The 1993 Midwest Extreme Precipitation in Historical and Probabilistic Perspective

Abstract

Extreme rainfall amounts that resulted in severe flooding during the spring and summer of 1993 along the Missouri and Mississippi Rivers are examined from a historical and probabilistic viewpoint. Long-term average precipitation amounts and the departures of the 1993 summer rainfall from these averages are presented. Also, climatic regionalization and precipitation probabilities developed for the National Drought Atlas using L-moment techniques have been applied to the drainage area that contributed to the flooding. The exceedance probabilities of monthly and multiple-month observed precipitation amounts have been calculated. The results show that the three-month period May-July experienced unusually heavy rainfall when compared to prior years, and that July was particularly wet. Recurrence intervals for the rainfall events vary widely depending on the specific time period and locality, but the observed precipitation was an extreme event.