Both Natural and Man-Made Barriers Can Help Slow Hurricane Surges
Hurricanes are fearsome storms with their high winds, tornadoes—and deadly waters. Storm surge is historically “the leading cause of hurricane-related deaths in the United States,” the Federal Emergency Management Agency says.
However, despite the real risks of catastrophic hurricanes coming ashore, tens of millions of people live, work, fish, and play close to US coastlines. What—if anything—can governments and communities do to strengthen the safety of their coasts against these monster storms?
The answer is that there is a great deal that can be done to blunt at least some of the power of hurricanes, but it requires learning from past storms, investments in coastal safety, and public-private cooperation to decide which strategy to use.
Mighty Gulf Storms
Hurricanes Helene and Milton recently made landfall in the USA after sustaining top wind speeds of 180 mph (290 km/h) and 140 mph (225 km/h), respectively, while still offshore in the Gulf of Mexico. Such winds generated the surface waves and storm surge that devastated coastal communities. [See The Earth & I article “First Comes the Disaster, Then Comes the Debris.”]
Not only did Category 4 Hurricane Helene impact Florida’s coasts—moving north from Tampa, past low-lying Cedar Key, and into Florida’s Big Bend region on September 26, 2024—it also affected communities further inland in Florida, Georgia, South Carolina, North Carolina, and Tennessee with wind and precipitation and resultant tornadoes (see Figure 1).
“In general, the stronger a storm [is], and the longer it stays over an area, the more rainfall we will get; and so, flooding/storm surge and wind gusts will all contribute to the destructive power,” explains Chanh Kieu, associate professor in earth and atmospheric sciences at Indiana University Bloomington.
The storm surge for Hurricane Helene was estimated at an extraordinary 15 feet (~4.5 m). Hurricane Milton, which hit central west Florida as a Category 3 storm on October 10, 2024, had approximately 10 feet (~3 m) in storm surge.
Government leaders, coastal communities, and state inhabitants took all the precautions they could to survive the storms.
These preparations could be helped with advance analysis of two things: Knowing ahead of time how high the storm surge will be could greatly improve communities' ability to prepare and inform the public to take precautions, prepare, and evacuate if necessary (see Figure 2).
Second, accurate predictions about how storms are likely to act on particular coastlines can lead to strategies to minimize and mitigate such threats in the future with appropriate protective infrastructures.
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Three Mitigation Strategies
There are three strategies to build and maintain protective infrastructure that can reduce hurricane wave energy, coastal erosion, and flood hazards.
Natural infrastructure is defined as preexisting infrastructure, such as beaches, dunes, oyster and coral reefs, seagrass beds, barrier islands, mangroves, and salt marshes. One of the many ecosystem services that each of these provides is in slowing down the wave energy from storm surges and surface waves.
According to the National Oceanic and Atmospheric Administration (NOAA), public and private properties erected behind salt marshes see 20% less damage than properties where salt marshes have been removed. Citing The Nature Conservancy, NOAA’s Office for Coastal Management said salt marshes and other coastal wetlands helped prevent $625 million in property damage from Hurricane Sandy, which made landfall in New Jersey on October 29, 2012. Due to its size, ferocity, and 12-foot storm surge, Sandy still caused almost $70 billion in damages.
Unfortunately, natural infrastructure is on the decline. NOAA’s coastal office notes that New York’s Long Island Sound has lost 50% of its wetlands in the last 130 years.
Therefore, investing in “green” infrastructure—such as enhancing, protecting, and maintaining natural infrastructures—is crucial for minimizing flooding of coastal communities, coastal erosion, and damage to public and private property, researchers have advised (“Sustainability” Vol. 10, No. 2: 523).
Nature-based infrastructure can be defined as infrastructure that mimics characteristics of natural infrastructure but “is created by human design, engineering, and construction to provide specific services such as coastal risk reduction,” according to the researchers.
Beach nourishment is one approach to utilizing nature-based infrastructure.
For beach nourishment, forecasting is important in understanding what height is necessary for the beach and dunes to be effective in minimizing a storm's wave energy. The US Army Corps of Engineers (USACE) visually describes effective beach nourishment before and after the erosional effects of a storm surge in Figure 3.
This is an example during Hurricane Sandy how the Coastal Engineers at the USACE helped protect dunes and property from further erosion, decrease flooding, and limit how far ashore the storm surge could reach.
Grey infrastructure is a third strategy to mitigate impacts of hurricanes.
It can be defined as hard infrastructure put in place to minimize and prevent damage from natural disasters. Examples of grey infrastructure are seawalls, groins, breakwaters, surge barriers, and levees.
“Living shorelines” can be designed as a nature-based infrastructure, but they can also be engineered into existing grey infrastructure. A living shoreline uses natural, often locally sourced materials to create an infrastructure in the surf zones of various water bodies, from bays to inland waterways, according to The Apalachicola Times, which serves Franklin County, Florida.
These augmented shorelines can reduce erosion from storms while creating a habitat for coastal and marine species and plants, such as birds, fish, oysters, and seagrasses.
Weighing Choices Carefully
Some researchers (The Journal of Applied Ecology, 25 May 2020) warn against removal of natural infrastructures, saying living shorelines are important but not at the cost of already existing natural infrastructure.
An advantage of a living shoreline is that it can be implemented in a way to accommodate area usage. Living shorelines minimize everyday erosion, which is also necessary in slowing down the hurricane’s wave energy.
In contrast, natural infrastructure often takes up more space but proves very effective in extreme weather conditions such as hurricanes with their storm surges.
Coastal Population Growing
In the United States and around the world, there is plenty of infrastructure that needs to be improved so that coastal communities can be resilient in times of natural disasters.
The need is apparent—coastal populations continue to swell.
Already, in 1994, approximately 30% of the human population (2.07 billion) resided within 31 miles (50 km) from coasts, and nearly 44% (2.45 billion) within 93 miles (150 km) from coasts, said a new study in Nature.
When these coastal residential estimates were updated for 2018, “the coastal regions had grown to 2.86 billion (38.1% of global population) at 100 km [~62 miles] and 3.34 billion (44.6%) at 150 km,” wrote Mississippi State University sociologist Arthur G. Cosby and other members of the research team.
“Climate change has always been changing, and the human impacts on climate change are just one fraction of the net change,” predicts Prof. Kieu. “So, our best efforts to curb climate change do not mean climate change will stop. With the current warming rate, we cannot stop global warming fully, and so the warming trend will continue and introduce a shift in the frequency of extreme events. So, it appears that we will see more frequent extreme events, even with humans’ best efforts.”
As hurricanes create new opportunities to assess the ways to protect natural coasts and their infrastructures, the need to learn how to become ever more resilient during natural disasters is of paramount urgency.
*Laurie Burras is a former news editor for an international academic magazine. She currently resides in Philadelphia. Christopher Olson, a PhD candidate in civil engineering, contributed to this article.
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