For about two years I rented an old farmhouse on Norman Road. We witnessed several floods. Once the floodwaters got all the way up to the base of the house's foundation. Even though that was an impressive amount of water, my little voice wondered “how did this relatively small river carve such a large valley?”
I later learned that in ancient times the geographic land area that drained into the Stillaguamish River, the river’s watershed, covered a much larger area. All the creeks and rivers on the western flank of Glacier Peak, that we now call the Sauk River and Whitechuck River, used to be the headwaters of the Stillaguamish River.
About 13,000 years ago a series of eruptions of Glacier Peak caused lahars (slurries of rock, mud, melted ice, and snow) to race down what are now the Sauk River and the Whitechuck River. When the debris flow reached the flat area near present-day Darrington a log jam formed and dammed up the Stillaguamish River. A lake formed behind the dam/log jam. At some point the lake began draining toward the north and started flowing toward the Skagit River.
To this day, the top of the Stillaguamish River watershed is just west of Darrington (no longer the top of Glacier Peak). It is "missing" its original "headwaters", all the land on the west side of Glacier Peak. That's why some call the Stilly the “headless watershed”.
… and that’s why, way downstream on Norman Road, the size of the river and its valley don’t match up.
For more information: www.mil.wa.gov/uploads/pdf/emergency-management/volcano/glacierpeak.pdf
