Laserfiche WebLink
<br />Starting water-surface elevations for the Animas River, Junction <br />Creek, and Dry Gulch were taken 'from the Flood Hazard Information <br />report (Reference 2). Hermosa qreek starting water-surface eleva- <br />tions were taken from the Anima~ River at their confluence. All <br />other starting water-surface el~vations were determined by the <br />slope-area method. <br /> <br />Flood profiles were drawn showing computed water-surface elevations <br />to an accuracy of 0,5 foot for floods of the selected recurrence <br />intervals (Exhibit l). <br /> <br />. <br /> <br />The flood profiles shown in thi~ report are based on the effects of <br />flow through unobstructed hydraulic structures and are, thus, con- <br />sidered valid only if these str4ctures remain unobstructed and do <br />not fail. <br /> <br />. <br /> <br />Elevations for small streams that run parallel to Vallecito Creek <br />and Grimes Creek were taken from the corresponding profiles for <br />those two streams. <br /> <br />For all streams studied by appr~ximate methods, the slope-area <br />method was employed to obtain f~ood elevations, <br /> <br />All elevations are referenced to the.National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks used in the study <br />are shown on the maps. <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />A prime purpose of the National Floo9 Insurance Program is to encourage <br />State and local governments to adopt!sound flood plain management pro- <br />grams. Each Flood Insurance Study, therefore, includes a flood boundary <br />map designed to assist communities in developing sound flood plain <br />management measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national $tandard without regional discrimina- <br />tion, the 100-year flood has be~n adopted by the Federal Insurance <br />Administration as the base floo9 for purposes of flood plain manage- <br />ment measures. The SOO-year fl~od is employed to'indicate additional <br />areas of flood risk in the county. For each stream studied in <br />detail, the boundaries of the 100- and SOO-year floods have been <br />delineated using the flood elevations determined at each cross <br />section; between cross sections~ the boundaries were interpol~ted <br />using topographic maps at scale~ of 1:1,200, with a contour interval <br />of 2 feet, 1:2,400, with a cont~ur interval of 2 feet; 1:4,800, with , <br />a contour interval of 2 feet; ard 1:24,000, enlarged to 1:12,000, <br />with a contour interval of 20 f~et (References 10, 11, 12, and <br />13). Areas studied by approximate methods were delineated <br /> <br />12 <br />