Emergency Fish Passage Project on the Lower Van Duzen , 2001-2016 Beginning in November, 2001, after a particularly disastrous migratory riffle stranding event for early Chinook salmon spawners, that killed over 130 fish, pro-active measures were initiated by fishery management and regulatory agencies, and gravel operators, to prevent future salmon mortality incidences.

Many sites in the widened reaches along the lower Van Duzen River (e.g., below the confluence) have experienced flood flows and channel aggradation, and resultant stream bank erosion. Thus, the channel widening and associated sediment accumulations contribute to detrimental impacts to both land owners and to aquatic habitats. In addition to a loss of valuable riparian land from erosion, channel widening and excessive sediment accumulations have reduced the reach’s value to salmonids by filling in scarce pool habitat and forming very wide, shallow “critical” riffles that typically dry in late summer. During summer, juvenile rearing habitat is extremely scarce. Even worse, during fall migration when initial surface flows begin, these conditions can create shallow, braided ‘distributary’ channels inadequate for successful adult salmonid passage upstream to spawning reaches. These wide shallow channel reaches and critical riffles are common along the lower Van Duzen River.

Van Duzen River channel widens at river mile four (upper reach of delta), near town of Carlotta and the confluence of Yager Creek with Van Duzen River. Photo from KRIS coho. The wide shallow river condition creates a re-occurring problem for fish passage into the Van Duzen from the . After the first rains of fall, this reach forms wide, braided shallows that impede upstream passage of fall migrating Chinook salmon. In the fall of 2001, over 130 adult Chinook salmon were stranded in a single night and died along the shallow lower mile of river as they tried to migrate up the Van Duzen. Each year since the incident, the river bed has been modified as needed during gravel mining operations to create a single-thread fish passage channel up to one-half mile in length. The channel is based on analysis and design by NOAA Fisheries, with input from CHERT. The Department of Fish and Wildlife controls upstream access into the constructed channel with three exclusion culverts placed in a gravel berm, or “coffer dam,” that prevents migrating fish from entering the Van Duzen from the Eel River during flows less than 150 cfs, which are inadequate for safe passage. When flows reach ~160 cfs, and the three 36” ‘exclusion’ culverts are at their full capacity, the pipes are removed, safely allowing salmon to move upstream into the constructed channel and further upstream throughout the river system. This cooperative fish passage project has been highly successful in eliminating fish stranding mortalities since its adoption. It has also required considerable effort by all involved, which includes monitoring the results in terms of successful upstream access by spawners. Channel conditions in the treatment reach are monitored on an annual basis to determine if the berm and pipes are needed to address likely passage hazards. If channel cross sections and profiles indicate there is little chance of braiding conditions forming, the project is not installed. Gravel extraction planning to help avoid hazardous channel conditions from forming is also conducted. The project has led to overall modified extraction methods based on the need for establishing safe fish passage. For many years now, the gravel harvest has been done primarily by excavator trenching. This has resulted in an overall lowering of the channel elevation into a concave shaped cross-section, through the middle of the lower bar to the extent that in the last two years the coffer dam and pipes have not been deemed necessary, and fish passage has been successful without incident. However, in years of dry river channels, coupled with poor rainfall in early fall, or worse, pulsing rain events that attract spawners, but are not adequate to provide safe fish passage, the team will consider the installation of the project. When conditions create a high risk of stranding events, the fish passage project is a tool that will be used on an adaptive basis and be put in place based on analysis of the situation and variables, and when needed is of proven value to pass spawning salmonids.

Van Duzen River dry channel causes fish stranding at early, low, attraction flows. Downstream view to RR and Highway 101 bridges, and beyond to confluence with Eel River.

Looking downstream to Van Duzen bridges during 2001 stranding event.

Sadly, ninety-six (96) Chinook spawners headed for Van Duzen tributaries

(above) View upstream at excavated access channel with placed exclusion culverts; (below) view downstream with culverts removed to allow fish passage into Van Duzen River at flows of > 150 cfs.

Scott Downie Short Bio

Scott retired as a Senior Environmental Scientist Supervisor for the California Department of Fish and Wildlife (CDFW) in 2014. He has worked on salmon and steelhead management, habitat restoration, and watershed analysis for over thirty years. The last decade of his career with CDFW, he managed a multi-disciplinary, large scale watershed assessment program that investigated the status of watershed processes and conditions of salmonid catchments the length of coastal California. A series of assessment reports were produced and are available (see: coastalwatersheds.ca.gov), including the Van Duzen and other Eel River system subbasins.

He is a native of Humboldt County and grew up fishing and/or guiding on the SF Eel River and other north coastal streams, beginning as a youth prior to the flood events of the mid-twentieth century. Over the years, he has seen much change occur and recur in the Eel and its tributaries as land use and natural forces combine to continually alter the lands and streams of the system at several scales. Now with more time to fish, Scott likes to travel to fly fish, especially for tarpon. At home, he is on the river most days either angling, or simply enjoying the interactive energy of the catchment and its streams.

Contact information:

Phone: 707.496.2298 [email protected]