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<br />. <br /> <br />(/ <br /> <br />~ <br /> <br />~ <br /> <br />( <br /> <br />~ <br /> <br />( <br /> <br />r <br /> <br />. <br /> <br />- 26 - <br /> <br />The results of the investigations and analyses were presented <br />to the sponsors for final acceptance. A watershed-wide meeting was <br />held by the sponsors .for review of the final watershed plan. It <br />was determined. that the proposed project meets the objectives of <br />the sponsors. <br /> <br />Hydraulic and Hydrologic Investigations <br /> <br />Hydrologic investigations were related to the probability of <br />various flood magnitudes and to the location and area of resulting <br />damage. This relationship supported the economic justification of the <br />recommended plan. Approved standard Service criteria and methods were <br />used on hydrologic development. <br /> <br />Flood-producing storms in the Indian Wash area are characterized <br />by local, high intensity, short duration storms that increase in <br />intensity along the Little Book Cliffs. The hydrologic studies and <br />flood damage evaluation for Indian Wash were based on the above <br />characteristic storms having increasing rainfall depths with increasing <br />elevation. This resulted in a design storm for floodwater-retarding <br />storage ranging from 3.2 inches depth in the lower portion of the water- <br />shed, near Grand Junction, up to 4.6 inches at the upper extremity <br />of the watershed, along the face of the Little Book Cliffs. It <br />produced a weighted storm depth of 4.1 inches resulting in 3 inches <br />of runoff to storage. . <br /> <br />. <br /> <br />Rates of discharge, on Which economic evaluation was determined, <br />were based on this distribution of storm, according to elevation. <br /> <br />A rainfall record of 67 years was available for the Grand <br />Junction station at the time of study. This__record of rainfall was <br />related to frequency and converted into six-hour amounts. <br /> <br />The result of this study is as follows: <br /> <br />Precipitation <br />6-Hr. Amounts <br /> <br />Frequency <br /> <br />lOO-year <br />50-year <br />25-year <br />la-year <br />5-year <br /> <br />2.4 inches <br />1.8 inches <br />1.5 inches <br />1.1 inches <br />0.8 inch <br /> <br />There are no streamflow records for the Indian Wash Watershed. <br />The floodplain common to Indian Wash and the Colorado River is not <br />classed as a damage area in this study. <br /> <br />. <br />