Understanding Flood Seasonality and its Temporal Shifts within the Contiguous United States

TitleUnderstanding Flood Seasonality and its Temporal Shifts within the Contiguous United States
Publication TypeJournal Article
Year of Publication2017
AuthorsYe, Sheng, Li Hong-Yi, L. Leung Ruby, Guo Jiali, Ran Qihua, Demissie Yonas, and Sivapalan Murugesu
JournalJournal of Hydrometeorology
Volume18
Number7
Pages1997-2009
Date Published07/2017
Abstract / Summary

Understanding the causes of flood seasonality is critical for better flood management. This study examines the seasonality of annual maximum floods (AMF) and its changes before and after 1980 at over 250 natural catchments across the contiguous United States. Using circular statistics to define a seasonality index, the analysis focuses on the variability of the flood occurrence date. Generally, catchments with more synchronized seasonal water and energy cycles largely inherit their seasonality of AMF from that of annual maximum rainfall (AMR). In contrast, the seasonality of AMF in catchments with loosely synchronized water and energy cycles are more influenced by high antecedent storage, which is responsible for the amplification of the seasonality of AMF over that of AMR. This understanding then effectively explains a statistically significant shift of flood seasonality detected in some catchments in the recent decades. Catchments where the antecedent soil water storage has increased since 1980 exhibit increasing flood seasonality while catchments that have experienced increases in storm rainfall before the floods have shifted toward floods occurring more variably across the seasons. In the eastern catchments, a concurrent widespread increase in event rainfall magnitude and reduced soil water storage have led to a more variable timing of floods. The findings of the role of antecedent storage and event rainfall on the flood seasonality provide useful insights for understanding future changes in flood seasonality as climate models projected changes in extreme precipitation and aridity over land.

URLhttps://doi.org/10.1175/JHM-D-16-0207.1
DOI10.1175/JHM-D-16-0207.1
Journal: Journal of Hydrometeorology
Year of Publication: 2017
Volume: 18
Number: 7
Pages: 1997-2009
Date Published: 07/2017

Understanding the causes of flood seasonality is critical for better flood management. This study examines the seasonality of annual maximum floods (AMF) and its changes before and after 1980 at over 250 natural catchments across the contiguous United States. Using circular statistics to define a seasonality index, the analysis focuses on the variability of the flood occurrence date. Generally, catchments with more synchronized seasonal water and energy cycles largely inherit their seasonality of AMF from that of annual maximum rainfall (AMR). In contrast, the seasonality of AMF in catchments with loosely synchronized water and energy cycles are more influenced by high antecedent storage, which is responsible for the amplification of the seasonality of AMF over that of AMR. This understanding then effectively explains a statistically significant shift of flood seasonality detected in some catchments in the recent decades. Catchments where the antecedent soil water storage has increased since 1980 exhibit increasing flood seasonality while catchments that have experienced increases in storm rainfall before the floods have shifted toward floods occurring more variably across the seasons. In the eastern catchments, a concurrent widespread increase in event rainfall magnitude and reduced soil water storage have led to a more variable timing of floods. The findings of the role of antecedent storage and event rainfall on the flood seasonality provide useful insights for understanding future changes in flood seasonality as climate models projected changes in extreme precipitation and aridity over land.

DOI: 10.1175/JHM-D-16-0207.1
Citation:
Ye, S, H Li, LR Leung, J Guo, Q Ran, Y Demissie, and M Sivapalan.  2017.  "Understanding Flood Seasonality and its Temporal Shifts within the Contiguous United States."  Journal of Hydrometeorology 18(7): 1997-2009.  https://doi.org/10.1175/JHM-D-16-0207.1.