News Release

Critical observations of sinking coasts

Peer-Reviewed Publication

Virginia Tech

Leonard Ohenhen

image: Using satellite-obtained data, Leonard Ohenhen mapped the entire East Coast to demonstrate how the inclusion of land subsidence reveals many areas to be more vulnerable to floods and erosion than previously thought. Photo by Christina Franusich for Virginia Tech. view more 

Credit: Virginia Tech

It’s been said that a rug can really tie a room together. In a similar fashion, Manoochehr Shirzaei and his research team are hoping that weaving together millions of data points into terrain-covering, digital maps can help connect the realities of sinking landscapes to the overall impact of climate change.

“It’s like a carpet over the desert,” Shirzaei, associate professor of radar remote sensing engineering and environmental security, said of a recent projection of land in Arizona. “You can clearly see that area is just massively sinking into the ground. And we’ve created these maps for dozens of major cities in the United States and monitor another 50 airports globally.”

Using publicly available satellite imagery, Shirzaei and the 15 student and postdoctoral researchers at Virginia Tech’s Earth Observation and Innovation Lab measure millions of occurrences of sinking land, known as land subsidence, spanning multiple years. They then create some of the world’s first high-resolution depictions of the land subsidence, which when combined with other observations, such as sea-level rise, provide more clear projection of the potential impact of floods and natural disasters during the next 100 years.

Most recently, the lab’s mapping served as the foundation for graduate student Leonard Ohenhen’s findings published in Nature Communications, a British science journal. Using satellite-obtained data from 2007-21, Ohenhen mapped the entire East Coast to demonstrate how the inclusion of land subsidence reveals many areas to be more vulnerable to floods and erosion than previously thought.

“We saw places like New York City and Charleston [South Carolina] are sinking up to as much as two millimeters per year,” said Ohenhen, one of the lab’s graduate students. “It really shows the hidden vulnerability of the Atlantic East Coast to sea-level rise.”

The unique, high-resolution maps crafted in the Earth Observation and Innovation Lab also have drawn the attention of multiple government agencies. This has led to the investment of millions of external dollars in an effort fill a critical gap of information and help people better plan at the local, state, federal, and global level.

“One of the big uncertainties we have is how the land is moving up or down through time, so we’ve turned to Manoo,” said Patrick Barnard, a research geologist with the United States Geologic Service (USGS). “This information is needed, no one else is providing it, and Manoo’s stepped into that niche with his technical expertise and is providing something extremely valuable.”

Land movement can be the result of natural processes, such as tectonics, glacial isostatic adjustment, sediment loading, and soil compaction, but can also result from human behaviors, such as extracting groundwater and gas and oil production.

Barnard said the vertical land motion rates provided have helped the USGS produce better models and give better guidance to other agencies in terms of managing and mitigating the risk of flooding. This impacts everything from real estate values and building plans to hurricane evacuation routes and the location of future levees.

The Earth Observation and Innovation Lab played a key role in recent USGS projections of future hazards on the Atlantic coast. The project consists of several data sets that map future coastal flooding and erosion hazards due to sea level rise and storms for Florida, Georgia, and Virginia with a range of plausible scenarios through 2100.

“Having this collaboration helps us refine the risk to lives and dollars communities face from sea level rise and storms," Barnard said. “This is a really valuable data set they provide.”

Bringing such realities into focus for the average person is at the heart of Shirzaei’s efforts and the work of the lab.

“We’re creating access to actionable data that will help people become resilient when it comes to national and environmental security,” Shirzaei said. “The data we’re providing, we’re making it more than just open access, we’re making it usable by everybody. You don’t have to have a Ph.D. to use it. That’s our niche here.”

Shirzaei joined the College of Science in fall 2020, alongside his spouse, Susanna Werth, assistant professor of hydrology and remote sensing. Shirzaei’s Earth Observation and Innovation Lab and Werth’s Hydrologic Innovation and Remote Sensing Lab work in tandem, utilizing the same space, much of the same technology, and even sharing student researchers.

Having previously worked together in Arizona, the pair was drawn across the country by the community feel they found in the New River Valley.

