Stulls Falls
Bedrock Trench Cutting
BACKGROUND
Stulls Falls is a two step falls at river mile 16 on the West Fork Millicoma River in the Coos basin on the Southern
Oregon Coast. The falls have a total elevation differential of over 20 feet and there are nearly 60 miles of habitat with
good to excellent intrinsic potential upstream for coho, fall chinook, and winter steelhead. The falls have always posed a
notable restriction for adult fish passage and a significant migration delay for steelhead and coho. There have been
numerous alterations to Stulls Falls since 1950, such as dynamite blasting and fishway construction. In 1952, ODFW
constructed a fish ladder around the lower, taller falls, and a concrete weir was later constructed below the upper falls to
improve fish passage. This weir blew out during the 1996 flood and a bedrock plate collapsed into the main jump pool of
the upper falls, further impeding adult passage due to increased jump height and velocity at the falls. Adult migratory
passage has been further hindered numerous times by insufficient winter flow for coho and steelhead during critical
winter migratory periods. For more than the last 20 years, the upper falls were a complete barrier to chinook migration,
a significant obstacle to coho, and a limited obstacle to steelhead. Chinook have been unable to pass above the falls to
spawn due to passable flows occurring less than 18% of the time, all of which occur outside their migratory period, and
they have not been reported upstream of the falls. Passable flows occurred less than 38% of the time for coho;
however, they were often trapped in the pool below during low-flow years and forced to spawn by the hundreds in a
small tributary downstream.
Project Partners
Special thanks to
our generous
landowner!
Mike Vaughan
Project
Contacts
Allison Tarbox, [email protected]
CoosWA Stream Restoration Program Leader
Randy Smith, [email protected]
ODF Fish & Wildlife Biologist
PROJECT DESIGN
Three low-flow trench channels were designed to be carved into the bedrock
ledge of the upper falls. Based on the advice of ODFW fish passage
personnel, the new channels were designed to be 2 feet wide and 1 to 1.5
feet deep. These trench channels allow passage over a wider range of
winter flows (especially flows less than 100 cfs) that have typically occurred
during recent winter migratory periods. After a few attempts of using
expanding grout to fracture the bedrock trenches, the crew primarily used
concrete cutting saws with diamond-tipped blades and a jackhammer to
carve out the trench channels with precision.
Aug 2016
Sept 2016
Low Summer Flows
Nov 2012
Low Winter Flows
POST-PROJECT MONITORING
The new channels now provide routes through the upper
falls that are passable for migrating adults at a wider
range of winter flows as salmonids have not been
observed holding in large numbers as in past years. In
2016, spot check surveys were conducted upstream of
the falls in late October and early November to determine
if chinook were able to successfully navigate over the
falls. In these surveys, 18 female chinook, 8 male
chinook, and 22 chinook redds have been documented
spawning 15 ½ miles upstream of Stulls Falls in the West
Fork and ½ mile up Elk Creek. In the November 4 spot
check survey, numerous adults were spotted in new log
jam habitat constructed by CoosWA in the past 6 years.
Oct 2016