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Cross section data for streams in the study area were obtained from w-w r sections were 0 ained by field Dlt::a:;,uI.t::wt::uL. All I>. idges and cu1.erts were measured to obtain elevation data and structural geometry. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a f100dway is computed (Section 4.2), selected cross section locations are also shown on the Flood Boundary and F100dway Map (Exhibit 2). Roughness coefficients (Manning's "n") were estimated by field inspection at each cross section and checked for reasonableness against a standard text (Reference 6). Roughness values for the main channel ranged from 0.034 to 0.070 on the Animas River, from 0.025 to 0.045 on Junction Creek, and from 0.024 to 0.040 on Dry Gulch Creek. Roughness values for the floodplain ranged from 0.060 to 0.080 on the Animas River, and from 0.030 to 0.050 on Junction Creek; a value of 0.050 was used on Dry Gulch Creek. Water-surface profiles developed using the (Reference 7). of the selected recurrence COE HEC-2 step-backwater intervals were computer model Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals. The flood profiles presented in this study are based on of flow through unobstructed hydraulic structures and considered valid only if these structures do not fail unobstructed. Hydraulic analyses were conducted by (Reference 3) and reviewed by the study contractor. the effects are, thus, and remain the COE The hydraulic analyses for the reach of the Animas River from MP 63.000"to--MP-"63.251were-eon<lueted- by" "Goff-"E"g~neering "& -Surveying, Inc. (Reference 1) and reviewed by the study contractor. All elevations are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks used in this study are shown on the maps; the description of the marks are presented in Elevation Reference Marks (Exhibit 3). 4".0 FLOODPLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and local governments to adopt sound floodplain management programs. Therefore, each Flood Insurance Study provides 100- year flood elevations and delineations of the 100- and 500-year floodplain boundaries and 100-year f100dway to assist communities in developing floodplain management measures. 8