New climate modeling predicts increasing occurrences of flash flooding
across most of the U.S.

Date:
April 26, 2022
Source:
University of Oklahoma
Summary:
A research team has created simulations from coupled climate and
hydrologic models that demonstrate widespread increases in the
occurrences of flash flooding events across most of the United
States.



FULL STORY ==========================================================================
The latest U.N. report on climate change documented researchers' efforts
that have shown some measures of global warming are now unavoidable,
and current research efforts are focusing on mitigation and adaptation strategies. The National Aeronautics and Space Administration describes
this as a global problem, felt on local scales. Likewise, National
Oceanic and Atmospheric Administration researchers are providing the
data, tools and information to better understand and prepare for climate change. One of the effects being impacted by the warming climate is a
change in frequency of flash flooding events, as well as the locations
in which they most often occur.


==========================================================================
A research team led by the University of Oklahoma, with the NOAA National Severe Storms Laboratory and collaborators at the National Center for Atmospheric Research, have created simulations from coupled climate and hydrologic models that demonstrate widespread increases in the occurrences
of flash flooding events across most of the United States.

The study is led by Yang Hong, a professor of hydrology and remote sensing
in the School of Civil Engineering and Environmental Sciences and in the
School of Meteorology at OU. He is the director of the Hydrometeorology
and Remote Sensing Laboratory and the founding director of the hydrology
and water security online master's program at OU. The research team's
findings are published in Nature: Communications Earth and Environment.Zhi
Li, a doctoral student with the HyDROS Lab, is the first author.

"This study builds upon the state-of-the-art model (EF5/CREST) that
is jointly developed by researchers with OU, NASA, and NOAA's National
Severe Storms Laboratory and has initiated collaboration with National
Center for Atmospheric Research climate scientists," said Li. "It realizes
the concept of 'Digital Twin in Earth System Science,' in which one is
our living climate and the other one is our future. Climate change never
became so real to me until we successfully collaborated on such research." "There hasn't been a real definitive study on what's going to happen
with flash floods in the future," said Jonathan J. Gourley, research hydrometeorologist with the NOAA National Severe Storms Laboratory and contributor to the study.

"We didn't have that robust of an observational record ... so, this study helped to fill in that gap. By using some of the rainfall simulations
from a convection-resolving climate model and then coupling with our high-resolution hydrologic modeling system, we can see what sort of
flash floods would be produced in the future." The research team
used climate simulations and modeling of a 30-year period, 2070-2100,
to predict the location and degree to which flash floods are likely to
occur. The effect, what the researchers call "flashiness," describes the likelihood of weather conditions that can cause rapid rainfall and lead
to flash flooding.



==========================================================================
They found that, if emissions continued at their current rate, flooding
events would become 7.9% "flashier" by the end of the century, meaning
heavy rainfall events are likely to occur quickly and in concentrated
areas that are likely to lead to flooding.

Similarly, their results show a more than 10% increase in flash flooding
in the Southwest U.S., the greatest increase in "flashiness" among
historical flash flood hot spots. The central U.S. is emerging as a new
flash flood hotspot as well, with an 8.6% predicted increase. Overall,
their results show future flash flood-prone regions are moving northwards.

"More people will have to learn not just how to survive floods but also
how to better live with ever-increasing flash floods," said Hong. "The
20-year return floods will more likely occur every two to five years, especially alarming for the emerging flashiness hotspots that will
be facing unprecedented challenges with aging infrastructure and
outdated flood risk measures. There is a pressing need to implement climate-resilient engineering infrastructure and develop smart
hydrological early warning systems." However, there is still time to
curb some of the more extreme impacts. Gourley says climate mitigation strategies could help.

"Now's the time to start thinking about better flood defenses," he
said. "Of course, decreasing greenhouse gas concentrations would be
the ultimate solution, but in the meantime, we can think about ways to
reduce vulnerabilities and improve flash flooding safety education."
"The majority of fatalities related to flash floods are not floods
finding people, but people finding floods, meaning they're out and about,"
he added.

"They're typically driving through a flooded roadway." The best way
to stay safe during flash flooding events is to stay off the roads and
avoid standing water.


========================================================================== Story Source: Materials provided by University_of_Oklahoma. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zhi Li, Shang Gao, Mengye Chen, Jonathan J. Gourley, Changhai Liu,
Andreas F. Prein, Yang Hong. The conterminous United States are
projected to become more prone to flash floods in a high-end
emissions scenario.

Communications Earth & Environment, 2022; 3 (1) DOI:
10.1038/s43247-022- 00409-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220426153650.htm

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