The storm's human toll was monumental: a path of destruction through a dozen East Coast states; 122 people dead, 48 in Pennsylvania alone; and $3.1 billion in damage. It was the nation's costliest natural disaster at the time.
And the environmental consequences, in the eyes of contemporary observers, were simply unimaginable: a shock wave of filthy water pummeling the Chesapeake Bay from nearly every direction, replacing its fragile balance with chaos.
In some ways, North America's largest estuary, experts say, has never been the same.
"What's interesting, given that it's 50 years later, is we still see some of these alterations that have persisted," said Rom Lipcius, a longtime scientist with the Virginia Institute of Marine Science. "A lot of [the memories] have faded. The historical baseline shifts, and we think this is the way it's always been. And that's just not the case."
With half of a century's worth of perspective, let's look back at how the ecological blow from a devastatingly wet week continues to echo across the Chesapeake and its watershed.
Bay's problems become 'real'
Agnes forever altered the way the public regarded the Chesapeake Bay. And as the fourth employee at the Chesapeake Bay Foundation, Mary Tod Winchester had a front-row seat for the shift.
She grew up on the West River in Galesville, MD, a member of a family that has owned and operated a boatyard on the waterway for eight generations.
"When I was growing up, obviously, [the Bay] was really pretty healthy," Winchester recalled. "And then in the '60s is when we really noticed a change."
Underwater grasses, the centerpiece of the Bay's food web, were dying off. Problems such as diseases and overharvesting had ravaged oysters, crabs, clams and other important fisheries. But beyond a relatively small group of scientists and activists, few people paid much heed to the estuary's growing ecological woes, Winchester said.
"And that was one of the things about Agnes," she said. "It was a wake-up call, and it really helped to ring the bells that there was a problem here."
Swirling and twisting its way northward from the Gulf of Mexico, Agnes could only muster sustained winds of 45 mph by the time it reached the Chesapeake region. But it literally rewrote the books on rainfall. The system stalled over the Susquehanna River basin June 21–24, dropping, dropping as much as 18 inches of rain.
Agnes heralded a decade of soggy weather and unusually high river flows, which unleashed tons of nutrients and sediment into the beleaguered Bay. As a result, Winchester said, the public and their elected representatives could no longer ignore the environmental disaster unfolding before their eyes.
"Everyone began to realize how important it was for Pennsylvania, Maryland and Virginia to be working together on Bay issues," she said.
The Chesapeake Research Consortium, a hub for Bay-related research, was born in the immediate aftermath of Agnes as scientists scrambled to understand the full breadth of its impact. By the end of the decade, Congress acted, funding a five-year, $27 million study to examine the Bay's rapid deterioration.
Winchester stayed with the Bay Foundation for more than 40 years, rising from the executive director's secretary in 1971 to vice president of administration. There were several important milestones as the advocacy group flowered into a powerful regional political force with nearly $30 million in annual revenue. But Agnes was certainly one of them, she said.
"It helped to energize CBF," she said of the organization, which formed in 1966. "It helped us show the public we're not just a bunch of hippies trying to say the Bay is dying and raising money so that we can, you know, pay people to have jobs. Agnes made it real."
Clamming up
Rarely is a single event to blame for the decline of a species. One exception may be the soft shell clam population of the Chesapeake Bay.
Soft shells (Mya arenaria), named for their brittle, oval shells, were so abundant in the Bay region during the 1950s and '60s that Maryland crowned an annual "clam queen" to promote the vibrant fishery. Their meat has been sought over the years as a staple in New England-style stews and for baiting blue crab pots.
Annual clam landings peaked in the state at 680,000 bushels in 1964 but remained higher than 500,000 through 1971.
Agnes' consequences were immediate and devastating. The storm delivered an onslaught of sediment to the Bay, slathering most of the clam's bottom habitat with a layer of thick mud.
About nine out of 10 soft clams died from the suspected combined stress of low salinity and abnormally high water temperatures, according to the Chesapeake Research Consortium. Scientists conducting painstaking surveys failed to locate a single living soft clam in the Rhode and South rivers near Annapolis in the months after the storm.
Maryland authorities temporarily banned clamming three months after the storm to promote its recovery. Over the next two decades, the population perked up somewhat but nowhere near its pre-Agnes levels. Today, the fishery is classified as a remnant of its former self.
Diseases and worsening water quality certainly played roles in suppressing the clam's numbers, experts say. But computer modeling by Lipcius and some of his colleagues suggests that Agnes was the tipping point for clams.
Blue crabs had always been one of their major predators. But with clam numbers significantly thinned after the storm, they couldn't reproduce enough to outpace the crabs' appetite.
"So, those are two species that got hit—one that has never recovered and one that did recover," Lipcius said.
The downfall of underwater grass
Beneath its surface, the Chesapeake Bay once abounded with a rich panoply of plants that thrive underwater. So, could a burst of additional water be a bad thing?
Agnes underscored that it can be.
The Bay's grass acreage had begun to backslide in the 1960s. Then Agnes wiped out about half of what was left, accelerating that downward trajectory in a phenomenon "unprecedented in the Bay's recorded history," wrote VIMS researchers Bob Orth and Kenneth Moore in an influential 1983 study. Unlike previous downturns, the 1970s die-off appeared to strike not just one plant species or one localized area but all species across the Bay, they said.
