Retrospective: The Damage Caused by Hurricane Agnes

People still talk about Hurricane Agnes, though it was no longer a hurricane by the time it devastated the region 40 years ago this month. Even so, the massive tropical storm flooded millions of acres, carried away cars, destroyed homes, took lives—and forever changed North America’s greatest estuary, the Chesapeake Bay.

By: Tom Horton

When James Michener needed to conjure an epic storm for his 1978 novel about the Chesapeake Bay, he could draw on all of recorded history—not to mention his considerable imagination. But much of his material for the book’s fictitious “Great Chesapeake Hurricane of 1886” is believed to have come from an actual deluge unleashed 40 years ago this month.

In mid-June 1972, Washingtonians—distracted by the news of five burglars arrested for breaking into Democratic National Committee headquarters at the Watergate—might barely have noticed a weather brief about a modest hurricane named Agnes moving north from the Yucatán.

Indeed, by the time Agnes passed the Florida panhandle around June 20, it had been demoted to Tropical Storm Agnes, with winds never again to rise much above 45 miles an hour. Bearing down on the Chesapeake Bay on June 21, the storm had lost the tight, cyclonic integrity of powerful hurricanes: “a big mushy thing,” the Washington Post called it in its understated report on June 21.

In retrospect, “a perfect storm” would have been more apt. Beginning the afternoon of Wednesday, June 21, Agnes would thoroughly soak Maryland and Virginia, then unexpectedly hook back and stall, dropping unimagined rainfall across a region from Richmond to New York state, from West Virginia to New Jersey. That vast acreage overlapped much of the six-state, 64,000-square-mile watershed of the Chesapeake and its biggest tributaries, the Susquehanna, Potomac, and James rivers.

A wet winter and spring had saturated the ground throughout the region, so soils couldn’t absorb much of Agnes’s sodden fury. The result was “the most massive flooding in the history of the eastern United States,” according to the Federal Office of Emergency Preparedness. Agnes killed 122 people in its path—16 in the Washington area—and destroyed so many homes, bridges, and businesses that it remains one of the costliest storms in US history.

Ecologically, the impact was equally disastrous. The storm came unusually early in hurricane season, when the Chesapeake’s fish and aquatic plants were reproducing and at their most vulnerable. In the course of ten days, Agnes blasted the bay with as much polluting sediment, which washed down its tributaries, as the estuary normally receives in a quarter century. Some scientists think that this and other forces unleashed by the floods “tipped” North America’s greatest estuary into a widespread decline from which it has never completely recovered.

Flash flooding was the first punch. Rain pelted the Washington area, up to an inch an hour from Wednesday evening through Thursday, June 22. Few streams rose faster than DC’s Rock Creek. At the nearby National Zoo, director Theodore Reed leapt into the wolf enclosure to save a pup from drowning.

The volume of water cannonballing down Rock Creek was double that of any storm in recorded history. Motorists by the hundreds along Rock Creek Parkway, Canal Road, and the Whitehurst Freeway were forced to run or swim from cars or were trapped inside or swept to their deaths as water went from hubcap-deep to above windowsill level in minutes.

In Virginia, the Occoquan River jumped six feet above its dam and gouged a new channel around one end. Some 1,600 people, the bulk of them in Prince William County, were made homeless by the flooding, and thousands more evacuated as streams where toddlers usually splashed engulfed subdivisions. Most homeowners in 1972 had no flood insurance.

Outside Baltimore, a young mother in the upscale Ruxton suburb was blocked by floodwater roaring down the Jones Falls stream valley as she attempted to evacuate her three children, ages seven months to 3½ years. As she frantically tried to extricate them from their safety seats, the flood swept her away and filled the car. Rescuers found her later, still alive and huddled in the branches of a downstream tree. The children had drowned.

Greater floods were building as the storm cleared out on Friday, June 23. Agnes had dumped as much as 18 inches of rain in some places and a foot in many others, but the real story was its scope. Never in eastern North America had a storm rained so hard across so many thousands of square miles—enough, it was calculated, to add two feet of water across the 2,500-square-mile Chesapeake if the bay had been a reservoir, dammed at the mouth.

On Friday, June 23, reporting on Agnes for the Baltimore Sun, I got a look at what was headed for Washington as I crawled on hands and knees along a railroad bridge at Harpers Ferry, West Virginia, where the Shenandoah River normally slid peaceably, clear and shallow, into the Potomac. The bridge was vibrating hard enough that I didn’t feel confident to stand to snap a photo. A loaded coal train had been parked there in hopes that the weight would help anchor the bridge.

Where the two rivers collided thunderously in angry, brown foam, they created acres of standing waves several feet high. I had grown up among watermen on the Chesapeake and recall thinking that the best of their boats would be made matchsticks in this normally canoeable spot.

In Washington, the Potomac River crested Saturday, June 24—made chocolate with topsoil washed from a nearly 15,000-square-mile watershed and swollen to about twice its normal width. Refrigerators from Pennsylvania, pieces of turkey houses from West Virginia, caskets from a local mortician—the quantity and diversity of the debris moving downstream were remarkable. From the Watergate, the Washington Post noted, “residents sipped champagne and watched the show.”

The Potomac River swelled to twice its normal width, and much of DC’s waterfront flooded. Abandoned cars float in floodwaters near Baltimore. Photograph by Walter M. McCardell/Baltimore Sun.

