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.