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<br />- 7 - <br /> <br />- 8 . <br /> <br />. <br /> <br />May 1894. At that time there was a very minor amount of development in <br /> <br /> <br />the watershed, and no records of monetary damage have been located. <br /> <br />for future flooding; however, a continuing land treatment program is <br /> <br /> <br />necessary to curtail sediment and erosion damages. All technical data <br /> <br /> <br />in this report are based on existing conditions. <br /> <br />SOURCES OF DATA AND TECHNICAL STUDIES <br /> <br />Maps <br /> <br />The 100-year frequency flood event was analyzed and water surface <br /> <br /> <br />profiles plotted showing elevations at each cross.section. The 100-year <br /> <br /> <br />flood has a one percent chance of being equaled or exceeded in anyone <br /> <br /> <br />year and occurs on the average once in 100 years. <br /> <br />. <br /> <br />Base maps were developed from U. S. Geological Survey topographic <br /> <br /> <br />maps (scale 1:24,000). Flood hazard areas are plotted on topographic <br /> <br /> <br />maps prepared especially for this study. The low level aerial photo. <br /> <br /> <br />graphy was provided by Fremont County and was flown in June 1975. <br /> <br /> <br />Detailed topographic mapping was produced photogrammetrically from the <br /> <br /> <br />aerial photography. The maps were reproduced on a scale of I" = 200' <br /> <br /> <br />with a 2-foot contour interval. Map topography complies with national <br /> <br /> <br />map accuracy requirements. Topographic data was used to compute water <br /> <br /> <br />surface profiles and the flood hazard area outlines. <br /> <br />Flood lines for the 100.year flood were located on the topographic <br />maps using the water surface elevations, cross.sectlon data, and by <br />interpolating between the cross.sections. Cross-section information was <br /> <br />taken directly from the topographic maps. <br /> <br />INTERPRETATIONS AND RECOMMENDATIONS <br /> <br />Interpretations <br /> <br />Technical Studies <br /> <br />There are no streamflow records for Red Canyon Draw. Synthetic <br /> <br /> <br />rainfall-runoff evaluation procedures developed by the Soil Conservation <br /> <br /> <br />Service were used in determining the flows for the 100-year frequency <br /> <br /> <br />storm. <br /> <br />The need for adequate storm drains to carry the flows of Red Canyon <br />Draw and runoff from contributing areas has been recognized by city and <br />county planners. Subdividers, and developers are required to submit <br />proposed drainage plans to the county planning commission for approval. <br />In the past, drainage plans have been prepared singularly or on a plat- <br />by-plat basis. locations of potential flooding by the IOO-year frequency <br />storm on Red Canyon Draw and its tributaries was not known until this <br /> <br />. <br /> <br />Hydrologic analyses were conducted using runoff computations based <br /> <br /> <br />on existing land use and cover conditions in the watershed as of June <br /> <br /> <br />i975. land treatment will not significantly affect the peak flow estimates <br />