Major floods on the Kansas River are usually caused by a series of short-duration, high-intensity storms following a protracted period of general rains which reduce the infiltration capacity of the soil to a minimum and cause a greater than normal flow in the stream channels. Many of the early floods in the Kansas River Basin are a matter of legend and tradition rather than actual historical record. Early floods affecting the area in the vicinity of Manhattan occurred in 1785, 1826, 1844, 1845, 1851, 1858, 1870, 1881, and 1886, but very little is known concerning these floods (USACE 1959). More recent flood events for which records are available occurred in 1903, 1904, 1908, 1915, 1935, 1941, 1945, 1947, 1948, 1950, 1951, and 1993. The 1844 flood appears to have produced the maximum stages of record on the Kansas River followed in magnitude by the 1951, 1903, and 1993 stages.
Flood of 1844
A great flood is known to have occurred on the Kansas River in June 1844. Data are not available on the nature, extent, and magnitude of the storm rainfall, and only fragmentary data on flood stages are available. A stage of about 40 feet occurred on the Kansas River at Manhattan.
Flood of 1903
The second largest flood for which reliable stage records are available occurred during the latter part of May and the first part of June 1903. This flood resulted from extraordinarily heavy rainfall the last five days in May preceded by above-normal rainfall throughout May. The rainfall at Abilene was estimated at 15 inches on May 28. Flood stage was exceeded approximately 16 days at Manhattan.
Flood of 1951
The maximum flood of record occurred in July 1951 and resulted from the combined effects of well above average rainfall in May and June 1951 and a major event spanning four days (July 9 through 12) of extremely heavy precipitation over the lower portion of the Kansas River Basin. About 40 percent of Kansas received more than 10 inches of rain during June 1951. This area included most of the Smokey Hill River Basin and portions of the Republican River Basin. The Big Blue River basin north to the Nebraska border had rainfall in excess of 12 inches, with one area exceeding 14 inches.
The Kansas River at Manhattan was above flood stage (17 feet) on June 4, June 7 through 19, and June 22 through July 24, 1951 for a total of 47 days. The maximum gage height of 33.40 feet occurred at 3:00 a.m., July 13, with an estimated discharge of 300,000 cfs in the Kansas River and about 98,000 cfs in the Big Blue River. The USACE reported peak discharge for the Big Blue River near Manhattan in the 1959 report varies approximately 4600 cfs from the USGS peak discharge of 93,400 cfs recorded for the Big Blue River near Manhattan Gage in the 1951 flood.
Flood of 1993
The third largest flood for which reliable stage records are available occurred in July 1993. Moderate to major flooding occurred on the Kansas, Big Blue, Black Vermillion, Smoky Hill, Solomon, Saline, and Republican Rivers and their tributaries. As with the flood of 1951, heavy rainstorms in July were preceded by several months of above average rainfall. Manhattan received more than 100 percent of the normal precipitation (1961 to 1990 average) for January through June 1993. May through July precipitation at Manhattan was 35.38 inches and was the second wettest period in 104 years of record. July rainfall was 535 percent of the normal.
A comparison of observed controlled and simulated uncontrolled daily mean discharge in the Blue River near Manhattan for July 1993 indicated that the storage of floodwaters in Tuttle Creek Lake reduced a potentially devastating flood of more than 95,000 cfs on July 5 on the Big Blue River near Manhattan to a much less destructive flood of 60,000 cfs on July 25. The water surface elevation in the Big Blue came within 3 to 4 feet of the top of the Big Blue River section of the Manhattan Kansas levee. Without the reservoir storage, the Big Blue River near Manhattan would have overtopped the Federal levee, and flooding downstream along the Kansas River would have been much more severe. High stages on the Big Bluer River were most noticeable upstream and near the U.S. Hwy 24 and Union Pacific bridge crossings. The Manhattan levee did not fail, but this incident prompted great concern about the levee under potential higher flow conditions.