Wetlands and Riparian Corridors

PUBLIC AND SCIENTIFIC views of wetlands have changed greatly over time. Once considered to be of little or no value, wetlands were viewed not only as breeding grounds for diseases like malaria, but as barriers to urban development and agricultural production.

Although our understanding of the functions and values of wetlands has increased dramatically, and government agencies have established programs in attempts to protect them, it is estimated that 95% of the Bay's historical coastal wetland acreage has been lost. Additionally, the effects of encroaching urbanization have significantly degraded even those wetlands that remain. These new developments also required protection from flood hazards. As a result, the vast network of natural rivers and streams that once existed in the Bay watershed has been largely replaced by more than 5,000 miles of concrete channels, culverts and underground pipes.

Similar changes in the public and scientific view of rivers and streams have greatly impacted the health of riparian habitats in the region. Over the years, people have employed channelization as the only effective means with which to protect urban dwellings from flood hazards. Accordingly, a vast network of natural riverine and palustrine habitats have been replaced with more than 5,000 miles of concrete underground pipes and channels.

Malibu Lagoon and Creek

A 20-acre brackish lagoon and salt marsh lies at the mouth of the 110 square mile Malibu Creek watershed. The creek itself is the largest unchannelized stream in the Santa Monica Bay watershed. The lagoon is a remnant of what was once a much larger system, most having been filled for commercial and residential development in the City of Malibu. Together, the remaining creek and lagoon complex support many terrestrial and aquatic species, some of which are threatened or endangered. These include the Tidewater goby and Steelhead trout. The area is also home to several threatened and endangered birds, including the Brown pelican, California least tern and the Willow flycatcher, and represents a vital stopover for migratory birds along the Pacific Flyway.

Issues of concern in the lagoon and creek include excessive freshwater inputs from urban runoff and imported water; high nutrient, pathogen, and bacteria levels; sedimentation; contaminated runoff; loss of habitat; and invasive species.

Excessive freshwater inputs from both the Tapia wastewater treatment plant and urban runoff, along with the occasional mechanical breaching of the lagoon/ocean barrier beach, disrupt the natural hydrologic cycle and subject the lagoon to sudden, drastic changes in salinity. Such sudden changes place enormous stress on the biotic community. High nutrient concentrations in the creek can create eutrophic conditions in the lagoon. Elevated levels of bacteria and pathogens from a variety of potential sources (including malfunctioning septic systems, animal waste, storm drains and treatment plant discharges) adversely affect human health, increasing the risk of illness for swimmers and surfers.

Invasive plants and animals such as the Giant reed (Arundo donax), Castor bean, Wild tree tobacco, Crayfish, Bullfrogs, Mosquito fish and Largemouth bass decrease the biological diversity of native ecosystems by out-competing or displacing native species. They also reduce habitat and water quality/availability for the native species.

Blocked access to spawning and rearing habitat is a major obstacle to the recovery of steelhead trout in Malibu Creek as well as the entire Santa Monica Bay watershed. It has been estimated that more than 80% of the spawning habitat, and 60% of the rearing habitat has been made inaccessible to steelhead in Malibu Creek as a result of passage barriers such as Rindge Dam, culverts, and Arizona crossings.

Many studies have been completed and several restoration projects have been implemented to address impairments in the Malibu Creek watershed. The Tidewater goby, completely extirpated from the lagoon by 1970, was successfully reintroduced in 1991 and continues to thrive. In 1996, over 2,000 cubic yards of old fill material was removed from the lagoon and additional aquatic mud flat and high storm flow refugia habitats were created for birds, fish, and other aquatic species. In the upper watershed, a 200-foot reach of Las Virgenes Creek was restored by recontouring the banks, removing non-native vegetation, and replanting with native species. The Mountains Restoration Trust has recently initiated a six-year program to remove Arundo donax from a five-mile stretch of the creek. To help reduce excess flows, the Tapia treatment plant is now prohibited from discharging its effluent into Malibu Creek from April 15th through November 15th. The Army Corps of Engineers is currently evaluating the feasibility of removing Rindge Dam to restore access to an additional 8 miles of steelhead habitat. Heal the Bay's Stream Team volunteers collect baseline data to determine the current conditions of the Malibu Creek Watershed. To find out more about what's being done to restore the lagoon and creek, download "Making Progress: Restoration of the Malibu Creek and Watershed"

Ballona Wetlands & Creek

Located adjacent to Marina Del Rey, the Ballona Wetlands complex (including Ballona Creek & Lagoon, Del Rey Lagoon, as well as salt marsh, mudflat, dune and bluff habitats) has been reduced to less than ten percent of its historic dimensions. Oil and gas exploration, urban sprawl, the development of the marina, and the channelization of Ballona Creek have all reduced what was once a 2,200-acre coastal estuary to less than 200 degraded acres today. Poor tidal exchange, polluted runoff, and invasive plants and animals also impact the wetlands.

Despite its degraded condition, the wetlands still play host to numerous terrestrial and aquatic species such as the Long-jawed mudsucker, Shadow goby, California killifish, the federally-listed endangered California least tern and the state-listed endangered Belding's savannah sparrow. The wetlands, like Malibu Lagoon, also serve as a stopover for migrating birds along the Pacific Flyway.

