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<br />PART II <br />NARRATIVE REPORT: <br />DESCRIPTIVE AND DESIGN INFORMATION <br /> <br /> <br />A. Description of project Site_ <br />The T~n of Lake City is located in a valley formed by the Lake Fork <br />of the Gunison, on a relatively flat terrace (ancient flood plain) ,with steep <br />mountain slopes rising on either side. Henson Creek emerges from a steep <br />walled canyon on the west side of Town and joins the Lake Fork of the <br />Gunnison approximately 1700 feet downstream. (see map, p. 111-4). <br />Within the proj ect site, Henson Creek flows in a well defined <br />trapezoidal shaped channel, apprax imately 50 feet wide with stream banks <br />4 to 5 feet high on either side. Water depth during normal flowS is 1 to 2 <br />feet deep. Stream gradient is about 1.2%. The channel substrate consists <br />primarily of strei'l'11 deposited cobbles; there are very few large boulders <br />or flood debris in the channels. Vegetation along the bank consists <br />primari]y of occasional scattered trees and brush. <br />Average annual flow on Henson Creek is 107 cfs. The 100 year flood <br />has been calculated at 2300 cfs and the 500 year flood has been calculated <br />at 3300 Lfs. <br />The north bank is partial]y protected by a levee. The condition of <br />this levee is as follows (stations start at bridge): <br />Location Information <br /> <br />o + 00 to 3 + 50 <br /> <br />Levee is in poor condition with <br />sub- standard freeboard and top <br />width. <br /> <br />3 + 50 to 5 + 00 No existing levee. <br />5 + 00 Critical channel section with <br /> marginal conveyance. <br />6 + 00 to 7 + 00 Downstream I imits of Corps of <br /> Engineers emergency works. <br />7 + 00 to 10 + 00 Existing levee system. <br /> <br />lI-l <br /> <br /> <br />- <br />