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I I . I . . I I I II I II '. II FLOOD HAZARDS Introduction The purpose of the flood study is to evaluate flood elevations and areas likely to be impacted by floods within the Town of Rico. Flood events of magnitudes which are expected to be equaled or exceeded once on the average during any 100- or 5OD-year period were analyzed. Cross-sections and roughness parameters were selected based on flows of these magnitudes. All elevations in this study are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Three methods were employed to evaluate peak flood discharges for the Dolores River and Silver Creek in this study. A statistical frequency analysis was performed using data for the Dolores River. Historical accounts and photographs of high water elevations and damage caused by flood events without flow measurements were also used to determine flood discharges. Additionally, data from similar drainage basins in the region were considered, panicularly for Silver Creek which is an ungaged basin. Frequency AlUllyses I~ ~ ~ ~ - Peak discharges for the Dolores River were evaluated by applying The U.S. Geological Survey (USGS) Annual Peak Flow Frequency Analyses Program J477 Version 3.7, revised 11-5-81. The reference gage station (USGS 09165000) is located near the Dolores-Montezuma County Line approximately four miles south of Rico. Scotch Creek is the only significant tributary to the Dolores River between Rico and the gage. Silver Creek is another significant tributary which joins the Dolores River near the north Town Limit. Incomplete flow data from a gage located at Rico between 1914 and 1921 were not included in the analysis because these data do not include peak flows. The USGS program generates curve parameters using a log-Pearson Type III 1