridge and Water WalkA pedestrian/bike bridge connects Alameda with adjacent Bay Farm Island. It is located next to the Aeolian Yacht Club at 980 Fernside Boulevard. Visitors can enjoy this casual walk over the bridge and take in views of San Francisco Bay.
North Alameda Watershed Parks and RecreationFor a list of municipal parks on Alameda Island, please see the Parks & Facilities section of the City of Alameda website.
Southwest Alameda Watershed Parks and RecreationFor a list of municipal parks on Alameda Island, please see the Parks & Facilities section of the City of Alameda website.
Ongoing restoration projects in these watersheds serve to preserve and enhance the environment through invasive plant removal, shoreline recreational opportunities, and erosion control. The City of Alameda, in conjunction with the California Coastal Conservancy, is removing cordgrass along the estuary, San Leandro Bay, and Crown Memorial Regional Shoreline. The Crown Memorial State Beach Sand Project has brought in 82,600 cubic yards of sand for erosion control. Information about other restoration projects can be found on the City of Alameda website and on the California Department of Fish and Wildlife website.
There are several organizations involved in restoration efforts, litter removal, and educational programs. The East Bay Regional Park District, in partnership with the City of Alameda Parks and Recreation, the YMCA, and the Boys and Girls Club, will implement the Fishing Outreach Program in 2014 for youth and adults. This program will focus on shoreline and bay fishing and complement EBRPD’s ongoing inland freshwater fishing programs.