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<br />" <br /> <br />.' <br /> <br />~ECE!"1!!;I <br /> <br />SEP 21 '83 <br /> <br />APPENDIX B <br /> <br />COLORADO ,//,'1':,:: <br />CONSERVA" "e'" <br />BOA:1~ <br /> <br />GALESVILLE DAM BREACH INUNDATION STUDY <br /> <br />INTRDDUCTION <br /> <br />Galesville Dam is located at river mile 60 on Cow Creek in <br />Douglas County, Oregon. Constructed in 1985, the dam is a 160 <br />foot high roller compacted concrete (RCC) structure impounding <br />42,225 acre-feet of water. The purpose of this study was to <br />determine the ext~nt of flooding that would result should the <br />dam fail for some reason. This is not intended to reflect upon <br />the integrity of the darn. <br /> <br />DESCRIPTION OF STUDY AREA <br /> <br />The area studied begins at the dam and continues for 107 river <br />miles downstream to the confluence of the North and South Umpqua <br />Rivers, about 5 miles northwest of the City of Roseburg. The <br />study was terminated at the confluence because it was determined <br />that a fair weather dam failure flood would be confined to <br />bankfull conditions at this location, and real time flood <br />warning should be available. <br /> <br />) <br /> <br />For purposes of discussion, the study area is broken down into <br />four reaches: <br /> <br />I. Upper Cow Creek from the dam to about 2 miles <br />downstream of the City of Glendale. <br /> <br />2. Cow Creek Canyon from Upper Cow Creek to about 5 <br />miles upstream of the City of Riddle. <br /> <br />3. Lower Cow Creek from Cow Creek Canyon to the <br />confluence with the South Umpqua River, about 2 miles <br />downstream of the City of Riddle. <br /> <br />4. South Umpqua River from the confluence with Cow <br />Creek to the confluence with the North Umpqua River. <br /> <br />1. Upper Cow Creek <br /> <br />From the darn to near Interstate Highway 5 at Azalea, Cow Creek <br />is confined to a rather narrow valley. The creek channel is on <br />the order of 10 feet deep and 100 feet wide. The valley floor <br />is about I,DOO feet wide with cover ranging from grassy fields <br />to moderate forest and brush. The area is rural in nature and <br />lightly populated. County Road No. 36 runs through the area. <br /> <br />From Azalea to Glendale, the valley floor is much wider, being <br />on the order of one half mile wide. The creek channel is <br />somewhat wider and about the same depth as that upstream. The <br />valley floor has cover ranging from grassy fields to brush. The <br /> <br />B 1 of 11 <br /> <br />., <br />