Don't forget Mt. Hood. The Sandy River is named as such because of a lahar from a decade prior.
Eruption-related lahars and sedimentation response downstream of Mount Hood: Field guide to volcaniclastic deposits along
the Sandy River, Oregon -- https://volcanoes.usgs.gov/vsc/file_mngr/file-59/Pierson%20e...
> The Sandy River was originally named the Quicksand River by Lewis and Clark in 1805 (Moulton and Dunlay, 1990). Expedition members noted that the river (a) was ~275 m wide at its mouth and for several kilometers upstream on the delta (30-150 m wide there today); (b) had a number of mid Channel Islands; and (c) had flow which was turbid and very shallow (resembling the Platte River in Nebraska, they noted). It was given its name because "the bed of this stream is formed entirely of quick sand."
https://pubs.usgs.gov/fs/old.2000/fs060-00/fs060-00.pdf
> What happened? The answer lay 50 miles away at Mount Hood. An eruption in the 1790's caused a tremendous amount of volcanic rock and sand to enter the Sandy River drainage. That sediment was still being flushed downstream when Lewis and Clark saw and named the river. Since 1806, the river has removed the excess sediment from its channel.