Current restoration plans, although incomplete and controversial, would increase wetland and upland habitat to approximately 350 acres, including a recently completed 25-acre freshwater marsh. The freshwater marsh will increase wildlife habitat, treat runoff from nearby development, and supply fresh water to the salt marsh in order to create appropriate brackish conditions. Additional plans center on restoring 200 acres of saltwater marsh, including a Least tern nesting island, a 25-acre riparian corridor, and 100-acres of dune, coastal sage scrub, and other native upland habitat. Eventually, tidal connections will be reestablished, fill will be removed, and native vegetation will be reintroduced.

Ballona Lagoon was the site of a major restorationin 1997. Activities included: dredging at the southern end of the lagoon to create a deep water pool, removal of inactive oil pipelines and an abandoned concrete structure from the middle of the lagoon, stabilizing the lagoon banks with native vegetation, and constructing a visitor's overlook.

Ballona Creek is the largest (130 square miles) watershed in the Santa Monica Bay and it contributes a major portion of the total pollutant load entering the Bay. The creek drains the west central area of Los Angeles, and the southeastern portion of the Santa Monica Mountains. Most of the creek was channelized in the 1930s for flood control, and consequently, little riparian habitat remains. To address impairments to waterbodies in the Ballona Creek watershed, the Bay Restoration Commission, in partnership with the Los Angeles County Department of Public Works Watershed Management Division and the Ballona Creek Renaissance, is leading the effort to develop a comprehensive Ballona Creek watershed management plan.

Topanga Lagoon & Creek

Covering approximately 18 square miles, 75% of which is undeveloped, Topanga Creek is Santa Monica Bay's third largest watershed. A variety of plants and animals, including federally-endangered Steelhead Trout and Tidewater Goby, as well as species of special concern such as the Western Pond Turtle, the California Newt, the California Tree Frog and the Two Striped Garter Snake are native to the watershed. Although it is one of the least altered and most biologically diverse drainages in Santa Monica Bay, its resources are suffering from impacts of human activities. Of special concern are the degraded lagoon and several stretches of stream bank in the lower watershed.

Historically, Topanga Lagoon covered more than 30 acres. In 1934, Caltrans realigned Pacific Coast Highway (PCH) inland, placing over 800,000 cubic feet of fill material directly into the lagoon, reducing its surface area by 94% to its present day size of 2 acres. Water quality in the lagoon is impaired due to elevated bacteria (total coliform, fecal coliform, E.coli) levels. Although yet to be identified, there are several potential sources for high bacteria counts including; poorly maintained septic systems (all 4,500 homes and commercial buildings in the watershed are on septics), greywater systems, and corralled animals. The lagoon is further threatened by the presence of invasive exotic vegetation including; Arundo donax, Castor bean, German ivy, Morning glory, and Pampas grass which have all become well established, crowding out native Cattails and Willows.

In the upper Topanga Creek, the issue of greatest concern is habitat degradation due to road maintenance practices along Topanga Canyon Road. Over the years, Caltrans has replaced extensive sections of stream bank with grouted riprap, concrete, and boulders as emergency flood repairs following storm damage to Topanga Canyon Road. Due to the emergency nature of these repairs, most are poorly engineered and require extensive maintenance. Many of these repairs have filled and constrained the stream channel, inducing landslides, increasing sedimentation, and impeding fish migration, including that of the endangered Steelhead trout. The upper Topanga Creek is also listed on the State 303d list of impaired waterbodies.

In support of restoration of the creek and lagoon, the SMBRP and other agencies have conducted a comprehensive Topanga Creek Watershed and Lagoon Restoration Feasibility Study to identify ways restore the watershed's resources. The report's recommendations for lagoon and creek restoration will serve as a guide for all stakeholders, especially Caltrans and the California Department of Parks and Recreation, which recently purchased 1,659 acres in lower Topanga Canyon including the current and historic lagoon acreage, to develop a comprehensive plan for restoration. Additionally, the Topanga Watershed Committee has been implementing actions identified in the Topanga Creek Watershed Management Plan. Activities include water quality monitoring, creek clean-ups, crayfish control, and various community workshops dealing with watershed issues.

Zuma Wetlands

Zuma Wetlands is a small, 6-acre, freshwater marsh and creek situated just north of Point Dume. The wetlands have historically served as a wildlife corridor and nesting site for a variety of birds and small mammals. By the early 1990s periodic dumping of surplus construction and road building material had heavily impacted the wetlands and surrounding uplands. The existing wetlands had been greatly reduced and, in many areas, native species had been completely replaced by exotic ornamental trees, annual grasses, fennel, mustards, and thistles. High visitation at Zuma Beach and the use of the riparian area as a "camp" by homeless inhabitants also impacted the site.

Despite the long-term habitat degradation, studies indicated that the site had high potential for successful restoration. In the fall of 1993, federal, state, and nonprofit conservation agencies began planning efforts for a restoration of the remnant freshwater marsh, riparian woodland, saltgrass terrace, and locally rare foredunes at the site. A final restoration plan was completed in April 1997 and, in 1998, a partnership consisting of the Santa Monica Bay Restoration Foundation, the National Park Service, and the Los Angeles County Department of Beaches and Harbors began the wetland restoration. Over the next two years, excavation of construction fill, recontouring of upland habitats, removal of exotic plant species, in-planting of more than 5000 native plants, and the re-creation of an additional 2 Ѕ acres of freshwater wetland/dune/riparian habitat was accomplished. The resulting restored wetland has an unusually diverse and highly valuable habitat for wildlife. As an example, more than 110 bird species (PDF) were recorded over a one-year monitoring period. The project continues to be monitored for exotic species control and habitat protection.