By Steven Bradley
Photography by Josh Wilson, Tom O’HalloranBrian Williams

Thirty years after Hurricane Hugo, Clemson’s Baruch Institute is still in the trenches of hurricane research

At 2 parts per thousand of salt water, the bald cypress are already severely stressed. Once the chloride concentration reaches 4, the trees are on their way out. And those, the species that lend cypress swamps their name for their ubiquity, are the last to go. The swamp tupelos, red maples and black gums have long since succumbed. By 5, the tidal freshwater forested wetland ecosystem is gone, replaced by salt marsh or open water.

Salt water encroachment due to sea level rise — driven by a more variable global climate system, along with tidal surges caused by hurricanes that carry salt water into the forest to infiltrate the soil — is killing off coastal forests across the American Gulf and Atlantic coasts.

While the death of a swamp might not seem like cause for concern to some, the wading birds, fish, reptiles, deer and bear that call it home are sure to have a different view. Those who care about preserving an iconic part of the coastal landscape of the Deep South, too.

But as coastal forests fight this losing battle against the sea, Clemson University researchers at the Belle W. Baruch Institute of Coastal Ecology and Forest Science in Georgetown, S.C., are working to level the playing field.

When Hurricane Hugo crashed into the South Carolina coast as midnight approached on Sept. 21, 1989, its maximum sustained wind speed of just over 135 mph is the highest on record for a hurricane in South Carolina, according to the state climatology office. Massive 20-foot storm tides — the highest ever recorded on the East Coast — slammed Bulls Bay just north of Charleston.

RISING TIDE

Rising sea level in low-lying ecosystems along America’s southeastern Atlantic and Gulf coasts are converting freshwater forested wetlands into salt marsh, leaving behind what scientists have dubbed “ghost forests.” And at Winyah Bay in northeastern South Carolina, sea level is rising by an average of 3-4 millimeters per year. That translates to about 24 centimeters — not quite 10 inches — over 60 years.

While less than a foot across six decades may seem insignificant, remember why it is called the South Carolina Lowcountry. Large infrequent disturbances such as hurricanes also significantly alter coastal forests through damaging winds and salt water carried inland with the storm surge. Hurricanes are increasing in both frequency and intensity with a more variable climate system, and, in turn, scientists expect increasing sea level rise and enhanced opportunity for saltwater intrusion.

And while sea level rise is an expected consequence of climate change — more intense storms push salt water further inland, while increasing droughts slow the outbound flow — it’s also a result that could have devastating consequences to ecosystems across the southeastern U.S.

Sea level is expected to rise 0.48 meters with a range between 0.11 and 0.77 meters by the year 2100, but some believe that estimation may be conservative and the range could be as large as from 0.5 to 1.4 meters. Approximately 58,000 square kilometers, more than 22,000 square miles, of land along the Atlantic and Gulf coasts lies below the 1.5-meter contour, dangerously close to the tipping point where land begins being reclaimed by sea.

“In either case, sea level rise under a changing climate is of a great concern to low-lying states in the southeastern United States with large coastal wetlands, including North and South Carolina, Louisiana, Florida and Texas,” Baruch researchers Tom Williams, Alex Chow and Bo Song wrote in a 2012 research report.

THE PROBLEM WITH HURRICANES

Equipped with a Ph.D. and work experience in forested wetlands, William Conner arrived on Hobcaw Barony in the fall of 1989 for a job interview two weeks after Hugo passed through.

But Hugo wasn’t a competing candidate or a fellow scientist, even though Conner and his soon-to-be colleagues would spend a great deal of time over the ensuing three decades in collaboration with him, so to speak.

When Hurricane Hugo crashed into the South Carolina coast as midnight approached on Sept. 21, 1989, its maximum sustained wind speed of just over 135 mph is the highest on record for a hurricane in South Carolina, according to the state climatology office. Causing $9.5 billion in damage, Hugo was the costliest storm in American history. Massive 20-foot storm tides — the highest ever recorded on the East Coast — slammed Bulls Bay just north of Charleston. All told, 61 deaths were attributed to the storm.

Wind gusts of 120 mph were recorded by a boat, the Snow Goose, anchored near Georgetown along the Sampit River. The Sampit flows into Winyah Bay, the water that forms the eastern border of the Baruch Institute, about 65 miles north of Charleston.

“I moved here in February of 1990,” Conner says, “and the main emphasis of everybody around was Hugo research and how were the forests going to respond with that disturbance and how long was it going to take for them to recover.”

But the problem with answering that question, and the problem with studying hurricanes in general, from a scientific perspective, is one of opportunity.

