Evaluation of Riparian Restoration to Enhance Anadromous Fish Habitat along a Napa County Stream
Understanding the specific conditions that influence successful riparian revegetation can assist projects in meeting their success criteria and ultimately improve habitat for fish and wildlife species. This paper examines a Napa County rangeland stream restoration project designed to enhance habitat for steelhead and other anadromous fish species, and compares the success of revegetation plantings and complementary instream improvements under various installation methods and locations. Though these results are likely site-specific, they provide a reference point to guide future riparian revegetation efforts in the project region.
Factors that appear to result in successful riparian restoration for this project include irrigation installation, placement of plantings in shaded areas or under existing riparian canopy, placement of plantings between the top of bank and toe of channel, exclusion of livestock grazing during establishment of plantings, installation of browse protection, and utilization of plantings of coffeeberry (Rhamnus californica), western spicebush (Calycanthus occidentalis) and oaks (Quercus sp.) along the top of bank as well as California wild rose (Rosa califomica), dogwood (Comus sp), cottonwood (Populus sp.) and Oregon ash (Fraxinus latifolia) along the lower portions of the stream banks. Instream activities, such as removal of low flow barriers to fish passage and creation of pools, enhance existing steelhead habitat. However, additional constraints such as altered hydrology resulting from the original instream structures, and wildlife herbivory can decrease effectiveness of riparian revegetation efforts. Without the additional habitat elements provided by riparian vegetation, the value of instream enhancements may be reduced.