Water Resources Collections and Archives

We assessed the success of Green Valley River Restoration Project, specifically assessing sedimentation and channel stability. The major objectives of the restoration were to provide flood control by constructing a two terraced channel, re-plant riparian corridor with native species, and mitigate for 1.89 acres of seasonal wetland lost to development. We attempted to compare project conditions after a major flow event in 1995 (second year after project completion) with those of the most recent (2002) surveys. Surveying methods were inconsistent from year to year making direct comparison of surveys difficult. In general, the two-terrace channel has remained relatively stable and successfully conveyed flood waters downstream. Erosion and deposition within the channel are less stable because of excessive sediment loading from upper watershed. Severe sedimentation along Hennessey Creek, a tributary to Green Valley Creek, caused damage to private property within the project reach during flood events. Litigation ensued and one of the outcomes was the development of new watershed scale management strategies. Some of these new strategies included improving farming techniques in the upper watershed to minimize sedimentation, conducting more scientific studies to assess sources of sediment, continuing monitoring creeks throughout the watershed, and consistently revising requirements developers must meet to build within the river corridor. Overall we see Greek Valley Creek as a successful project, one where the shortcomings of the project (sediment transport considerations) will provide useful learning tools for future management.