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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />6 <br /> <br />and have poor internal drainage. Available water holding capacity is low in <br />the subsoil. Because the surface layer has slow permeability, runoff is <br />enhanced. Natural fertility is low to moderate, but these soils are subject <br />to soil blowing unless they are protected by growing crops or crop residue. <br />These soils are classified as a "0" soil type, as defined in the SCS <br />hydrologic methodology, runoff and curve number values range from CN 80 to 89. <br />The vegetative cover of the major drainage basins is classified as rangeland <br />in moderate to poor condition. Irrigated land is also prevalent in the lower <br />portions of the major drainage basins. These irrigated lands primarily con- <br />sist of row-type crops under good irrigation and cultivation practices. <br />Figure 2 is a generalized map of the soils within the study area. <br /> <br />Land Use <br />Figure 3 presents the land uses used in the hydrologic modeling. Land <br />uses were obtained from the most current Town of Ordway Zoning Map. Several <br />various types of land uses were identified, including single-family residen- <br />tial, multi-family residential, commercial, and industrial uses. Proposed <br />1 and development projects which were considered when evaluating the runoff <br />characteristics of the area are summarized on Table 1. <br /> <br />Rainfall <br />Rainfall data lias obtained from the "Precipitation - Frequency Atlas of <br />the Western United States, Volume III - Colorado", published by the National <br />Oceanic and Atmospheric Admi nistration, in 1973. Peak discharges for the 5-, <br />10-, 50-, and 100-year flows under existing drainage basin conditions were <br />predicted using rainfall depth of the 2- and 6-hour duratian storms specific <br />ta the Ordway area. Rainfall/depth distributians are summarized in Table 2. <br />The duration of a storm reflects the type of starm and is significant <br />depending an the size .of the drainage basin. The short duratian starm pat- <br />terns of 6 hours and less typically cause flaads in smaller drainage basins, <br />generally 10 square miles and below. An example .of a short duratian storm is <br />a highly lacal ized cloud burst event, which causes floading because of the <br />almast instantaneaus runoff. Longer duratian storms, 6 haurs and greater, are <br />