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Post-Project Appraisal of Arroyo Viejo Creek Improvement Project, Oakland, California

  • Author(s): Cousins, Mary
  • Storesund, Rune
  • et al.
Abstract

Our Post-Project Appraisal assesses the performance of the Arroyo Viejo Creek Improvement Project, located in Oakland, Alameda County, California. We evaluated the project based on seven goals identified by the lead design firm Wolfe Mason Associates in project planning documents, though most of the goals did not have identified targets and/or quantifiable metrics. Two clear goals evaluated in this Post-Project Appraisal were geomorphic streambank stability and riparian habitat enhancement through the replacement of non-native plant species with native species. To assess geomorphic stability, we surveyed the site and compared current conditions to designed and constructed conditions. Also, we conducted a vegetation survey to quantify the success of planted native vegetation. Three years after its completion, the Arroyo Viejo Creek Improvement Project has a mixed outcome. One of the key goals of the project was habitat enhancement; there seems to be an unstated assumption that native vegetation recovery alone would signal this improvement. The assemblage of native vegetation is well established and represents about 50% of the vegetative cover, but its growth lags behind the target level of 70% cover after three years, and invasive non-natives are a continuing threat. Another key goal, channel stability, is being met throughout most of the site, but there are regions of localized scouring that indicate insufficient bank protection. Finally, invasive aquatic vegetation on the site (primarily watercress) is capturing trash, potentially degrading water quality as a result.

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