In October 2015, devastating flooding across South Carolina over five days killed 19 people and caused an estimated $1.5
billion in damages. In addition, nearly 50 dams failed or were breached.
Eight years later in September 2023, unprecedented rainfall from Storm Daniel over
the Wadi Derna watershed caused an extreme flooding event that hit the North African
coastal city of Derna, Libya. And last July, the Guadalupe River in Texas surged nearly
30 feet as more than 100 people were killed, including 27 children and counselors
at Camp Mystic.
A 2022 World Bank study estimated that 1.81 billion people are directly exposed to a 1-in-100-year flooding
event. While extreme flooding cannot be prevented, Civil and Environmental Engineering Professor Jasim Imran’s team are studying causes and effects and developing prediction
solutions for helping with improved early warning and evacuation strategies.
“Patterns have changed,” Imran says. “They’re not like before, so we need to be proactive with our infrastructure,
our resources, and our understanding of the process. We need to be resilient to whatever
comes our way.”
Last year, Imran’s team completed a study of the Texas floods, and graduate student
Ayman Nemnem presented the findings at last month’s American Geophysical Union Conference. The findings included how two $300 sensors, built by the Adaptive Real-Time
Systems Laboratory led by Mechanical Engineering Associate Professor Austin Downey, placed in the right location could have provided early warning signals and saved
lives.
“By developing a model, we identified locations where the sensors could detect the
rate at which the water was rising,” Imran says. “This would have provided four-to-five
hours of lead time to evacuate the camp.”
Imran’s team also investigated catastrophic flooding in Libya, which claimed more
than 10,000 lives. Their article, “How extreme rainfall and failing dams unleashed the Derna flood disaster,” which was published last May in Nature Communications, has been accessed more than 12,000 times with nine citations. The study has also
been referenced by major international outlets, including The Washington Post and the United Nations Office for Disaster Risk Reduction.
The disaster was reconstructed using an integrated modeling approach that combined
satellite imagery, simulations, machine learning, eyewitness accounts and digital
elevation data to assess the impact of cascading dam failures. While the dams were
in disrepair, the findings revealed that even if they were structurally sound, they
would have only provided minimal protection against the extreme runoff.
The collapse of aging flood control infrastructures, compounded by inadequate risk
assessment and emergency preparedness, escalated the disaster’s impact. Their findings
underscored the urgent need for systematic dam safety evaluations, enhanced flood
forecasting, and adaptive risk management strategies.
“The high number of casualties were only possible due to a dam failure,” Imran says.
“We wanted to look more into what happened and if there was any data we could extract
since there was not much to create a model.”
Imran’s team performed investigative work to obtain data, which included news reports
and literature. Since acquiring rainfall data was challenging, they examined satellite
data and compared it with a rain gauge that was near the affected area, allowing them
to reproduce the event.
“Our main finding was that there would have been significant flooding and some casualties
without any dams, but not at the scale of what happened,” Imran says. “The dams were
not holding any water and since the rain fell in a short amount of time, it filled
the wells over the top, causing a collapse.”
Imran’s interest in extreme flooding began with the devastating floods in South Carolina
in October 2015. Imran’s team has published three articles on that event, including
his most recent article in Water Resources Research this past November.
“We published the first article in the Journal of Hydraulic Engineering in 2017 after
students working with Dr. [Hanif] Chaudhry and me conducted field sampling and analysis,”
Imran says. “In a more recent study published in National Hazards Review, simulations led by Ayman showed that pre-storm pumping from some lakes could have
reduced stress on downstream dams.”
According to Imran, dams that were constructed within the last 50 years were designed
to withstand extreme storms. But a solid infrastructure is not effective without regular
monitoring and maintenance. For example, if a small earthen dam is not maintained,
animals can create a burrow and allow water to escape and cause a failure.
“I think South Carolina is working to make dams more regulated,” Imran says. “There
are thousands of dams in the state, but the smaller ones are hard to manage and regulate
because many of them are private and have different owners over time.”
Nemnem says that he is motivated in his work by knowing that he can help protect people
from the devastation of extreme flooding. In addition, many of the processes that
he studies as part of Imran’s team are not location specific and can be applied to
dams and watersheds worldwide.
“We can improve preparedness through better forecasting, early warning and practical
mitigation tools. Helping communities act sooner to reduce loss of life makes this
work deeply satisfying,” Nemnem says. “Examining how failures at one dam can trigger
downstream dam failures in South Carolina and Libya reinforced how transferable and
urgently needed this research is for improving dam safety and emergency planning globally.”
