Channelizing Aliso Creek
In 1999 the U.S Army Corps of Engineers conducted a Watershed Feasibility Study on the Aliso Creek Watershed and identified a number of water resource issues including erosion, habitat damage, and exposed sewer lines, coupled with high levels of bacteria from urban runoff. Since then Corps of Engineers and the county have been conducting a study on how to deal with these problems. The first version of a solution, known as the SUPER Project (for Stabilization, Utility Protection, and Environmental Restoration), has long been on hold for lack of funding but has recently resurfaced in the form of the Aliso Creek Ecosystem Restoration Feasibility Study.
Village Laguna opposed the SUPER Project because of its massive grading and channelization of the creek, which runs through a wilderness park. We participated in the scoping for this study in 2009, arguing that destroying the existing riparian vegetation, grading the canyon floor, and placing concrete and rock in the creek would be devastating to the wilderness park and inconsistent with Orange County’s General Plan.
Five years later, the study has received new funding and is expected to be complete by the end of next year. Unfortunately, the long-awaited alternatives turn out to be simply minor variations on the original. All of them have dams (now called not “drop structures” but “pools and riffles”) and armoring of the banks of the creek. The “ecological restoration” of the creek ecosystem will come only after the canyon has been graded and the creek has been equipped with concrete structures (16 now, rather than the original project’s 26) designed to keep it in its (new) place.
The study is expected to be distributed for public comment in March 2015, and Village Laguna will be reiterating its concerns about the approach.
Village Laguna’s contribution to the 2009 scoping session for the Aliso Creek Ecosystem Restoration Feasibility Study reads as follows:
The site of the study is Aliso and Wood Canyons Wilderness Park, a 4,000-acre natural park with steep hillsides, deep canyons, landscapes ranging from oak woodlands to grasslands and coastal sage scrub, and some thirty miles of trails. Dedicated to Orange County in 1979, it is designated in the County’s General Plan as a wilderness park, ‘a regional park in which the land retains its primeval character with minimal improvements and which is managed and protected to preserve natural processes.’ A deed restriction placed on it in 2001 limits it to county park uses in perpetuity.
The wilderness park is part of the Laguna Greenbelt, some 20,000 acres of protected open space surrounding the city of Laguna Beach. It is bordered on the north by residential and commercial development associated with the cities of Aliso Viejo, Laguna Niguel, and Laguna Woods. At the time the park was established (as mitigation for the development of Aliso Viejo), the upstream portions of Aliso Creek were beginning to be channelized to make way for development, and county planners hoped to preserve the rest of the creek in its natural state.
Planning for the park had begun even earlier. In December 1973 the University of California, Irvine, Extension held a conference entitled ‘The Aliso Creek: Potentials, Problems, and Public Policy’ coordinated by a former county planning commissioner and with an afternoon session led by a member of the county’s planning staff. Beginning in 1974, some 40 separate land parcels were assembled to create the park. The initial planning was funded by the California Coastal Conservancy, and later work was undertaken by the county’s Department of Harbors, Beaches, and Parks, often with funding from competitive state and federal grants. A proposed six-lane highway down the canyon as removed from the county’s Master Plan of Arterial Highways specifically to preserve Aliso Creek in its natural configuration. Over the years the canyon’s original riparian vegetation has gradually reestablished itself after more than a century of grazing. Although invasive species may be spotted in the riparian zone, the vast majority of plants are typical native riparian species, including cottonwoods, sycamores, willows, and mulefat. The county is pursuing funding for removal of the invasives, and we hope to see this work undertaken without waiting for any ultimate plan for the creek.
The Aliso Creek watershed inland of the park is now heavily developed, and recent years have seen a substantial increase in runoff as a result of this development that increased the flow of the creek, exacerbating seasonal flooding, and poured urban pollutants into it. Much of this development was made dependent on a commitment not to increase runoff into the creek, but the facilities for fulfilling this commitment have not been established.
At the same time as being the heart of the wilderness park, Aliso Canyon has become the conduit for treated wastewater from the treatment plants of the surrounding communities to the ocean outfall at Aliso Beach. The original idea, when the Aliso Wastewater Management Agency was founded in 1974, was that the inland cities would recycle their wastewater. The outfall constructed along the creek was expected to be used only in winter, when the supply of reclaimed water would exceed the demand for it. Although recycling is under way in the various inland water districts, the demand for outfall capacity has increased over the years. The existence of sewer pipes in the ground along the banks of the creek and the desire to install more of them have created a perceived need to lock the creek in place so that these pipes will not be threatened by erosion.
The project that Orange County calls the SUPER Project—whose acronym stands for Stabilization + Utility Protection + Environmental Restoration—is primarily an attempt to prevent the creek from encroaching on these pipes. It involves (1) the construction of a buried riprap wall 3 miles long beside the maintenance road east of the creek, (2) twenty-four 2-foot grouted-rock drop structures sunk into bedrock, each with a 30-foot-long basin below it that will be protected on both banks with stone, (3) two 6-foot drop structures with 150 feet of concrete revetment downstream of them along both banks, and (4) realignment significant filling of the channel. According to the County’s Aliso Creek Concept Report (February 2006), ‘The actual channel will not be intact in much of the project reach’ (p. 27). Grading is expected to be so extensive—involving some 70 acres of the canyon floor and moving 1 million cubic yards of earth—that there will be little opportunity to preserve desirable stands of existing vegetation (p. 28).
