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<br /> <br />'- "'~ <br /> <br />time of completion of this study. Maps and flood elevations will be <br />amended periodically to reflect future changes. <br /> <br />3.1 <br /> <br />Hydrologic Analyses <br /> <br />" <br /> <br />Hydrologic analyses were carried out to establish the peak discharge- <br />frequency relationships for each flooding source studied in detail <br />affecting the community. <br /> <br />Hydrologic data were developed from the results of a frequency <br />analysis. Flow-frequency parameters were developed from the Manual <br />for Estimating Flood Characteristics of Natural-Flow Streams in <br />Colorado (Reference 3). Floods larger than the SOO-year flood <br />are possible, but the combination of factors necessary to produce <br />such large flows would be extremely rare (Reference 1), <br /> <br />Peak discharge-drainage area relationships for the flooding sources <br />affecting the City of Walsenburg are shown in Table 1. <br /> <br />3.2 Hydraulic Analyses <br /> <br />Analyses of the hydraulic characteristics of flooding from the <br />sources studied were carried out to provide estimates of the eleva- <br />tions of floods of the selected recurrence intervals. <br /> <br />Standard hydraulic methods were used to determine the magnitude of <br />floods of the selected return frequencies. Cross sections were <br />developed using information obtained in the field and scaled from <br />topographic maps. The starting water-surface elevation for the <br />Cucharas River was obtained by the slope-area method. Water-surface <br />elevations for floods of the selected recurrence intervals were <br />computed using the U.S. Army Corps of Engineers HEC-2 step-backwater <br />computer program (Reference 4). <br /> <br />The flood elevations shown on the profiles are thus considered <br />valid only if hydraulic structures remain unobstructed, operate <br />properly, and do not fail. <br /> <br />Data for floods of the 10- and 50-year recurrence intervals on the <br />North Walsenburg Flood Control Dam Overflow were not included in <br />the existing data used to prepare this study. <br /> <br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks used in this study <br />are shown on the maps; descriptions are presented in Elevation <br />Reference Marks (Exhibit 3). <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIOOS <br /> <br />The NFIP encourages State and local governments to adopt sound flood <br />plain management programs. Therefore, each Flood Insurance Study <br /> <br />10 <br /> <br />I <br /> <br />, J <br />