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Impacts of Hurricane Winds and Precipitation on Hydrodynamics in a Back‐Barrier Estuary

DOI:10.1029/2020JC016483
Authors:
Alexander Rey at Queen's University
Alexander Rey
D. Reide Corbett at East Carolina University
D. Reide Corbett
Ryan P. Mulligan at Queen's University
Ryan P. Mulligan
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Abstract and Figures

During extreme storms, both wind‐driven changes in water levels and intense precipitation can contribute to flooding. Particularly on low‐lying coastal plains, storm‐driven flooding can cover large areas, resulting in major damage. To investigate the roles of rainfall and storm surge on coastal flooding, a coupled flow‐wave model (Delft3D‐SWAN) that includes precipitation is used to simulate two major storm events. The modeling system is applied over a domain covering coastal North Carolina, USA, including the large Albemarle‐Pamlico estuarine system, and a long and narrow back‐barrier estuary (Currituck Sound [CS]) that experiences major water level variations is investigated in detail. A high‐resolution (50 m) grid with eight vertical layers is used to simulate the conditions during Tropical Storm Hermine and Hurricane Matthew in 2016. Hindcasts (winds, pressure, and precipitation) from eight different atmospheric models are used as atmospheric input conditions, and the results are compared with detailed observations of surface waves, currents, and water levels from sensors mounted on five monitoring platforms in CS. Results show that major differences exist between wind fields producing variations coastal conditions. Precipitation directly on the water surface had a large effect on water levels and produced a larger inundated area. These results help to understand the important contributions of each physical process (precipitation, wind‐driven surge, and waves) to circulation and water levels, and provide guidance on the impact of atmospheric forcing conditions on back‐barrier environments during hurricanes.
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1. Introduction
Tropical cyclones, also known as hurricanes, are intense weather events which present a significant and
increasing natural hazard in coastal areas (Elko etal.,2019; Field et al.,2014; Knutson et al.,2010; Riss-
er & Wehner,2017; Wahl etal., 2015). Already the most destructive natural disaster in the United States
(Grinsted etal.,2019), these storms are projected to increase in intensity (Wahl etal.,2015), precipitation
(Villarini etal.,2011), and frequency with future climate warming (Knutson etal.,2010). During tropical
cyclones strong winds can produce storm surge, generate large waves, and drive strong currents, resulting in
a multihazard coastal environment. Improving the understanding of how these processes interact to drive
hydrodynamics in estuaries and cause coastal flooding is a vital research area (Chaumillon etal.,2017; Clu-
nies etal.,2017; Elko etal.,2019). This hazard has been highlighted by flooding events during several recent
hurricanes along US coasts, including Hurricane Katrina in 2005 (Fritz etal., 2007), Hurricane Irene in
2011 (Mulligan etal.,2015b), and Hurricane Sandy in 2012 (Bennett etal.,2018; Beudin etal.,2017). These
storms can deliver large amounts of precipitation over short periods, which combined with wind-driven
Abstract During extreme storms, both wind-driven changes in water levels and intense precipitation
can contribute to flooding. Particularly on low-lying coastal plains, storm-driven flooding can cover large
areas, resulting in major damage. To investigate the roles of rainfall and storm surge on coastal flooding,
a coupled flow-wave model (Delft3D-SWAN) that includes precipitation is used to simulate two major
storm events. The modeling system is applied over a domain covering coastal North Carolina, USA,
including the large Albemarle-Pamlico estuarine system, and a long and narrow back-barrier estuary
(Currituck Sound [CS]) that experiences major water level variations is investigated in detail. A high-
resolution (50m) grid with eight vertical layers is used to simulate the conditions during Tropical Storm
Hermine and Hurricane Matthew in 2016. Hindcasts (winds, pressure, and precipitation) from eight
different atmospheric models are used as atmospheric input conditions, and the results are compared
with detailed observations of surface waves, currents, and water levels from sensors mounted on five
monitoring platforms in CS. Results show that major differences exist between wind fields producing
variations coastal conditions. Precipitation directly on the water surface had a large effect on water levels
and produced a larger inundated area. These results help to understand the important contributions of
each physical process (precipitation, wind-driven surge, and waves) to circulation and water levels, and
provide guidance on the impact of atmospheric forcing conditions on back-barrier environments during
hurricanes.
Plain Language Summary Winds and heavy rain can result in coastal flooding during
extreme storms, such as hurricanes. This is a major hazard in coastal areas, where flooding from storms
can cover large areas and produce substantial damage. To help understand the forces that contribute
to this hazard, a model is applied to simulate the waves, water levels, and currents in Currituck Sound
(CS), part of the larger Albemarle-Pamlico estuarine system in coastal North Carolina, USA. Two major
storms are simulated, Tropical Storm Hermine and Hurricane Matthew in September and October 2016.
Observations were collected from five monitoring platforms in CS, and the measurements indicate that
large changes in water levels occurred during both storms. Winds, pressure, and precipitation are used as
model inputs, and the simulation results are compared with observations of surface waves, currents, and
water levels. The results help to understand the roles of precipitation, wind, and waves on the motion of
water in back-barrier estuaries and coastal flooding during tropical storms.
REY ET AL.
© 2020. American Geophysical Union.
All Rights Reserved.
Impacts of Hurricane Winds and Precipitation on
Hydrodynamics in a Back-Barrier Estuary
Alexander J. M. Rey1 , D. Reide Corbett2 , and Ryan P. Mulligan1
1Department of Civil Engineering, Queen's University, Kingston, ON, Canada, 2Integrated Coastal Programs, East
Carolina University, Greenville, NC, USA
Key Points:
• Surface waves and coastal
hydrodynamic were simulated in a
long and narrow estuary during two
tropical storms
• After comparing atmospheric
inputs, model results were in general
agreement with observations from
five monitoring platforms using
Rapid Refresh winds
• Results indicate that both wind-
driven storm surge and precipitation
directly on the water surface
contribute to flooding
Supporting Information:
• Supporting Information S1
Correspondence to:
R. P. Mulligan,
ryan.mulligan@queensu.ca
Citation:
Rey, A., Corbett, D. R., & Mulligan, R.
P. (2020). Impacts of hurricane winds
and precipitation on hydrodynamics
in a back-barrier estuary. Journal
of Geophysical Research: Oceans,
125, e2020JC016483. https://doi.
org/10.1029/2020JC016483
Received 5 JUN 2020
Accepted 30 SEP 2020
10.1029/2020JC016483
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