While hurricanes often generate a great deal of immediate interest following landfall, little was actually known about their long-term impacts on forested wetlands prior to Hugo, primarily because it is difficult to prepare an area to study since it cannot be predicted when or where a hurricane will hit, and time and money are needed to design and implement a study once one does occur.

“It is often easier to study something else and hope that others will follow up on the questions that have been raised,” Tom Williams wrote in a 1998 study on hurricane impacts on Atlantic and Gulf coastal forests. “Special emphasis will be placed on Hurricane Hugo, as it may provide the best opportunity for long-term ecological research in the coming years.”

And Williams was not alone among Baruch scientists realizing the golden opportunity that Hugo afforded.

“Sea level rise under a changing climate is of a great concern to low-lying states in the southeastern United States with large coastal wetlands, including North and South Carolina, Louisiana, Florida and Texas.” Baruch researchers Tom Williams, Alex Chow and Bo Song wrote in a 2012 research report.

TWENTY-SEVEN YEARS OF RESEARCH

Early wildlife research in the aftermath of Hugo was done by now-retired faculty member Gene Wood, who sought to understand the effects of the hurricane on Hobcaw’s wildlife populations, notably red-cockaded woodpeckers, deer, wild turkeys, feral swine and fox squirrels.

“Dr. Wood had a technician whose job was quite literally to get up every morning in the dark, go out to a particular nest tree where he would have to wait for the bird to come out and then follow them through the woods and, through binoculars as best he could, record what they were eating and where they were,” says George Askew, then Baruch Institute director and now Clemson’s vice president for Public Service and Agriculture. “We did not have a lot of fancy dollars to do fancy stuff. It was all extremely old school.”

That type of old-school science suited Conner just fine, and through a grant from the U.S. Forest Service in Charleston, he set about installing research plots on the Baruch property — three that had been hit hard by Hugo and one control site with the aim of understanding saltwater intrusion. The question, specifically: How much salt does it take to affect vegetation?

Even now, though the research was published in 1992, he can rattle off the figures for specific tree species without blinking: “The bald cypress are pretty much the last tree species to go in this process of increasing sea level and saltwater concentration. Even at that, the cypress are severely stressed at as low as 2 parts per thousand and by 4 parts per thousand are on their way out to be replaced by marsh or open water.”

Clemson forest ecologist Charles Gresham and hydrologist Tom Williams set to work studying the Hobcaw systems that were still in place, and Gresham ultimately put together a system of forest inventory and plots both on Hobcaw and on corresponding plots across the state where the hurricane had left its mark.

After Gresham retired, associate professor and forest scientist Bo Song took over the project as principal investigator. Her team has continued working on data collection both in the field and using remote sensing derived data.

With funding from the Andrew W. Mellon Foundation, Gresham and Song’s monitoring of coastal forests has continued for 27 years, producing 16 peer-reviewed publications and 10 presentations at professional conferences or to the public. The research not only provides insights to the long-term recovery of natural forest ecosystems after major disturbances but also contributes knowledge on the potential effects of global climate change on coastal forest structure.

“Knowing how coastal forests respond to major hurricanes in the long term and short term will aid us in preparing for future hurricanes and for potential changes in disturbance regimes,” Song says.

This examination of almost three decades of recovery trends of five forest types from four sites after Hurricane Hugo — focused primarily on forest composition, structure and species change — has added to the understanding of the long-term impacts that hurricanes may have on temperate forest ecosystems.

Effectively, research conducted at the Baruch Institute has built a knowledge base for the study of saltwater intrusion, sea level rise and hurricane impact on coastal forests where one did not exist before.

Perhaps more importantly, it has laid the groundwork for generations of future hurricane work by filling in knowledge gaps on forest recovery that can help inform the conservation and management of coastal landscapes that are essential to the environmental health and economic prosperity of the South Carolina Lowcountry and its citizens.

“Our mission is to provide scientific research that supports sustainable coastal resource management,” says Skip Van Bloem, professor and Baruch Institute director. “To understand sustainable management, you have to understand how large disturbances will affect coastal environments and then how management decisions should be made in response to those and also in preparation for that.”

MODERN METHODS

The term “tidal freshwater forested wetlands” was not one used in the scientific community prior to 2007, when results from a study by Conner in collaboration with the U.S. Geological Survey were published. “At that point in time, we sort of introduced that term to the world,” Conner says.

What the Clemson researchers are learning about those ecosystems is important to anyone interested in preserving the distinct lifestyle, environment and economy engrained in South Carolina’s Lowcountry and so many other coastal locales around the globe.

