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I. I I I I I I I I I I I I I II I I I :1 distribution. Input data for the program consisted of 43 years of uninterrupted data collected at the gage station below Rico. The 100-year and 500-year peak annual discharges determined by this method are 2655 cubic feet per second (cfs) and 3183 cfs, respectively. It is likely that the flood magnitudes determined by this method underestimate the true magnitude-probability relationship because the relatively short time period of the data does not include the two largest historic floods from an observation period of about 120 years. Flood History The largest flood events in Rico's history occurred in June 1884 and October 1911. Flooding on these dates was widespread throughout the San Juan region. Neither of these floods are represented by discharge data. Information on the 1884 flood is scarce. Newspaper accounts describe farmers coops floating down the river (ref. 1). The 1911 flood destroyed 11 houses, 1 stable, the city feed yards and every bridge in Rico (ref. 2). The railroad yards were "badly washed, cars overturned and other damage done" (ref. 3). Photographs show that both the Dolores River and Silver Creek caused extensive damage (ref. 4). Hydraulic analyses indicate Dolores River discharges of at ieast 8000 cfs would be required to inundate the former location of the train depot. Comparison with Other Basins Drainage area-discharge relationships from similar basins were used to estimate peak discharges for Silver Creek because discharge data are unavailable. Area-discharge relationships were also used to help estimate the 500-year flood discharge for the Dolores River due to data limitations. Table 1-1 shows the peak discharges reported in FEMA flood studies from other regional basins. The ratios of peak discharge to area for the Dolores River Basin also shown in Table 1-1 are relatively consistent. The higher discharge-area ratios for Chicken Creek and Junction Creek can be explained by 2