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<br />GLENWOOD SPRINGS FIS <br /> <br />1. Introduction <br /> <br />A. Purpose <br />The purpose of the study is to delineate the 100-year and 500-year floodplain <br />hazard associated with the Colorado and Roaring Fork Rivers, and determine the 100- <br />year floodway in the City of Glenwood Springs. The study reach includes a total of7.0 <br />river miles. The study reach along the Colorado River begins 2.9 river miles below the <br />confluence with the Roaring Fork River and extends for 0.9 river miles upstream of the <br />confluence. Along the Roaring Fork River the study reach extends 3.2 river miles <br />upstream ofthe confluence. This study will assess potential flood hazards from the <br />Colorado and Roaring Fork Rivers within the city limits. <br /> <br />B. Authorization <br />Work order request (Request No: BZ 457-97-1) from Water Resource Branch, <br />Planning Division, US Army Corps of Engineers, Sacramento District. <br /> <br />2. Scope <br /> <br />A. General <br />This report describes the technical studies done to prepare flood plain maps for <br />the two major rivers in the City of Glenwood Springs. Hydraulic analysis was done on <br />both the Colorado and Roaring Fork Rivers. The river hydraulics were analyzed using <br />HEC-RAS. This report includes results from this analysis and the resulting floodplain <br />delineations. The study conforms to the Federal Emergency Management Agency <br />(FEMA) Guidelines and Specifications for Flood Hazard Mapping Partners (Web URL: <br />www.fema.gov/mitltsdlgs_main.shtm). <br /> <br />3. Background <br /> <br />A. Description <br />GIenwood Springs is situated at the confluence of the Roaring Fork and Colorado <br />Rivers. The Roaring Fork River flows north and joins the west flowing Colorado River <br />in the vicinity of the confluence. Both rivers have entrenched channels in the valley <br />bottom and are confined by the numerous alluvial fans draining the surrounding mesas. <br />The focus of the flood hazard delineation are at the locations where potential flooding <br />may inundate development located on the river terraces. <br /> <br />The original scope in 1997 included an effort to delineate flooding caused by <br />debris flows on the numerous alluvial fans that surround Glenwood Springs. Volume I of <br />this report determined the hydrology for 42 watersheds that debouch into the city. <br />Review of the resulting debris hazard floodplains revealed that there is considerably <br /> <br />1 <br /> <br />