Portland District's Willamette Valley flood risk management mission is to save lives and reduce property damage. During the wettest time of the year (mid-November through January), we operate our 13 dam and reservoir projects in the North and South Santiam, McKenzie, and Coast and Middle Fork Willamette river basins to help reduce flooding downstream. We store incoming water during significant rain events, and then release it as river levels subside. River levels may remain high for an extended time after rain events as we release stored water. Whenever possible, we try to keep river levels at or below the “bankfull” levels established by the National Weather Service.
We cannot prevent
floods, but we can significantly reduce the level of floods and the damage they cause. Our dams can regulate about 88 percent of the total basin runoff that reaches the Jasper gauge above Eugene, 42 percent that reaches Salem, and 27 percent that reaches Portland. Since 1996, they have provided an annual average of almost $1 billion in flood damage reduction. Click here for a map of the Willamette River Basin