Water trickling down the rocks

By Whitney Knueppel

In the El Niño winter of 1998, Cordilleras Creek topped its banks, causing severe erosion and property damage. The event prompted the City Council of Redwood City to meet with property owners and watershed residents and seek a solution to flooding. Many of the residents involved in the flood strategy process expressed an interest in keeping the creek in as natural a state as possible. In support of the residents’ position, the city funded a watershed program coordinator who will work with residents to identify the needs of Cordilleras Creek and plan for natural flood control, restoration, and ongoing creek care.

On April 8, 2002 a first step was taken in better understanding Cordilleras Creek. A hydrologist from a local consulting firm, a fisheries biologist from the California Department of Fish & Game, and two staff members from Redwood City Public Works Services embarked on a creek walk adventure. It was a revealing and enjoyable experience for all. The purpose of the walk was to identify fish passage barriers and to develop a visual log of conditions along the creek.

Cordilleras Creek and its tributaries drain approximately 2,380 acres. The creek trends east from the Pulgas Ridge Open Space to Steinberger Slough and eventually San Francisco Bay. The watershed covers portions of Redwood City, San Carlos, and part of unincorporated San Mateo County, and in many areas serves as the border between the two cities. The majority of Cordilleras Creek belongs to the property owners along its banks.

Our creek walk began at Highway 101 where Cordilleras Creek and Steinberger Slough come together. We moved up the creek toward Industrial Way then stopped at Redwood City High School, which owns about 500 linear feet of streambank upstream from Industrial Way. From this point on our trek was on foot or, in this case, in hip-waders. We crossed under the Caltrain culvert and under the El Camino Real culverts, both of which had plenty of water and were not perceived by the CDFG biologist to pose a barrier to fish passage. Just upstream of El Camino, land use adjacent to the creek becomes mainly residential and remains so until the Pulgas Ridge lands on the other side of Edgewood Road near Highway 280.

Cordilleras Creek flows through the backyards of hundreds of residents in Redwood City and San Carlos. It was evident that many of these residents are experiencing erosion, probably as a result of peak flows during large storm events. To combat property loss, many residents have placed hard structures such as concrete and gunite along the banks of the creek. While this may prevent loss for some, it could also contribute to bank erosion and instability for properties immediately downstream and on the opposite bank. Unfortunately, it is not a long-term solution, and it does not provide environmental benefits to fish and wildlife that live in the creek and use the riparian corridor. At some locations in this reach, where healthy riparian vegetation was observed, erosion and property loss were not.

We continued to walk upstream, following a pair of ducks to a culvert under Alameda de las Pulgas and another under Scenic Drive. At Scenic Drive the water levels were low enough in April that the concrete bottom of the bridge could clearly be seen. This does pose a barrier to fish passage. Also identified at this location was a dead mitten crab, which, because of its tendency to burrow into creek banks, is a threat to creek environments.

We continued walking upstream, still following the ducks, who were confused and a bit irritated that we persisted in trailing them no matter how far upstream they traveled. As we walked we saw many amazing reaches that provide healthy, functioning habitat for wildlife. We saw California roach in abundance, and we found several species of macroinvertebrates that provide food for fish. At several locations it was evident that residents had disposed of yard waste on the creek banks. This practice kills the underlying vegetation, causing erosion of the streambank.

Still in hot pursuit of the ducks, we worked our way along and soon encountered deer tracks. The creek is a corridor used by many kinds of wildlife. It provides foraging habitat and refuge from predators, as well as connectivity to outlying open spaces and other animal populations. Riparian vegetation, especially native plants, helps keep these corridors functioning and preserves their value to fish and wildlife. Vegetative cover helps keep streams shaded and water temperatures cool, another important aspect of a healthy creek.

A little farther upstream we saw a series of drop structures, and between the fourth and the fifth ones, we saw something that made us all very excited: the decomposed carcass of what may be an adult steelhead. This was a huge find. A great deal of research on historic distribution of steelhead in San Francisco Bay streams has been conducted over the last several years, but no data supporting either the presence or absence of steelhead in Cordilleras Creek has been located. Finding the presumed steelhead supports the theory that Cordilleras Creek could support a steelhead population. This makes ensuring the healthy functioning of Cordilleras Creek all the more imperative.

As we left the spot where we found the “steelhead,” things took a turn for the worse, from a fish’s point of view. Two five- to seven-foot weirs, coupled with a 200-yard culvert under Edgewood Road, prevent fish passage. The good news is that the area above Edgewood Road is mainly Mid-Peninsula Open Space District property, which means it will continue to provide refuge to wildlife (just not steelhead). However, steelhead habitat exists downstream of the weirs and with a little effort could easily be enhanced.

Overall observations by the hydrologist on our walk were positive. Despite hard structure and channelization, Cordilleras Creek continues to function as a natural waterway. There are many reaches where the banks slope naturally and provide both a floodway and a healthy riparian area. Additionally, much of Cordilleras Creek is supported by underlying bedrock, creating a more stable foundation for the creek.

Although there are challenges to stewarding the Cordilleras Creek and maintaining it in as natural state as possible, it is not an impossible goal.

Anyone interested in learning more about this project should contact Marilyn Harang, Superintendent of Wastewater, Redwood City Public Works Services, at 650 780-7436 or Barbara Patterson, Friends of Cordilleras Creek, 650 594-1164, babaloupat@yahoo.com.

Reprinted with permission from ‘Creeks Speak’, Fall 2002 a publication of The Watershed Project, Richmond, CA, 510 231-5703, www.aoinstitute.org.


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Last modified: October 14, 2004