Floods such as that in 1993 are unprecedented in modern history. The hydrologic enormity and severity of this particular flood are not subject to dispute. In all, 1,800 miles of rivers experienced record high flows, including 520 miles on the Mississippi, 415 miles on the Missouri, 190 miles on the Des Moines, 185 miles on the Kansas, 165 miles on the Iowa River, and shorter portions of eight other Midwestern rivers. Another 1,300 miles of rivers were listed as experiencing "major floods," those with flows rated above five-year return intervals but less than the record. These rivers and their major tributaries are shown in Figure 1-1.