A Hydrometeorological Assessment of the Historic 2019 Flood of Nebraska, Iowa, and South Dakota

Authors

Paul Xavier Flanagan, University of Nebraska-LincolnFollow
Rezaul Mahmood, University of Nebraska-LincolnFollow
Natalie Umphlett, University of Nebraska-LincolnFollow
Erin M.K. Haacker, University of NebraskaFollow
Chittaranjan Ray, University of Nebraska-LincolnFollow
Bill Sorensen, University of Nebraska-LincolnFollow
Martha Shulski, University of Nebraska-LincolnFollow
Crystal J. Stiles, University of Nebraska - LincolnFollow
David Pearson, National Weather Service
Paul Fajman, National Weather Service

Date of this Version

6-2020

Document Type

Article

Citation

Bulletin of the American Meteorological Society, June 2020, E817-E829

DOI 10.1175/BAMS-D-19-0101.1.

Comments

US government work

Abstract

During early 2019, a series of events set the stage for devastating floods in eastern Nebraska, western Iowa, and southeastern South Dakota. When the floodwaters hit, dams and levees failed, cutting off towns, while destroying roads, bridges, and rail lines, further exacerbating the crisis. Lives were lost and thousands of cattle were stranded. Estimates indicate that the cost of the flooding has topped $3 billion as of August 2019, with this number expected to rise.

After a warm and wet start to winter, eastern Nebraska, western Iowa, and southeastern South Dakota endured anomalously low temperatures and record-breaking snowfall. By March 2019, rivers were frozen, frost depths were 60-90 cm, and the water equivalent of the snowpack was 30-100 mm. With these conditions in place, a record breaking surface cyclone rapidly developed in Colorado and propagated eastward, producing heavy rain towards the east and blizzard conditions toward the west. In areas of eastern Nebraska, western Iowa, and southeastern South Dakota, rapid melting of the snowpack due to this rain-on-snow event quickly led to excessive runoff that overwhelmed rivers and streams. These conditions brought the region to a standstill.

In this paper, we will provide an analysis of the antecedent conditions in eastern Nebraska, western Iowa and southeastern South Dakota, the development of the surface cyclone that triggered the historic flooding, along with a look into the forecast and communication of flood impacts prior to the flood. The study used multiple datasets, including in-situ observations and reanalysis data. Understanding the events that led to the flooding could aid in future forecasting efforts.