November 16, 2021

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Tropical Cyclones Affect Mid-Atlantic Flood and Drought Variability

A climatological analysis shows the hydrological extremes caused by tropical cyclones from 1950‒2019 over the Mid-Atlantic region.

Research using long-term, distributed observational datasets shows substantial regional variations in tropical cyclone impacts on floods and droughts in the Mid-Atlantic.

[Courtesy Henk Sijgers | Flickr ]

The Science

Researchers lack knowledge about the climatological characteristics of landfalling tropical cyclones (TCs) and their local-scale hydrological impacts over the Mid-Atlantic region. Through analyzing long-term observational datasets, this research found strong spatial variability in how TCs affect floods and droughts within the region. For instance, while TCs appear to have negligible impacts on flooding in the northern part of the region, they increase the magnitude of 100-year floods by over 50% for the southwestern portion. However, to varying degrees, TCs can alleviate hydrological droughts (in frequency and duration) for most of the region.

The Impact

Landfalling TCs are major drivers of catastrophic flood hazards in the Mid-Atlantic region, where reducing flood risk and damage involves crucial coastal management decisions. However, existing research exploring TC-related hydrological extremes focuses mostly on regional scales, which are too coarse for realistic decision-making, which often occurs at local or catchment scales. Through analysis of extreme events based on long-term, spatially distributed observational datasets, this research reveals substantial spatial variability in TC impacts on the severity of floods and droughts. The results of this research highlight the need to prioritize sites for coastal hazard risk management and adaptation. They also demonstrate the importance of high-resolution modeling for characterizing spatial heterogeneity in processes and system responses.


Researchers performed a climatological analysis of long-term (from 1950‒2019), spatially distributed observational datasets of hurricane tracks, precipitation, and streamflow. The analysis provided local scale understanding of the climatological characteristics and hydrological impacts of TCs over the Mid-Atlantic region, defined as the Delaware River Basin (DRB) and Susquehanna River Basin (SRB). Although TCs make limited contributions to regional precipitation (<9%), they are the major trigger of most extreme floods in the southern part of DRB (tributaries of the Christina River and lower Delaware River) and the southwestern portions of SRB (tributaries of the Lower Susquehanna and Junita River). TCs also alleviate droughts in these areas to a comparatively higher degree. Importantly, researchers observed a strong spatial variability of TC’s impact on floods and droughts within and across the basins. For instance, while the TC effect on flood is negligible for the high-elevation, northern part of the region, TCs increase the magnitude of the 100-year flood by up to 19.6% in DRB and 53.0% in SRB. TCs also reduce the duration of short-term extreme hydrological drought by up to 25.0% in SRB and 24.7% in DRB, respectively.

Principal Investigator

Robert Hetland
Pacific Northwest National Laboratory
[email protected]

Co-Principal Investigator

Ning Sun
Pacific Northwest National Laboratory
[email protected]

Program Manager

Jennifer Arrigo
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]


This work is part of the multiprogram, collaborative Integrated Coastal Modeling (ICoM) project. It was supported by the MultiSector Dynamics (MSD), Earth System Model Development (ESMD), and Regional and Global Modeling and Analysis (RGMA) program areas of the Biological and Environmental Research (BER) Program within the Department of Energy’s (DOE) Office of Science. All model simulations were performed using resources available through Research Computing at Pacific Northwest National Laboratory (PNNL).


Sun, N., et al. "Climatological Analysis of Tropical Cyclone Impacts on Hydrological Extremes in the Mid-Atlantic Region of the United States." Environmental Research Letters 16 (12), 124009  (2021).