Lower Colgan Creek Restoration Project
The Lower Colgan Creek restoration projects aims to restore a 1.3 mile-long portion of creek in southwest Santa Rosa. The Project will increase channel sinuosity (meander pattern of the creek), re-grade the cross section to a more natural geometry, enlarge the channel, and install a series of pools and riffles. In addition, the Project will remove invasive plants and install genetically appropriate, native vegetation across the riparian corridor. The current earthen flood control channel, sized to carry the 25-year flood, will be expanded to provide 100-year flood protection to increase groundwater infiltration and protect area homes and businesses. A bicycle and pedestrian path will extend on the west side of the creek providing a safe Class 1 pathway in proximity to regional transportation facilities.
Phase I of the project was completed in 2014 and transformed the flood control channel into a 2,000 foot-long restored creek adjacent to Elsie Allen High School. The completed channel restoration included constructed riffles, large woody debris habitat structures, boulder step pools, enlarged floodplains, and extensive native riparian plantings.
Phase II of the project was recently completed and involved a large-scale stream restoration and flood resiliency project nearly 1,900 linear feet. This Phase included numerous large woody debris habitat structure, constructed riffles, enlarged floodplains, a paved multi-use pathway, and extensive native riparian plantings.
Phase III is planned next fill the critical gap between Phases I & II. Similar enhancements and treatments are planned for this Phase, with the addition of a bicycle and pedestrian bridge over the creek. Completion of Phase III will ensure contiguous habitat along the entire project area and increased flood protection for southwest Santa Rosa.
The project will greatly enhance the natural functioning of Lower Colgan Creek and is designed to provide the following community and environmental benefits:
- Increase the riparian canopy in both width and cover over the restoration reach. The widened channel will increase the area available for aquatic and terrestrial species living within or migrating along the creek.
- Increase stream length by ~250 feet in Phase 2 by re-creating a meandering channel.
- Increase habitat diversity with log habitat structures to support pool development; boulder clusters to create natural riffles; and in-channel islands to support a variety of organisms and their life stages. In addition, the Project will add floodplains dominated by sedges (Carex sp.) and rushes (Juncus sp.), with a dominant tree canopy of oaks (Quercus sp.) and willow (Salix sp.).
- Remove invasive species and install genetically appropriate native species throughout the Project area. The site is dominated by Himalayan blackberry (Rubus armeniacus), poison hemlock (Conium maculatum) and non-native grasses like Harding grass (Phalaris aquatica), rip-gut brome (Bromus diandrus) and wild oat (Avena fatua).
- Increase flood capacity of the channel from 25-year to 100-year flood capacity, by increasing the channel width and reconnecting the creek to a portion of its historical floodplain.
- Increase ground water infiltration by slowing the flow within the channel. The Project will increase the thalweg length from 1,950 to 2,200 feet by introducing meander into the existing flood control channel.
- Improve water quality by reducing sediment from failing banks, increasing canopy cover over the channel and providing a vegetated floodplain that increases the surface area for plants to cleanse pollutants and excess nutrients from the storm runoff.
- Provide educational opportunities to the schools in the watershed. Phase 1 of the Lower Colgan Creek Restoration Project developed curriculum for elementary and high school students. This curriculum includes support for participating teachers to conduct water quality monitoring, native plant identification and propagation, bioassessment of benthic macroinvertebrates and participation in creek restoration. Phases 2 and 3 will continue to support these educational goals.
- Provide a bicycle and pedestrian path that at the completion of all three phases will have created a 1.4 mile trail that connects schools, neighborhoods, Sonoma County Regional Parks Trail and a planned neighborhood park. Phase 2 will construct approximately 1,900 linear feet of this trail, which will support active recreation and encourage physical activity while being located outside of sensitive creek habitat.
- Increase aesthetic beauty by supporting a healthy riparian canopy that will provide a natural visual and acoustic screen throughout the reach.
- Increase the property values throughout the southwest area. Research has shown that creek restoration projects increase property values and projects that include paths with off-street connections and recreational activities have the greatest benefits.
Elsie Allen High School is located adjacent to Colgan Creek, near the Phase I reach, and has been using the creek as an outdoor classroom. The City of Santa Rosa and Trout Unlimited have been providing educational programs to local and culturally diverse elementary and high schools in the Colgan Creek watershed. The program has been funded under two grants from the Urban Streams Restoration Program. The program developed curriculum, made classroom presentations, performed water quality measurements, conducted creek clean ups and plant care days, developed a creek care guide, and created an interactive watershed website: www.colgancreek.org
Funding under the Urban Streams Program will also fund two interpretive signs within the Project area. The sings will be bilingual and promote passive creek stewardship activities. The Phase 1 reach already has interpretive signs highlighting healthy stream ecology and and Pomo basket making with native plants used in the restoration. City funds will provide location/directional signage for all trails users.
Funding and support provided by: