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I I I I I I I I I I I I I I I I I 11 12 Hydrologic analyses were conducted using runoff computation~ based on existing land use and cover conditions in the watershed as of May 1973. Information regarding the type and location of existing and projected land uses were provided by the EI Paso County Planning Depart- ment. Comparison studies of present and future runoff showed insignifi- cant differences resulting from projected changes in land use. land treatment will not significantly affect the peak flow estimates for future flooding; however, a continuing land treatment program is necessary to curtail sediment and erosion damages. All technical data in thi s report are based on existing conditions. INTERPRETATION AND USE OF REPORT DATA I I I I I I I I I I I I I I I I I There are no streamflow records for Jimmy Camp Creek. Synthetic rainfall-runoff evaluation procedures were used in determining the flows for various frequency storms. These procedures are described in the SCS National Engineering Handbook, Section ~. Flood lines for the 100- and SOO-year floods were located on the aerial mosaics using the water surface elevations, cross-section data, and by interpolating between the cross-sections. Recognizing that aerial photographs are subject to displacement due to ground relief, the photographic image does not match the del ineated flood I ines in all areas. The location of flood lines at road crossings were computed using the normal openings of bridges and culverts. Because of the. multitude of possible events In which sediw~nt and debris could cause blockage of bridges and culverts, these considerations were not included in the study. In some locations, flooding occurs as shallow overland flow in transit from perched channels to the main channel. At these locations, the water surface elevations may not be level across the flood plain as in the normal situation. Technical Studies Maps The 10-, 2S-, SO-, 100- and SOO-year frequency flood events were analyzed and water surface profiles plotted showing elevations.at each cross-section. Water surface profile determinations were made using the U.S. Army Corps of.Engineers computer program HEC-2. The flood events have an average occurrence of once In the number of years as indicated. For example, the 100-year flood occurs once in 100 years on the average, and has a one percent chance of being equaled or exceeded in any given year.