The submerged meadows are among the most crucial indicators of Bay health because they require clear water to survive. Under the Bay's multistate and federal restoration effort, nutrient-reduction goals are aimed at improving water clarity enough to reach a goal of 185,000 acres of grasses covering its bottom.
In 2020, VIMS mapped a total of just 62,000 acres, barely one-third of the targeted amount. In the nearly 40 years since the Bay cleanup formally launched, the underwater plant coverage has had its ups and downs but has never surpassed 110,000 acres.
The persistently disappointing vegetation data likely contain a faint echo from Agnes, said Andrew Dehoff, executive director of the Susquehanna River Basin Commission, a state-federal compact with the authority to regulate water use within the river's 27,510-square-mile watershed. Had Agnes arrived at another time of year, the grasses, he said, might not have fared so poorly.
"The impact to the Bay was quite significant because the delivery of sediments and nutrient loads occurred in June, the critical part of the growing season for submerged grasses," Dehoff said. "Vegetation was inundated. And that's very difficult to recover from."
'Last nail' for shad
Inside a musty-smelling cannery that has been transformed into a museum for antique Chesapeake Bay workboats, Pete Lesher fixed his attention on one of the smallest vessels in the collection.
If paint had ever clung to its wooden surface, it has long since rubbed off. A sign gives its dimensions as 18 feet, 9 inches in length and 5 feet at its widest. But the most important feature, in Lesher's eyes, is its completely flat bottom, which ensured maximum stability and allowed it to be hauled directly onto the shore, if necessary.
Lesher, the chief curator for the Chesapeake Bay Maritime Museum in St. Michaels, MD, explained that this rustic-looking skiff was designed and built with a singular purpose: netting American shad from the Eastern Shore's Choptank River.
"Little local variations are these expressions of local culture," he said. "Note," he went on, "the way they specifically shaped this boat for this fishery in this place, the length of boat determined by the length of net that they're going to use, the depth of net determined by the depth of water."
After Agnes, Lesher added, this boat was pretty much obsolete.
Shad once numbered in the tens of millions during their spring spawning runs up the Chesapeake's rivers. But overfishing, increasing water pollution and dam construction sent their population into a downward spiral during the middle of the last century. Agnes all but finished it off, experts say.
"Agnes was the last nail in the coffin" for shad, Lipcius said. "The reason that they got hit hard is because that's when they are spawning. They've migrated upriver to the tributaries, and that's where the sediment and river flow hit the hardest. And so, boom, it just washed out the larvae."
Maryland banned Bay shad fishing in 1980, the Potomac River was closed in 1982 and Virginia shuttered its portion of the Bay in 1994. Today, the shad population remains at historic lows in the Bay region and throughout its East Coast range, hovering around 1% of its late-1800s abundance, scientists say.
The drastic reduction in shad was also a sharp blow to the Bay's aquatic life. The fish had served as a vital link in its food chain.
Small and unseen losses
In the wake of Tropical Storm Agnes, scientists who often didn't know how they were going to finance their work were nonetheless quick on the scene, trying to quantify and explain the environmental damage. That search continued for decades, yielding thousands of pages of research.
But some of the storm's consequences couldn't be measured with the tools available then or now. Like the loss of a girl's verdant playground.
Elizabeth Andrews still remembers the crayfish.
A winding path of yellow pavers, which the 10-year-old version of herself called the Yellow Brick Road, led down a hill from her family's house in Fairfax County, VA. At the bottom flowed a little stream, a tributary of Accotink Creek, that hummed with enough life to sustain a young girl's imagination.
"It was a beautiful natural setting to grow up in," Andrews recalled. "We played down in the lower part of the yard, which was all woods all the time. And there were crayfish, and there were ducks that came all the time to eat the crayfish."
During Agnes, the trickle behind her house morphed into a roar, carrying away any-thing unlucky enough to get in its way. When the flood finally receded, the fence along the the yard was strewn with trash.
"That was remarkable to me because I didn't think there was much trash in the area," Andrews recalled. "And the whole lower yard, of course, was covered with sediment. It was a mess and drowned out plants."
Andrews' love of nature spilled over into her professional life. She worked for a time as head of the environmental section of the Virginia Office of the Attorney General and currently oversees the Virginia Coastal Policy Center at the William & Mary Law School.
Agnes shook her 10-year-old world. But the real disaster came afterward, she said.
The county brought in a bulldozer to straighten the stream and festooned its formerly green banks with ugly chunks of concrete, ostensibly to ward off erosion during future storms, she said.
The ducks and crayfish never returned. The magic was gone.
Jeremy Cox is a Bay Journal staff writer based in Maryland. You can reach him at jcox@bayjournal.com. This article first appeared in the June 2022 issue of the Bay Journal and was distributed by the Bay Journal News Service.
A post-Agnes aerial view of Cartersville, VA, on the James River about 25 miles from Richmond. The flood destroyed the Route 45 Cartersville Bridge, built in 1884, carrying away its four center spans. The two shoreside spans of the bridge still stand beside a new bridge and are preserved as historical sites. (Library of Virginia, via Flickr Commons)