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<br />MEMORANDUM <br /> <br />. <br /> <br />COLORADO WATER CONSERV A nON BOARD <br />DARIES C. LlLE <br />DIRECTOR <br /> <br />DATE: <br />TO: <br />FROM: <br /> <br />June 25, 1997 <br />File <br /> <br />Tom Browning <br /> <br />RE: Weld County/Sheep Draw flood of June 13, 1997 <br /> <br />On June 24 Larry Lang and I performed field investigations in Weld County west of Greeley, A <br />significant rainstorm occurred on the evening of Friday, June 13 which caused flooding in the <br />Sheep Draw basin. As part of the field work, we conducted rainfall bucket surveys and estimated <br />peak discharges in Sheep Draw using indirect flow measurements, Following is a summary of <br />our findings : <br /> <br />STORM DESCRIPTION <br />. The storm developed on the evening of June 13 and generally moved from northwest to <br />southeast. <br />. Rainfall began in Weld County west of Greeley around 5 :00 pm, <br />. Most or all of the rain fell within a one hour time period. <br />. Hail was produced by this storm, but the amount and size of the hail was spatially quite <br />variable, <br /> <br />. RAINFALL ESTIMATES <br />Rainfall estimates were obtained through bucket surveys, interviews with local officials and <br />residents, and field observations, Rainfall estimates are shown (in inches) on the attached map, <br />These amounts are for the storm total (about 1 hour). <br /> <br />FLOOD DAMAGES <br />A flood damage survey was not performed by CWCB staff. However, flood damages were noted <br />during the field visit which included basement flooding in numerous homes, damage or <br />overtopping of several county road bridges, erosion/washout damage to several county roads, <br />damage to crops and fields, and significant debris accumulations. <br /> <br />RUNOFF ESTIMATE <br />A runoff estimate was obtained for Sheep Draw using indirect flow measurement techniques, A <br />channel cross-section was obtained by using a survey instrument, survey rod, and a 100' tape, <br />High water marks were excellent on both the left and right overbanks, A channel slope was <br />surveyed in the field, and "n" values were estimated for the overbanks and main channel. The <br />normal depth flow estimate is presented below: <br /> <br /> <br />Est. Peak flow <br />3,200 cfs <br /> <br />50. ear flow* <br />3.100 cfs <br /> <br />. * Based on hydrology values published in "Special Study, Cache La Poudre River Basin, <br />Larimer-Weld Counties, Colorado, Floodplain Analysis, Sheep Draw" (October 1981), <br />