color photos by Joe Hull
black and white photos courtesy of James Taylor
June 2002
Squire Creek is a major tributary to the North Fork of the Stillaguamish River, in the central part of the North Cascades near the town of Darrington. Squire Creek occupies a steep sided rocky valley between Jumbo Mountain on the east and Whitehorse Mountain on the west.
The Squire Creek rockslide and debris flow took place around 8 a.m., Monday 25 February 2002, according to Bob Norris (the Darrington Ranger District and the Everett Heralad reported the slide as occurring on 8 March). The landslide originated as a rock failure on the north end of the Jumbo Mountain ridge, below Peak 4028 at approximately 3500 feet above sea level. The ridge is made up of fault bounded blocks of metamorhposed gabbroic to dioritic rocks, slates, and ultramafites and serpentinites. The rockslide/rockfall evolved into a debris flow as it raced downhill, "bulking up" on vegetation, soil, colluvium, and older avalanche and debris flow materials. The debris flow split into two main channels separated by about 50 meters, and then spread out as the bottom of Squire Creek valley was reached at about 1200 feet asl. The debris flow surged across Squire Creek, filling the channel and knocking down trees on the opposite bank. Squire Creek was (and is) dammed on the upper side; the creek has cut a new channel into the debris flow deposits since 25 February.
I have not made a volumetric estimate, but this is a monster slide/flow. It is really impressive. Bob Norris reports an estimate of the volume between 50,000-100,000 cubic meters. Bob Harp of the USGS Landslide program in Denver has visited the site.
Squire Creek is an important salmon spawning stream. It will be interesting to see the impact on salmon.
The amount of shredded conifers in the debris flow deposit is very high; 10-20% by volume in many places. The vegetation is rotting rapidly and the whole place smells like a pulp mill. In several localities, an oily scum is oozing from the debris flow, and small ponds of organic-rich water have interesting algal colonies growing on top. Rotting vegetation may influence the local water chemistry.
To get to the Squire Creek slide, exit towards Arlington/Highway 530/Mountain Loop Highway off of I-5, and continue through Arlington towards Darrington. As you are entering Darrington, take a right hand turn onto Fullerton Street at the pharmacy, and go straight ahead to the stop sign at the T. Turn right onto Squire Creek road, which starts off as blacktop, but then turns into gravel; some potholes, but passable with a common passenger vehicle. Follow the gravel road to the end and park at the barrier. Hike one quarter of a mile up the road to the slide. Follow the bootprints onto the slide.
Don't go onto the slide if it's raining, there is still a lot of loose debris in the slide paths. The slide surface is very rough, wear ankle protection.
PHOTO 1. Looking southeast towards Jumbo Mountain ridge up the
northern scar channel. Source of initial rockslide is at head of
scar path next to puffy cloud. The southern debris channel is just
visible in lower right
PHOTO 2: looking up the northern channel. bedrock exposed in middle of picture. debris flow has dug down into older deposits.
PHOTO 3: Greg Langkamp, math instructor at SCCC, admires debris flow deposit at base of northern channel. Thickness of the deposit here: 5-10 meters.
PHOTO 4: Close up of abraded woody debris.
PHOTO 5: accumulation of woody debris at southern end of debris fan.
PHOTO 6: Greg Langkamp, math instructor at SCCC, stands atop the
logjam where the debris flow ended.
Part of Squire Creek flows under this logjam and behind Greg and then
to the right downstream.
PHOTO 7: Squire Creek is dammed up to form a small lake at the south
end of the debris flow.
Trees still standing at the edge of the debris flow are drowned and
will die soon.
Katy Ball, Joe Hull (facing camera), Greg Lankgamp, Joann Moreno and
Soko Tarumi
see that Squire Creek has cut down about 5 meters into the debris flow
at its northwest corner.