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<br />53 <br /> <br />acre-feet of water. The flooding that occurred in the Willamette basin was all <br />due to local runoff below the storage projects. <br />Downstream of Foster on the mainstem of the Santiam River is the <br />Jefferson gauge. At this site, the flood hydrograph was rising very fast and <br />indicating a 200-year event. Flooding became heavier in the north. During <br />a six-hour period on Thursday, February 7, the precipitation gauge at Foster <br />Dam registered two inches of rain during a six-hour period. In the southern <br />portion of the Willamette Basin, the flooding and rainfall was less than in the <br />North. South at Hills Creek Dam the maximum rain period was only 0.4 inch <br />on February 8. <br />After the flood was over, the Corps of Engineers estimated that the stage <br />and damage reductions due to Corps of Engineers reservoir operations were <br />significant. At the gage at Eugene, the Corps estimated that stage reduction <br />was nine feet, reducing potential damage by $195 million. Further down- <br />stream at the Oregon state capitol of Salem, the Corps estimated a stage <br />reduction 71h feet and damage reduction of $280 million. Within the state of <br />Oregon and at the highly developed Portland-Vancouver metropolitan area <br />total damages were estimated to have been reduced by $1.14 billion. <br /> <br />Henriksen <br /> <br />Modeling <br /> <br />The North Pacific Division Corps of Engineers, in coordination with the <br />National Weather Service River Forecast Center, uses the Streamflow <br />Synthesis and Reservoir Regulation (SSARR) model, which is a hydrologic <br />routing model that is initiated at 4:00 a.m. every day. The first three days of <br />the forecast are in six-hour time steps, and the next two days are daily time <br />steps. The River Forecast Center (RFC) uses six. hourly quantitative <br />precipitation forecasts (QPF) developed by the National Weather Service as <br />input to the inflow forecast portion of the model. The RFC also uses routing <br />parameters to simulate soil saturation in particular basins. Once the individual <br />basin inflows are developed, the Corps of Engineers then overlays reservoir <br />regulations at all the projects in the region to develop the best operational <br />scenario to achieve maximum flood reduction in the Portland Harbor. <br />Overall, forecasting was quite good. As the QPF was updated, the basin <br />inflow forecasts may have been resubmitted. There was a discontinuity when <br />the QPF was updated and the regulation 'resubmitted during evening or <br />nighttime hours, since the regulation could not be re-initialized to any time <br />other than 4:00 a.m. This was particularly troublesome on the lower <br />Columbia River, where many side streams flowing into the Bonneville and <br /> <br />Forecast <br />