Flooding in the southern Midwestern United States, April–May 2017

Excessive rainfall resulted in flooding on numerous rivers throughout the southern Midwestern United States (southern Midwest) in late April and early May of 2017. The heaviest rainfall, between April 28 and 30, resulted in extensive flooding from eastern Oklahoma to southern Indiana including parts of Missouri, Arkansas, and Illinois.

Peak-of-record streamflows were set at 21 U.S. Geological Survey (USGS) streamgages in the southern Midwest during the resulting April–May 2017 flooding and each of the five States included in the study area had at least one streamgage with a peak of record during the flood. The annual exceedance probability (AEP) estimates for the April–May 2017 peak streamflows indicate that peaks at 5 USGS streamgages had AEPs of 0.2 percent or less (500-year recurrence interval or greater), and peak streamflows at 15 USGS streamgages had AEPs in the range from greater than 0.2 to 1 percent (500- to 100-year recurrence intervals).

Examination of the magnitude of the temporal changes in median annual peak streamflows indicated positive increases, in general, throughout the study area for each of the 1930–2017, 1956–2017, 1975–2017, and 1989–2017 analysis periods. The median increase in peak streamflows was greatest in 1975–2017 and 1989–2017 with maximum increases of 8 to 10 percent per year. No stations in the 1975–2017 or 1989–2017 analysis period had median negative changes in peak streamflows.