The objectives of the Aliso Creek Mainstem Ecosystem Restoration study bear a close resemblance to those of the SUPER Project, though the study makes no mention of protecting utilities and lacks the project’s water-quality component. As does that project, it involves grade controls and the raising of the floodplain, and one Corps supporter at a recent meeting declared that restoring a creek in a developed area sometimes requires concrete. Further, the techniques for restoration of vegetation described by David Derrick of your Vicksburg office all seem to involve the import of tons of rock. All this and the fact that the SUPER Project closely follows the recommendations of an earlier Corps of Engineers study for Aliso Creek persuade us that our concerns about damage to the creek and the wilderness park remain relevant in the new context.
Destroying the existing riparian vegetation, grading the canyon floor, and placing concrete and rock in the creek would be devastating to the wilderness park and are inconsistent with the County’s General Plan.
The County’s 2008 draft resource management plan for the park, produced with broad public input, is described as a blueprint for ‘protecting and preserving the native habitat in the park for the benefit of its natural resources and providing outdoor education and low-impact recreation consistent with resource protection goals.’ It proposes improving the quality of the water in the creek through such methods as manufactured wetlands and portable filters. It also calls for assessing proposed projects for their potential impacts to park resources.
The technical review of the concept plan by an outside consulting firm (Aliso Creek Concept Plan Report, Technical Review, prepared by Geosyntec in January 2007) stresses the importance of addressing the causes of creek instability and water-quality degradation and the potential for limited mitigation measures to have unintended consequences (p. 16). It indicates that the two-year storm event for which the channel is to be designed may or may not be appropriate (p. 10) and points to ‘indications that past efforts at peak-flow ‘shaving’ for a series of storm events (two-year and up) have not successfully protected the creek and have actually accelerated stream erosion’ (p. 16). The review recommends consideration of ‘alternatives that may result in improvements in design, cost savings, and/or improved habitat,’ among them the use of (1) biotechnical streambank stabilization methods, (2) methods that could lengthen flowpaths and reduce the required amount of grade control, (3) tiered levels of protection, and (4) creek enhancement measures promoting a return closer to natural hydrologic wetting patterns and biodiversity (p. 11). It also recommends the development of upstream detention and retention facilities to ‘reduce pollutant loadings throughout the creek, mitigate dry weather flows, and reduce required capacity of treatment downstream’ (p. ES-3). ‘Without an integrated, strategic approach,’ it concludes, ‘SUPER Project benefits could be limited in longevity and multi-benefits, as pollutant and hydrologic loading could stress, and potentially reimpact, the restored creek segments’ (p. ES-3).
The Concept Report itself (p. 40) identifies five sites—two in the park and three on public land owned by cities—on which detention, infiltration, or wet basins could be constructed. An additional site that has recently attracted attention is the huge parking lot of the federal building on Alicia Parkway locally known as the Ziggurat, which is now for sale.
The Aliso Creek Stabilization Project Review prepared by Phillip Williams and Associates for the City of Laguna Beach (May 29, 2009) suggests that, contrary to the assessment of the earlier studies, the relevant section of the creek (from Alicia Parkway to the sewage treatment plant) may be close to or at equilibrium and starting to form a new floodplain. Accordingly, it suggests that the channel could be stabilized by introducing as few as three 2-foot and two 6-foot grade control structures or, alternatively, by stabilizing the base of the ACWHEP structure and allowing another 6 feet of incision downstream. The latter alternative would allow the self-formation of an equilibrium system that would be ‘more likely to be resilient to large flood events than a system that is kept out of equilibrium using hardscape, as well as likely to function [more naturally] and appear more natural’ (p. 23). The PWA review advises the City to have fairly modest expectations about using upstream stormwater control to reduce erosion downstream but to take advantage of opportunities to ensure that future development upstream does not make matters worse and to improve the situation incrementally through low-impact development and stormwater detention. In further contrast to the Concept Report, in which the effects on sand supply to the beach are considered indeterminate, the PWA review considers the sand discharged from the creek ‘very important to the system’ of maintenance of our beaches and not something that should be ‘locked in place’ to stabilize the creek (p. 25).
The proposed new wastewater management regulations (Revised Tentative Order R9-2009-0002)—the MS4 permit—under review by the San Diego Regional Water Quality Control Board includes stricter regulations of discharges into the creek that can perhaps be expected to reduce the excess flow that is so important a part of the problem. It would prohibit dry-weather discharges into the creek, thus helping to return it to something more like the intermittent stream that historically it was, and require controls on stormwater discharges through the careful planning of new development and retrofitting of existing development with detention basins.
The current water shortage and new state laws requiring water efficiency in landscaping in response to that shortage are likely to serve as additional incentives for capturing and reusing much of the water that now ends up in the creek.
The various reports of the creek stabilization proposals agree that past efforts to rein in the creek with concrete and rock have been a failure and have actually contributed to its erosion. The drop structure known as the Aliso Creek Wildlife Habitat Enhancement Project (ACWHEP) is an eyesore in addition to a testament to this failure and ought to be demolished. Elsewhere in the country, we understand, the results of such efforts are being dismantled in favor of natural solutions. We hope that the feasibility study will take our concerns about this approach into account and that a noninvasive solution to Aliso Creek’s problems will emerge from it.