“Virginia Tech is a great school, but what we really like is the environment Blacksburg provides for our family,” Shirzaei said.

Both students of geodesy — the science of modeling the geometry, gravity, and spatial orientation of the Earth — Werth said their work with remote sensing methods from satellites taps into interests that she’d long had.

“I was always very fascinated with observing stuff from space, how without touching the ground, you can see somethings there so much better,” Werth said. “And I was also very fascinated by water, so observing the water cycle with space observation methods is ideal.”

Shirzaei said he was first turned on to the idea of using satellite data to observe the Earth, rather than going out to physical locations, during a geophysics and remote sensning conference about 20 years ago.

“I saw everyone like me dirty coming in from field work except for a bunch of Italian guys in ties and suits," he said. “Their hands were clean. They smelled like perfume. And I said, I want to be these guys.”

The group presented a paper on using Interferometric Synthetic Aperture Radar, commonly called InSAR, obtained from satellites. InSAR makes high-density measurements over large areas by using radar to measure changes in land-surface altitude at high degrees of measurement resolution and spatial detail.

Shirzaei jumped at the opportunity to learn this new research method, but faced initial hurdles due to his Iranian citizenship.

“Now I’m an American, but at the time, if I wanted to access the data, just me emailing one of them would have been a violation,” Shirzaei said. “So I had to build everything myself and I began writing code from scratch. It took a little bit longer, but I think it was good for me.”

The tools Shirzaei developed provided the foundation for the Earth Observation and Innovation Lab, which he said is constantly evolving based on the most relevant problems that need to be solved.

“This data has been around for years. What’s made the data revolutionary is the way we process them,” Shirzaei said. “To get these kinds of maps, you need a technology that is rare. And then, all we do is look for a good niche application to add value to it and communicate that to people.”

The lab’s current projects include:

  • A $3.3 million Department of Defense project to predict flooding at U.S. Army bases across the globe.
  • A $1.75 million Department of Energy project to study the impact of fluid injection on land elevation change and earthquake hazards.
  • A $1.5 million National Science Foundation project to study the impact of ecosystem-based solutions on protecting coastal communities.

“We are funded by tax dollars, so we really want to make sure our work is relevant for tax payers,” Shirzaei said. “For that reason, I’ve completely changed my lab’s direction serval times over the past eight or nine years. Because the mission is important, it’s worth the risk.”

The lab’s mission has drawn the interest of a diverse population of student researchers. Students like Sonam Sherpa, a graduate student who followed Shirzaei from Arizona, and Mohammad Khorrami, a graduate student who changed his major as a result of the lab experience, make up a team of students representing eight different nationalities.

“That helps understanding how different groups in the world perceive the challenge we face, especially with sea level rising,” said Oluwaseyi Dasho, one of the lab’s graduate student researchers. “It really helps us further solve these problems.”

Shirzaei said the lab has the funding and workload to support as many as 25 students and hopes to expand as soon as the physical space allows for it. It plans to relocate to the Virginia Tech Corporate Research Center in May.

The Earth Observation and Innovation Lab is the reason Ohenhen decided to attend Virginia Tech. He said working in the lab not only allows him to do the type of research in his recently published paper, but it also echoes his passion for helping communicate actionable information to others.

Along with flood projections for the entire East Coast, part of the paper published in Nature highlights the vulnerability of the wetlands, which often provide a barrier between floods and people by absorbing flood waters slowly. Ohenhen said he hopes his research makes clear that ecosystem’s importance to the residents of those areas.

“Protect the wetlands is the overall message to the average person,” Ohenhen said. “Most people, they try to protect just enough of their property and leave other areas like the wetlands to basically fend for own survival. But when we do that, we’re really just creating a greater threat for ourselves.”

Shirzaei said he hopes the maps created for Ohenhen’s paper are used by policymakers and leaders to prevent areas from remaining undefended from flood waters. Similarly, he hopes the Earth Observation and Innovation Lab as a whole continues to be utilized in ways that help people better understand and prepare for potential risks.

“At the moment, the problem a lot of people have is they don’t know the hazard that might come in the future,” Shirzaei said. “Our data will help them understand that and come up with better plans for the future.”


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