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3889 MISSOURI RIVER BASIN 23 relatively short period of time and turns into flowing water the moisture that has been held back throughout tho. winter months in the form of snow and ice. This high-water periorj is usually accom~ panied by a relatively small amount of precipitation. It is charac- terized hy relatively sharp peaks, although tbe volume of water during this bigh-water period is considerable. Due to the fact that this rise is ordinarily accompanied by very little precipitation, tbc crest flattens as it continues downstream, and floods from this rise are usu~ ally most severe in the upper part of the river.' An example of a March rise flood is the one thllt occurred during the spring of 1943. This rise produced stages higher than uny since the 1881 flood from Pierre, S. Dak., to Rulo. Nebr. 18. The second general period of high water is often referred to as the June rise. This high-wt1ter period occurs subsequent to the March rise und is produced by the combine,l flm-off from t.wo sources: (1) tbe melting of snow from the mountains in the headwaters regions, which persists for u comparatively long period of time (2 or 3 months), and (2) run-off from rainfall occurring in the basin. Floods from tbis rise are ordinarily most severe in the lower part of tbe basin where the rainfall is normally the grcatest. The run-off from excessive snow melt from the heudwuters regions, comuined with run-off from beavy rainfall in the basin, produces floods of major proportions. Examples of tbis type of flood are tbosc whicb occurred in 1844 and 1903. 19. The Missouri River Vallcy is ulso subject to flush floods whicb occur at vurious times during tbe yeur. Maliy of tbese flash floods reacb major proportions for considerable distances along tbe river and usually occur us a result of heuVJ run-off from local tributuries or from local ice jams. Practically every year there is some flooding along the Missouri River from Sioux City to the mouth .s a result of flash floods. III. FLOOD fROBLEM 20. Agricultural area. IlUbject to tloods.-Between Sioux City, Iowa, and the mouth there are ahout 1,800,000 acres of land subject to flooding at extreme stages. Most of this fLrea is unde.f cultivation at the present time and includes some of tbe most fertile Illld productive land in the world. Tbe principal corps grown are COI'll, wheat, barley, rye, oats, alfalfa, and garden produce. Although the land is higbly productive, floods on the Missouri River have always constituted a serious hazard to fsrIning. Previous to the const,ruction of river improvement works, the land wus not only subject to floods but to " age by bank erosion and cut-offs. The threat from bank erosion 'cut-offs has now been removed by the river stabilization works, .ltlle flood hazard still remains. . , ,': 1\1unicipal area. sub.iect to tlo,Qd..-The principal cities subject to flooding ure the Kansas CitY'~h Kansas and Missouri; Council Bluffs, Iowa; Omaba, Nebr.; an !oux City, Iowa. , (a) The Kansas Citys, with total population of ove;.' a half ~ million p~ople, include in tbe bottom lunds subject to floods'il1)e stock- . yards WhlOh ar tbe second lurgest III the world, many manUfacturing , and industrial "'establishments, important rail lines and higl\,ways, t :wo airports, and the entire' Illunicipality of North Kansas City, Mo. i ,,~;~ ;'r"" " ,