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<br />." <br />~~ <br /> <br /> <br />Land use within sub-basins SW I, SW II, SW III, and SW <br />IV is predominantly devoted to dry land wheat farming. With <br />the exception of the Town of Otis itself, land use within <br />sub-basin S is exclusively native grass pasture. <br /> <br />2.3 Unnamed Tributary <br /> <br />The majority of the northern, unnamed basin lies <br />between the railroad and Surveyor Creek. The thalweg of the <br />northern basin passes parallel to and approximately 1300 <br />feet north of the northern town limits. 'The northern <br />thalweg's closest approach to the corporate limits is at the <br />northwest corner of Otis near the airstrip. This basin will <br />be referred to throughout the remainder of this report as <br />the northwest basin. The northwest basin is divided into <br />three sub-basins identified as NW I, NW II, and NW III on <br />the basin map. <br /> <br />Land use within this tributary is, with the exception <br />of a portion of Otis, devoted predominantly to dry land <br />wheat farming. <br /> <br />2.4 Hydrologic Analysis <br /> <br />2.4.1 Flood Characteristics <br /> <br />Flooding in Otis would typically result from <br />general rainstorms and cloudburst storms in the months <br />of May through September. Flood hydrographs resulting <br />from heavy general rainfall over the basin would be <br />characterized by high peak flow of moderate volume and <br />duration. Flood hydrographs resulting from cloudburst <br />type storms would be characterized by high peak flow of <br />short duration and a small volume of runoff. <br /> <br />2.4.2 Hydrology <br /> <br />A hydrologic analysis was conducted to determine <br />runoff hydrographs from two-hour rainfall depths for <br />the 10- and 100-year recurrence intervals. (A <br />hydrograph describes the instantaneous discharge from a <br />basin as a function of time.) A rainfall depth of a <br />given return period was assumed to generate a flood <br />hydrograph of the same return period. Flood flows and <br /> <br />4 <br />