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<br />2.3 Pri nci pal Flood probl ems <br /> <br />Floods on the Arkansas River are of two general types. One type is <br />represented by "spring floods" which result frOOl melting snow and <br />can often be augmented by ra i nfa 11 runoff. The other type is <br />represented by "sunmer floods" which result entirely frOOl rainfall. <br />The spring fl oods are characterized by cOOlparatively moderate rates <br />of flow of long duration with large volumes of runoff. The summer <br />floods are characterized by high peak rates of discharge with <br />relatively smaller volumes of runoff. <br /> <br />Detailed information on floods before the turn of the century is <br />very limited. Information on past flooding is based on newspaper <br />accounts and interviews with longtime residents of the area. Large <br />floods occurred at La Junta in 1886, 1921, 1955, and 1969. These <br />floods have caused major damage, disrupting highway, railroad <br />traffic and cOTl11lunication services, drowned 1 ivestock, destroyed <br />agricultural lands, roads, bridges and buildings. Several persons <br />have lost their lives and others have been injured. <br /> <br />The flood of June, 1921, is considered the most severe flood known <br />to occur in La Junta. The river reached a discharge of 200,000 <br />cubi c feet per second (Reference 3). The fl ood wa s tri ggered by <br />two areas of intense rainfall above Pueblo. One of these was north <br />of the towns of Florence and Canon Ci ty and the other wa s fa i rl y <br />well distributed over the Arkansas River watershed. Precipitation <br />was reported to have been as much as 11 inches in six hours whil e <br />in the other area it was reported to have been as much as nine <br />inches in six hours. The rainfall in the upper area was reported <br />to have occurred first so that runoff combined with that below to <br />produce the largest flood of record. Above La Junta the effect of <br />valley storage on peak attrition was obscured by the inflow from <br />tributary streams. North La Junta was flooded; water was 4 to 6 <br />feet deep on Second Street and reached the Otero County Ja il . It <br />was reported that 13 persons were drowned al though some of the <br />bodies were not found until June 9. Areas along the Huerfano and <br />Purgatoire Rivers and Timpas, Adobe, and Horse Creek were flooded. <br />Heavy rains occurred on the main stem of the Arkansas River frOOl La <br />Junta to Lamar. Below La Junta tributary inflow was small. <br /> <br />2.4 Flood Protection Measures <br /> <br />The City of La Junta has purchased all of the acreage in the flood <br />plain along the King Arroyo and is currently excavating this area <br />and building a dike. This area will be used for a park or open <br />space. The city has al so adopted the flood plain management <br />regulations written by FEMA. <br /> <br />3.0 ENGINEERING METHODS <br /> <br />The flood plains in La Junta were estimated using standard hydrologic and <br />hydraulic study methods to determine the flood hazard data required for <br />this study. Flood events of the magnitude which are expected to be <br /> <br />6 <br />