Flash flood in Whychus Creek shows stream’s natural variability

October 7th, 2013

Originating at the base of Bend Glacier on Broken Top in the Cascade Mountains, Whychus Creek tumbles down through the City of Sisters before flowing into the Deschutes River. As a snowfed, undammed stream, Whychus Creek is subject to large fluctuations in streamflow depending on precipitation and snowmelt.

Two weeks ago, we witnessed just how variable this system can be with a ten year water event resulting from the weekend’s heavy rainfall. Sunday night, water levels in Whychus Creek surged from a seasonal average of around 100 cubic feet per second (cfs) to well over 1000 cfs  in a thirty minute time period. That’s a 1000% increase in streamflow!

“This is an extreme event in Whychus Creek, but not unheard of considering the variable nature of the creek,” said Zachary Tillman, program manager at the Deschutes River Conservancy. “You wouldn’t see this kind of event in the Deschutes River, for example, where dramatic fluctuations in flow are reduced by the porous nature of the geology of the drainage area.

Since the flash flood happened at night, there are no photos. This graph gives a good idea of the quick rise in streamflow that occurred.

Since the flash flood happened at night, there are no photos. This graph gives a good idea of the quick rise in streamflow that occurred.


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