“The marshes are just really important for sea life — for the fish and the shellfish we’re used to catching and eating in the Lowcountry,” says Tom O’Halloran, an assistant professor stationed at Baruch. “So many of their life cycles depend on the marsh. Some part of their life cycle happens in the marsh; they’re born there or they eat there, or they reproduce there.

“People are going out and catching redfish and flounder and have been doing it for generations. There are still quite a few people making a living off those fisheries. So, if those marshes drown — if sea level rise puts them under water and they don’t go into the forest — then we’re in real trouble in terms of the fisheries that we depend on at the coast.”

And like it or not, researchers at the Baruch Institute have had plenty of chances to continue their hurricane studies since Hugo as more massive storms have rolled through: Floyd, Bonnie and Charlie in the 1990s and 2000s, and Joaquin, Matthew, Irma, Florence and Dorian have come in spate each year since 2015.

O’Halloran, for his part, has a reputation for using cutting-edge tools to take research at Baruch into the next generation, in this case, using drone technology to make a mosaic documenting the sea level rise along the 2-mile stretch of coastline on Hobcaw Barony.

“This is so high resolution you could zoom and count the leaves on the tree,” he says. “This idea of using drones to do this kind of rapid deployment, really high resolution, watching these kind of transitions, really enhances our ability to study sea level rise in an efficient manner.”

And Baruch scientists continue to pursue new and more efficient avenues to study the recovery of coastal ecosystems from hurricanes and other extreme weather events. Through a grant award from the National Science Foundation’s Rapid Response Research (RAPID) program, four Clemson researchers — O’Halloran, Conner, Song and Van Bloem — are taking the hurricane research to another level by studying impact of storm surge on coastal forest demography in response to repeated hurricane disturbances.

The reason is simple: Much of the theory devoted to hurricane disturbance effects on coastal forest ecosystems arises from the study of single hurricanes or immediate response following the hurricane.

The researchers aim to leverage data and research sites from Gresham and Song’s long-term field study of coastal ecosystems to examine the consequences of Hurricane Hugo on the recovery from wind throw and salt stress, while using remote sensing to assess forest structure, stress and other plant traits across the marsh/forest landscape and at multiple study areas along the coast of South Carolina.

AN ECOSYSTEM REMEMBERS

As technology and research methods have advanced, so has the Baruch property changed in the past 30 years, Conner says. But the long-term scientific studies that he helped put into place are helping researchers understand those severe events and their impact.

“In some of the areas where we were working, it killed about 98 percent of the trees, which is a big impact,” he says. “What we’ve seen in 30 years after Hugo, in those little wetland systems, the trees that weren’t killed ended up producing seeds. We have new trees starting to come in, and we’re now starting to see the canopy closing back in, starting to get a real nice forest back in, but it’s going to take another 30 to 50 years before it looks anything close to what it was before the storm.

“Hopefully, the people who come after me will be the ones to see the final result,” he adds. “Hopefully, eventually it’ll look like that out there again one day.”

But even if all those trees grow back and that canopy closes in, the impact of Hugo on the coast of South Carolina and, in turn, the research that has taken place on Hobcaw Barony, are forever etched into the memory of its citizens and scientists … and ecosystems.

“These big events are placemarkers in your memory,” Van Bloem says. “You can talk to folks here and say, ‘Where were you when Hurricane Hugo happened?’ Everybody remembers exactly what they were doing and exactly what happened.

“These are natural events that do the same thing. And an ecosystem remembers that too, right? Because that’s a starting point or sometimes an ending point for natural systems, too.”

WHEN EVACUATION IS THE ANSWER

A challenge during hurricanes and other hazards is the evacuation of massive numbers of people. Pamela Murray-Tuite, associate professor of civil engineering, is the co-author of Large-scale evacuation: The analysis, modeling, and management of emergency relocation from hazardous areas (Taylor and Francis, 2019; Lindell, M. K., Murray-Tuite, P., Wolshon, B., & Baker, E. J.). She shared with us some important lessons learned about mass evacuations through research and modeling.

When we talk about evacuation, what hazards are you considering?

A:  Evacuation can apply to any hazard for which it is a safer course of action to move from a threatened area than to remain. Hazards that typically come to mind are fires, floods, hurricanes, tsunamis, nuclear power plant incidents and some hazardous materials releases. Each hazard has different characteristics and challenges, such as the amount of advanced warning, size of the affected area and the distance to safety.

What are some practical things we should remember when authorities in our area are calling for evacuation?

