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. . 1914 - June 2 1955 1916 1957 - June 29 1918 - August 3 1965 - June 24 1919 - August 1 1966 1921 - June 6 1969 - May 7 1923 - June 9 1973 - May 5 In response to the flood hazard in Boulder, over thirty studics have been conductcd for Boulder Creek since 1910.173 This number docs not include the theses and dissertations which have addcd valuable information on Boulder's floods,179 Although the stream gauges wcrc not in operation during the May 31, 1894 flood, it is gcnerally agreed that event was the flood of record for the creek. In addition, that flood has been estimated as the 1 % or 1 aD-year flood. 180 I t is important to remember that a flood of that magnitude has a 1 % probability of occurring and being equalled or excceded in any year. The discharge estimates for that event were made by the Boston engineering consulting firr.1 of Metcalf and Eddy in 1912,181 Although thcy made their calculations eighteen years after the flood, they used a portion of the stream near Fourth Street that had remained stablc after the 1894 flood. . The Most reliable record of extreme flood level was thClt obtained through the courtesy of the officials of the Denvcr, Bouldcr and Western Railroad Company, upon one of its wooden trestle bridges crossing Boulder Crcek in the vicinity of 4th Street. herc the rivcr cross-section is fClirly uniform in character, for a considerClble distance above and below the trestle. The slope is approximately 1.1%. The reported depth was about 10 feet, giving a cross-section of approximately 700 square feet at this flood level. [Later reports indicate an area of about 800 square feet, and that this depth may have been as much as 11 feet). According to the United States Geological Survey (1960) and the Arr.1Y Corps of Engineers (1969) the Metcalf and Eddy report is reliable.183 Previous to those reports, Junius Henderson's 1921 transmittal to the Boulder Planning and Parks Commission concerning the channelization of Boulder Creek mentioned the credibility of the study. 184 Assisted by photographers and engineers he made investigations of the 1894 flood for the City of Boulder. In 1921 he responded to the Metcalf Clnd Eddy report in the following way: . Metcalf and Eddy's estimatc of from 12,000 to 13,500 feet is conservative, and doubtless approximately correct. Being particularly interested in erosion, I have studicd all the floods of Boulder Creck since 1892, except one, I believe, and. so have personal knowledge of their relativc volumes. Pioneers who were interviewed in 1894 agreed that the flood of 1864 was approximately equal to that of 1894, so there is