New research by Virginia Tech scientists shows that sections of the Chesapeake Bay are sinking at rates of nearly a quarter an inch — or 7 millimeters — a year. Further, up-to-date knowledge of where the ground in the Chesapeake Bay area is sinking and by how much is not included in the official planning maps that authorities use to assess the local flooding risk from rising sea levels, the researchers said.
The region most at risk, the Naval Station Norfolk, home to the largest naval base in the world with a dense population of more than 1.7 million people.
Using radar imaging to measure elevation changes, Virginia Tech researchers have uncovered an important gap in planning for sea level rise in the Chesapeake Bay. In some areas, sea levels are rising at a faster rate than previously predicted because the land is sinking.
“By computing this radar measurement over a long time, we can measure the movement of the ground at a very high precision and accuracy,” explains Manoochehr Shirzaei, an associate professor of radar remote sensing engineering and environmental security in the Department of Geoscieces, part of the Virginia Tech College of Science, and a member of the Virginia Tech National Security Institute.
The Chesapeake Bay (CB) region of the United States is experiencing one of the fastest rates of relative sea-level rise on the Atlantic coast of the United States. However, future projections of sea-level rise (SLR) used to assess coastal flooding hazards and exposure throughout the 21st century often lack an accurate estimate of changes in land elevation. This poses a significant challenge to present and future management efforts because vertical land motion (VLM) can cause underestimation/overestimation of flooding risk to coastal communities. This work combines satellite data and in situ observations to measure VLM and assess 21st-century flooding hazards due to SLR, hurricane effect, and land elevation change in the CB. By the year 2100, the total inundated areas from SLR and subsidence are projected to be 454–600 kms for very low to very high greenhouse gas scenarios. The effect of storm surges associated with Hurricane Isabel can increase the inundated area to 849–1,117 km under different SLR scenarios and VLM. The results provided here inform policymakers when assessing hazards associated with global climate changes and local factors.
This poses a significant challenge to present and future management efforts as it could under or overestimate flooding risk to coastal communities along the stretch of Virginia shoreline, said Manoochehr Shirzaei, an associate professor of radar remote sensing engineering and environmental security in the Department of Geoscieces, part of the Virginia Tech College of Science, and a member of the Virginia Tech National Security Institute.
The new findings from the Virginia Tech Earth Observation and Innovation Lab appear in the Journal of Geophysical Research, with scientists having measured how much the land along the Chesapeake Bay’s shoreline has sunk using interferometric imaging with synthetic aperture radar from Earth orbit to detect elevation. The latter technique can measure year-to-year changes in local ground elevation as small as a millimeter, said Sonam Futi Sherpa, a doctoral student in the Department of Geosciences and lead author of the study.
This information on land subsidence along the coast, however, is not new, at least to the Cape Charles Mirror, which on February 6, 2022 had a post titled “Norfolk gets $14 billion to build flood wall,” wherein was stated that Norfolk has been identified as one of the most flood-vulnerable cities on the east coast, much of downtown has been built on fill, and the area is at risk because of sinking fill and rising water levels.
And prior to that, on October 20, 2019, the Cape Charles Mirror had a thread entitled “Opinion: The Great Democrat Climate Crisis Scam” wherein was stated as follows, to wit:
The land in the Chesapeake region has been sinking over the past 1,000 to 2,000 years, said Raymond G. Najjar Jr., a Pennsylvania State University oceanographer who has studied the impact of climate change on the mid-Atlantic coast, is a part of it.
And according to an article entitled “Atlantic coastline sinks as sea levels rise” by John Upton on Apr 16, 2016, we have as follows:
The main cause of East Coast subsidence is natural — the providential loss of an ice sheet.
Some 15,000 years ago, toward the end of an ice age, the Laurentide Ice Sheet stretched over most of Canada and down to modern-day New England and the Midwest.
Its heavy ice compressed the earth beneath it, causing surrounding land to curl upward.
Since the ice sheet melted, the land beneath it has been springing back up.
Like a see-saw, that’s causing areas south of the former ice sheet to sink back down, including Maryland, Virginia, and North Carolina.
The study shows that subsidence is occurring twice as fast now than in centuries past in a hot spot from Fredericksburg, Va. south to Charleston, which the scientists mostly blame on groundwater pumping.
“If you draw down your aquifer, the land above the aquifer kind of collapses,” said Timothy Dixon, a University of South Florida professor who helped produce the study.
“If that happens to be on the coast, that can also increase your flood potential.”
Virginia says it’s working on the problem.
“In most places, you wouldn’t notice it; it wouldn’t matter,” said Jack Eggleston, a U.S. Geological Survey scientists who has researched the effects of groundwater pumping on the region’s topography.
“But in terms of practical effects and practical problems, it does matter when you’re right on the shoreline.”