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<br /> <br />~ <br /> <br />ClSe flood outlines and depths may be obtained by <br />projecting elevations from the profiles and flood <br />pl"in reference data outward on the flood plain to <br />match.ng ground elevations. <br />Abrupt changes in water surface elevations <br />I11JY be noted where bridges or other features con. <br />. >tllCt the channel crOSS section. Accumulation of <br />d.!blls at the upstream side of a bridge during <br />flood.ng would increase the upstream flood height <br />more than is shown. <br />Sheet flow of undetermined depth is indicated <br />by croSS !latched areas on the flooded area map. <br />Tllese flows result from Boulder Creek overflows <br />and will follow streets and low areas to return to <br />the creek farther downstream. <br /> <br />VELOCITIES <br /> <br />Flood flow velocities, such as are generated <br />"long Boulder Creek in the study reach, are both <br /><I,mcerous to life and damaging to property and <br />,hould be avoided. Witness the destruction shown <br />by the photos of the 1894 flood. <br /> <br />HAZARDS OF LARGE FLOODS <br /> <br />Tile extent of inundation during large floods as <br />shown on the flooded area maps illustrates the <br /> <br />hazard in the Boulder Creek flood plain. Flow <br />velocities generated are an additional element in. <br />creasing property damage and human danger. The <br />direct damage and danger is compounded by trans. <br />portation and utility disruptions, loss of business, <br />postponed new developments, cleanup expense, <br />and countless other secondary costs. Community <br />awareness of hazards in the flood plain is an im. <br />portant step toward proper flood plain manage. <br />ment. Flood prevention, zoning, building regula. <br />tion, flood proofing, and other measures are the <br />responsibility of local authorities. The Corps of <br />Engineers is available to assist in the interpreta~ <br />tion and use of the information provided in this <br />report. <br /> <br />ACKNOWLEDGEMENTS AND <br />ASSISTANCE <br /> <br />The City and County of Boulder, the Urban <br />Drainage and Flood Control District, and the State <br />of Colorado cooperated and assisted in the prepa. <br />ration of this report. The origin of the 1894 flood <br />photographs, prints of which were found in Corps <br />of Engineer files, is unknown. <br />