A:  First, recognize that authorities do not make evacuation recommendations lightly. Evacuations can be expensive, and if the hazard does not hit, local areas may face challenges with reimbursement. The authorities do not want to unnecessarily worry or inconvenience their citizens. There are two ways for authorities to be considered “wrong” — issuing evacuation notices and the hazard does not hit the area and failing to issue evacuation notices for a hazard that does strike. The first error type still preserves the safety of the public, while the latter has life-safety consequences. No one knows exactly what is going to happen. When an evacuation notice is provided, it is important to pay attention.

Second, for a large-scale hazard (e.g., hurricane), remember that many people are in the same situation. They may have similar preferences, such as daylight departure and arrival or not evacuating until some of the uncertainty is resolved. Much of the congestion associated with evacuations is due to demand exceeding capacity. Evacuating earlier — be it days in advance or earlier on a given day (say around 4 a.m.) — can help alleviate some congestion. Congestion also increases fuel/energy consumption; when magnified by a large number of travelers, fuel shortages are a possibility.

Finally, recognize that your decisions affect others. Neighbors may observe you evacuating and use this as a cue to behavior they may want to consider. The aggregate decisions of the population largely affect how successful (or not) the evacuation is considered.

What are some of the lessons have we learned since Hurricane Katrina and other similar events?

A:  Each event is unique and brings opportunities to learn about and make improvements to disaster management. Sometimes, evacuation is not the best course of action, depending on the hazard, location and time to impact. Although there are many lessons learned from high-profile evacuations, only four are discussed here:

Hazards can be compounded. During Hurricane Katrina, the hurricane led to an evacuation, but a second evacuation was needed when the levees failed and flooded much of New Orleans. In 2011, an earthquake off the coast of Japan triggered a tsunami that exceeded the sea wall protection built for the Fukushima Daiichi Nuclear Power Plant. The water led to several issues with generators used for cooling, eventually leading to meltdowns and radiation releases. Multiple sets of evacuations were needed for the power plant issues as well as the tsunami. Finally, although it is well recognized that hurricanes bring strong wind and storm surge and are accompanied by rain, the potential magnitude of that rain was highlighted in Hurricane Harvey. This storm, which delivered over 40 inches of rain, led to thousands of rescues.

Not every household has a reliable vehicle for evacuation. The evacuation for Hurricane Katrina worked fairly well for those who were able to self-evacuate in their own vehicles. However, Hurricane Katrina highlighted that carless households could be geographically clustered, making it challenging to obtain rides. Overall, better planning was needed for those who could not evacuate themselves.

Actions taken to address transportation issues for a normal day can affect evacuation performance. The wildfire known as the Camp Fire in 2018 highlighted this issue. One of the main evacuation routes had been intentionally narrowed to improve safety and reduce the number of vehicles able to use the road.  (St. John et al., 2018).  Addressing evacuation needs during development and when modifying the transportation system could lead to improved evacuation outcomes.

Clear communication is crucial. Communication surrounding an evacuation should clearly state who is issuing warnings, what the hazard is, at-risk locations and populations, when the hazard should arrive, how probable it is, the specific recommended protective actions, and where to find additional information and sources of assistance. (Lindell et al., 2019).  Clear messaging can help encourage those who should evacuate to recognize that this is the recommended protective action for them. Clear messaging can also help reduce shadow evacuation (people from low-risk areas evacuating), which can delay travel for those at higher risk. The information should also be communicated in multiple languages, reflecting the resident and tourist populations, and disseminated through multiple channels since communication technology preferences differ.

References:

Drabek, T. E. (1999). Understanding disaster warning responses. The Social Science Journal, 36(3), 515-523.

Lindell, M. K., Murray-Tuite, P., Wolshon, B., & Baker, E. J. (2019). Large-scale evacuation: The analysis, modeling, and management of emergency relocation from hazardous areas. Taylor and Francis.

Lindell, M. K., & Prater, C. S. (2007). Critical behavioral assumptions in evacuation time estimate analysis for private vehicles: Examples from hurricane research and planning. Journal of Urban Planning and Development, 133(1), 18-29.

St. John, P., Serna, J., & Lin, R.-G. (2018). Must Reads: Here’s how Paradise ignored warnings and became a deathtrap. Los Angeles Times. https://www.latimes.com/local/california/la-me-camp-fire-deathtrap-20181230-story.html.

Trainor, J. E., Murray-Tuite, P., Edara, P., Fallah-Fini, S., & Triantis, K. (2013). Interdisciplinary approach to evacuation modeling. Natural Hazards Review, 14(3), 151-162.

Steven Bradley is a news editor and writer for Clemson Public Service and Agriculture.

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