Cow Creek and Mill Creek Riparian Mapping and Conditions

Cow Creek and Mill Creeks are east-side tributaries to the north Sacramento River that provide important habitat for native fish and other wildlife. To-date however, both watersheds have lacked detailed and spatially explicit information on the existing vegetation and ecological condition of the riparian corridors. To address this information gap and to help guide future restoration and enhancement efforts, this project was initiated with three primary goals: (1) map the riparian and adjacent vegetation; (2) assess conditions of the riparian corridors; and (3) develop recommendations in the form of an annotated list, on priority action areas for restoring or enhancing riparian vegetation. This project is funded through the Anadromous Fish Restoration Program administered by the US Fish and Wildlife Service. To map vegetation along the river corridors for Mill and Cow Creeks, we used a combination of remotely collected and field collected data. For three weeks in 2013, a field crew surveyed vegetation types at 244 points and performed more in-depth surveys of riparian conditions at 81 points in both watersheds. These field data provided ground truthing information for the draft vegetation map and information on riparian conditions. A draft vegetation map of the riparian corridors was created using aerial imagery from a variety of sources. Two attributes associated with riparian vegetation that are new or unusual components of vegetation maps were included in this effort: vegetation overhang along the stream channel and meadow type based on a hydrogeomorphic classification for the Sierra Nevada, published in 2011. Ground truthing demonstrated that the draft vegetation map had an overall accuracy of 89%. As a first step in the riparian conditions assessment, the riparian corridor within both watersheds was divided into reaches with consistent geology, hydrology and surrounding land use. Within these areas, information from the mapping effort, field surveys, technical documents and other spatially explicit data were used to assess riparian conditions. We used eight structural characteristics discernable using remote imagery or GIS data layers as indicators of riparian condition and then applied a consistent scoring scheme to develop advisory condition quantifications for each condition reach. These were used with other site-specific and less easily quantified information to develop final condition scores for each condition reach. Reaches with lower condition scores were more closely examined using remote imagery and other information sources to identify, in an annotated list, high priority areas for restoration and enhancement in Cow Creek and Mill Creek watersheds.