Thursday, March 22, 2018

Benton County Water Levels

As mentioned in the last post, steamboats plied the Willamette to Corvallis from 1851 to 1918.  Water levels so low that the boats scraped bottom were a common problems, especially in the summer months. Winter's high water also created problems because there were no flood-control dams on the river prior to the 1940s. In years with especially heavy rains or rapidly melting snow cover, the volume of water increased and the river would overflow its banks as it did in 1916 and 1923.

In recent years, the peak flow of the Willamette River at Corvallis has been between 56,400 cubic feet per second  (cfs) in 2010 and 77,100 cfs in 2016.  Anything more than 83,000 cfs is considered a flood and anything over 142,000 cfs would result in a “major flood.”  In 1916, the peak flow in February was 165,000 cfs. The river flooded a section of the Oregon Electric Line near Corvallis.  This photo shows the extent of flooding looking east from the Van Buren bridge.

The water was even higher during the 1923 flood as the peak flows was 206,000 cfs.
1923 flood

The flood waters carried many downed trees into the river.  These snags could catch in the paddle wheel or puncture a hole in the bottom. Also, as the Army Corps of Engineers noted, “The water was so thick with mud as to render it impossible to discern the positions of snags below the surface.” Floods also changed the location of sandbars and relocated the main channel, causing difficulties for even the most experienced pilots. Beginning in 1870, the Army Corps of Engineers began removing these snags. 

By Martha Fraundorf, Volunteer for Benton County Historical Society, Philomath, Oregon

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