Investigating the relationship between the frequency of flooding over the central United States and large-scale climate

The aim of this study is to examine whether the climatic driving forces can describe the observed variability in the frequency of flooding over the central United States. Results are based on daily streamflow records from 774 U.S. Geological Survey (USGS) stations with at least 50 years of data and ending no earlier than 2011. Five climate indices related to both the 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 indices is investigated using Poisson regression. The results of this work indicate that climate variability can play a significant role in explaining the variations in the frequency of flooding over the central United States. Different climate modes are related to the frequency of flood events over different parts of the domain and for different seasons, with PNA playing an overall dominant role. Analyses related to flood events are extended to examine climate controls on heavy precipitation over the same area. We find that the variability of the Atlantic and Pacific Oceans can influence the frequency of heavy precipitation days in a manner similar to what was found for flooding. Therefore, these results suggest that the recent observed variability in the frequency of flood events and heavy precipitation over the central United States can be largely attributed to the variability in the climate system.