Examining the relationship between flooding and large-scale climate indices over the central United States

Abstract:

This study examines the climatic driving forces responsible for the observed changes in flood frequency over the central United States (North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois, West Virginia, Kentucky, Ohio, Indiana, and Michigan). Results are based on daily streamflow records from 774 U.S. Geological Survey (USGS) stations with a record of at least 50 years and ending no earlier than 2011. Five climate indices related to both Atlantic and Pacific Oceans are used in this study: the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), and the Pacific-North American pattern (PNA). A peak-over-threshold approach is used to identify flood peaks, and the relationship between the frequency of flood events and climate drivers is investigated using Poisson regression. The results of this work indicate that changes in the climate system play a significant role in explaining the year-to-year variations in the frequency of flooding over the central United States. Different climate indices are related to the frequency of flood events over different parts of the domain and for different seasons. Analyses related to flood events are extended to examine climate controls on heavy rainfall over this area. The results indicate that the variability of the Atlantic and Pacific Oceans can influence the frequency of heavy rainfall days in a manner similar to what was found for flooding, both in terms of geographic regions and seasonality. Therefore, these results suggest that the recent observed changes in the frequency of flood events over the central United States can be largely attributed to changes in the climate system.