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characteristics. The veracity of this point is based on historical documentation provided by area newspapers. Newspaper records, as well as stream gage records, indicate that high water and major flood events have occurred since the area was settled in 1876, particularly in 1909, 1911, 1932, 1937, 1938, 1941, 1944, 1949, 1957, 1973, and 1979. Flood loss in the West Dolores River, Dolores River, and Lost Canyon Creek is usually limited to damage of bridges and irrigation structures. Frontal type rainstorms in October 1911 caused the largest flood of record in the drainage areas of the Dolores and West Dolores Rivers, flooding much of the Town of Dolores. The Mancos Times Tribune reported that the floods of 1909 and 1911 caused damage to the Post Office and various commercial and warehouse structures. In 1957, flood damage was limited to irrigation structures. Floods in May 1973 and May 1979 0,110 and 1,575 cubic feet per second (cfs), respectively), caused substantial bank erosion in and around the Town of Mancos. The May 31, 1979, flow was significantly less than the SO-year recurrence interval flood (Reference 2). 2.4 Flood Protection Measures Construction of rock and dirt embankments near bridges throughout the county by the Montezuma County and the Colorado State Highway Department crews, and bank protection work along the Mancos River banks at the sewage lagoons near the Town of Mancos completed by the COE in December 1973, constitute the only existing flood structures in the study area which could reduce the present flood hazard. 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this Flood Insurance Study. Flood events of a magnitude which are expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as having special significance for floodplain management and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, or 500-year floods, have a 10, 2, 1, and 0.2 percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long term average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than one year are cons idered. For example, the ri sk of having a flood which equals or exceeds the 100-year flood (1 percent chance of annual exceedence) in any SO-year period is approximately 40 percent (4 in 10), and for any 90-year period, the ri sk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community at the time of completion of this Flood 5