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<br />days and spring showers give rise to high flood potential. Heavy <br />thunderstorms through the summer and fall have caused flash floods. <br /> <br />Information on historical flooding on the Mancos River in and around <br />the Town of Mancos is available primarily fram newspapers. Records <br />from an early stream-gaging station located 2 miles east of town <br />are available from the Office of the State Engineer for a limited <br />number of years beginning in 1921. Gaging stations are located <br />above the town on the Mancos, West Mancos, Middle Mancos, and East <br />Mancos Rivers. <br /> <br />Although a continuous gage record for the river at Mancos does not <br />exist, newspaper records and area stream gage records indicate <br />that high water and major flood events have occurred since the <br />area was first settled in 1876, and particularly in 1909, 1911, <br />1932, 1937, 1938, 1941, 1944, 1949, 1957, 1973, and 1979. <br /> <br />According to the Mancos Times Tribune, the May 31, 1979, floodflow <br />on the Mancos River of 1,575 cubic feet per second (cfs) was among <br />the largest. This flow was significantly less than the SO-year <br />recurrence interval flood. <br /> <br />The Mancos Times Tribune reported that flood damage from the Mancos <br />River occurred during the floods of 1909 and 1911, causing damage <br />to the post office and various commercial and warehouse structures. <br />In 1957, flood damage was largely to irrigation structures. The <br />floods in May 1973 and May 1979 (1,110 cfs and 1,575 cfs, respec- <br />tively) caused substantial bank erosion in and around Mancos. <br /> <br />There is little flood history information available for Chicken <br />Creek. No stream records exist for the stream. <br /> <br />2.4 Flood Protection Measures <br /> <br />There are no existing flood-control structures in the study area, <br />or upstream of the study area, which could reduce the present flood <br />hazard. However, the U.S. Army Corps of Engineers (COE) completed <br />bank protection work along the Mancos River banks at the sewage <br />lagoons in December 1973. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />For the flooding sources studied in detail in the community, standard <br />hydrologic and hydraulic study methods were used to determine the flood <br />hazard data required for this study. Flood events of a magnitude which <br />are expected to be equaled or exceeded once on the average during any <br />10-, 50-, 100-, or 500-year period (recurrence interval) have been selec- <br />ted as having special significance for flood plain management and for <br />flood insurance rates. These events, commonly termed the 10-, 50-, 100-, <br /> <br />5 <br />