The Rise and Fall of the Chesapeake Bay
The last house on Holland Island. Image sourced from Atlas Obscura.
Hello again! This is the second part of a series focusing on the Chesapeake Bay as a current benefactor to use InSAR as an additional tool. This, for a change, will not be technical but rather a collection of real stories that show why this technique is important.
Frequent Flooding
As each year passes, more and more communities worldwide are experiencing frequent flooding due to sea-level rise (SLR). Coastal communities along the Chesapeake Bay are not an exception. These communities thrive off of the world’s third largest estuary and have been impacted severely. Some of the heavily populated areas throughout this region have management plans backed with data to combat SLR, while many of the smaller coastal communities are left in the dark. Outside of the Chesapeake Bay region, InSAR is a valuable tool used to evaluate SLR scenarios through land deformation by identifying projected inundated areas and flood vulnerability to specific communities both big and small.
Aerial image of the Chesapeake Bay and its surrounding tributaries. Original image sourced from Penn State University News, labeling added by Brooke Haas.
Lost Treasures
Growing up 20 years ago, unless a hurricane passed through, it would rarely flood at my river house in the Northern Neck of Virginia. Presently, it floods every month from consistent winds forcing the Bay water upriver during high tide. Over the years, my family and neighbors have had to adapt to this new phenomenon with creative ideas; lifting laundry machines off the garage floor onto pallets, bolting/tying down items on decks and docks to prevent them from floating away, and extending well pipes to prevent intruding saltwater. Some homeowners have even lifted their houses off the ground in desperate attempts to evade destructive flooding. We are not the only ones experiencing these recurring events, some communities have been battling this issue for decades. In the middle of the Chesapeake Bay, lie the remains of Holland Island. In the early 1900’s, it was once a thriving community but is now lost to the Bay. Due to SLR, one of the last remaining islands is currently disappearing with every high tide. Along with Holland Island, the historical Tangier Island will be lost forever within the next 45 years.
**The photos shown below were taken by my parents during a flood at our river house in Northern Neck of Virginia on 12 October 2019. Abnormally high tides, one meter above normal, were caused by both the Hunter’s moon phase and storm surge from Tropical Storm Melissa.
At 1.7 mm/yr, SLR is affecting coastlines all over the world, but in the Chesapeake Bay it is rising faster than any area on the U.S. - Atlantic coast. Its relative sea-level rise (RSLR) trend shows that the Bay is double the global average rate at 3.2 mm/yr, with some places seeing as high as 6 mm/yr. This is mainly the result of subsidence that is driven by aquifer depletion and glacial isostatic adjustment (Chesapeake ODU). These factors working together highlight the Bay region as a hot spot. Its invading brackish waters are creating landslides and causing salinization of soil, making farmland unusable and worthless. It is contaminating aquifers that supply water to over 18 million people living within the Bay’s watershed. Low-lying areas, farms, and homes will have to be relocated as the bay floods the adjacent land (Nat Geo).
Low-lying cornfields near the Chesapeake Bay are inundated with saltwater (image sourced from The Atlantic).
Discoveries and Decisions
Knowing that land subsidence contributes to RSLR in the region, it is important to understand why, where, and how fast it is occurring, now and in the future. There is currently not enough data to fully realize what is going on here. Accurate and precise measurements and tools are needed to improve our understanding. InSAR could discover and identify unexpected areas of subsidence, shifting the focus to other equally important hot spots in need of attention in the Chesapeake Bay.
Unaware of the land deformation on our street, my family as well as my neighbors are making mistakes by finding quick fixes to battle the floods. For instance, as I mentioned earlier, some homeowners on our peninsula have lifted their homes off of the ground away from flood waters. Rather than keeping the homes on stilts, they have enclosed the new ground level with rebar reinforced concrete block. This is adding twice as much weight and pressure, gradually pushing the ground closer to sea-level. To combat RSLR the right way, it is vital to incorporate InSAR’s subsidence data into the decisions that will be made in the near future by my family, neighbors, and others throughout the Chesapeake Bay communities.
Together, RSLR and subsidence will inevitably allow saltwater to trespass onto our properties faster than the areas around us, slowly eroding the shore with every storm that passes. Before jumping into saving what is left of our land, it is important to understand and accept this reality. Only then can we explore the appropriate options towards resilience. With an issue this urgent and regionally widespread, it is vital to build a strong foundation of scientific understanding to make better decisions. It will take more than a village to triumph, so it is a good thing we have reliable, shiny friends checking in on us from above.
Our guest author, Brooke Haas
Brooke Haas is an educator and writer based in Roanoke, VA. She has worked on both research vessels and oyster boats and holds a B.S. in Biology from Old Dominion University.