A Piece of the Lower Fanno Creek Puzzle

The Site

Size: 5 acres
Stream length: 1,743 feet
First planting: 2018

Tucked between an industrial complex, suburban homes and agricultural land is Bonita Natural Area, near Southwest 74th Avenue and Southwest Bonita Road in Tigard. The site also includes the final stretch of Ball Creek before it enters Fanno Creek. Metro purchased this site along lower Fanno Creek in 2003 with money from the 1995 voter-approved natural areas bond measure. The long-term goal is to complete the Fanno Creek Trail from the creek’s headwaters in the West Hills of Portland to its confluence with the Tualatin River in Durham.


The Challenge

Due to limited funding, this site was largely ignored for many years. Though some native plants and a mix of upland and wetland communities persisted,  non-native plants and invasive weeds had flourished. Bonita Natural Area is surrounded by an urbanized landscape with a relatively high percentage of impervious surfaces from roads, parking lots and commercial buildings, generating faster and higher water flows during storms. The site’s high levels of disturbance, lack of native vegetation on stream banks and high storm flows in Ball and Fanno creeks had resulted in low-quality fish and wildlife habitat, streambank erosion and water quality issues.


The Transformation


Metro, Clean Water Services and the City of Tigard developed a vision for the Bonita Natural Area that includes clean water, improved fish and wildlife habitat and, eventually, a connection to the Fanno Creek Trail system. To achieve this vision, the partners added a mix of diverse native plants, which will filter water and increase soil stability along Fanno and Ball creeks. The plants will also provide shade to cool the water temperature and boost native habitat for wildlife. The plant communities include mixed riparian forest, emergent wetlands and shrub-scrub wetlands. Native species will be the dominant plants on the site. Invasive species control helps with long-term native plant survival.

In order to reduce erosion, improve water quality, increase floodwater storage during storm events and provide aquatic habitat, the partners added habitat logs in the channel and along the floodplain.