Agnes's Deadly Path

June 14, 1972
Agnes forms over the Yucatán Peninsula.

June 19
By now upgraded to a hurricane, Agnes hits the Florida Panhandle and spawns a record number of 28 tornadoes over the next two days.

June 21
As Agnes, downgraded to a tropical storm, approaches the Chesapeake Bay, a weak cold front ahead of it dumps one to three inches of rain on the region, on top of an already unusually wet winter and spring. The storm moves into the Washington area, killing 16, flooding thousands of homes, knocking out pumping stations and leaving much of Fairfax County without drinking water. (Limited service was restored after 35 hours, full service after eight days.) About 16 inches of rain falls across the region in one day.

June 22
Agnes unexpectedly reverses course, setting up over the watersheds of the Potomac and Susquehanna rivers, dumping an average eight inches of rain across tens of thousands of square miles. The James River peaks at 70 times its normal flow, submerging a sixth of Richmond.

June 24
The Potomac peaks at 45 times its normal flow, the Susquehanna at 32 times. The Potomac reaches flood crest in DC—16.7 feet at Georgetown's Key Bridge—missing the 1936 record only because the crest arrived at low tide.

June 30
Tens days of riverflow from Agnes have "aged" the Chesapeake Bay by more than a decade a week, filling it with as much sediment as it normally gets in a quarter century. Flash flooding in the Baltimore area drowns three children in a car.

The Aftermath
C&O Canal National Historic Park is declared a major disaster area, with more than 200,000 trees uprooted and 66 miles of towpath severely damaged. In the Chesapeake, oysters, soft-shell clams, and underwater seagrass meadows experience massive mortalities. To this day, they've never rebounded to pre-Agnes levels.

Boats torn from moorings littered the shores for miles. Trees, roots and all, spun in the current. It would turn out that more than 200,000 trees had been ripped from the C&O Canal National Historic Park alone. With 66 miles of towpath severely damaged, the park would take years to repair.

Much of DC’s waterfront flooded, including parking lots at National Airport and the Kennedy Center. Only the coincidence of the Potomac’s crest with low tide prevented the river from breaking the flood of 1936’s record.

To the south, a sixth of Richmond—some 200 blocks of the city’s downtown—was inundated. Flows peaked in the James River on June 23 at 70 times normal. (They were 45 times normal in the Potomac.) Floodwater crested well above a seawall that had been constructed to protect the Virginia capital after the 1936 flood.

In Maryland, the Patapsco River ran 12 feet high down Ellicott City’s historic main street. A warehouse of barrels containing unknown chemicals and roofing products washed into one of Baltimore’s major drinking-water reservoirs, mobilizing a days long “fishing” expedition with every boat that Maryland’s Department of Natural Resources could muster.

Most attention was riveted, however—and Agnes’s awful power was most apparent—near the northern Maryland town of Conowingo. There, for only the second time since it was built in 1928, all 53 floodgates had been opened at the mammoth, 116-foot hydro dam plugging the Chesapeake’s mightiest river, the Susquehanna. I had seen water cascading through Conowingo’s floodgates during lesser storms, but now they disgorged into the river massive, graceless chunks—“projectile vomiting,” my notes from that week say.

In normal times, the 464-mile-long Susquehanna, draining lands as far away as Cooperstown, New York, sends almost as much freshwater to the Chesapeake as do the rest of the bay’s rivers combined. (The Potomac is a distant second.) Agnes struck harder in Pennsylvania’s sprawling Susquehanna basin than anywhere else—the whole state was a federal disaster area.

On Friday, June 23, a bulletin came from the dam’s operators: The river was reaching a point where Conowingo’s stability “cannot be controlled.” The dam was evacuated, with explosives installed to blow out a section if necessary. People emptied from the Maryland towns of Port Deposit and Havre de Grace, downstream from the mile-long lake of water held in check by Conowingo Dam.

Eventual flows peaked above anything seen before or since, but the dam, anchored in bedrock and thick enough to carry two lanes of US Route 1 nearly a mile across the river, held. Subsequent surveys showed that Agnes actually had moved the dam a quarter inch on one side. Route 1 was shut down for months while it was reanchored.

Expert observers at Conowingo had noted that the water thundering through the floodgates was darkening beyond the solid brown coming from upstream. That signified a rare occurrence: The river’s force was so great that it was scouring deep into long-buried, deoxygenated sediments that had been trapped behind Conowingo Dam for decades. The scour sent an estimated 20 million tons of smothering, polluting sediment hurtling downstream—in addition to another 14 million tons washed from upstream. No other storm has come close.

It was impossible to predict what the impact of such an event would be on the Chesapeake environment. Such a storm was statistically unlikely to recur for centuries. With no assurance of funding, scientists from Maryland and Virginia, along with Johns Hopkins, launched research cruises in the wake of Agnes, eventually making it the only tropical storm with its own 600-page book (The Effects of Tropical Storm Agnes on the Chesapeake Bay Estuarine System,Johns Hopkins Press, 1977).

The researchers knew that, among the world’s coastal ecosystems, the Chesapeake was almost uniquely sensitive to what occurred across the lands of its watershed. The reason was partly the sheer size of the watershed, more than 20 times the acreage of the bay it drained into. What’s more, there was surprisingly little water in the Chesapeake to dilute what its rivers sent down. The bay looks big—about a million feet long and up to a million feet wide—but it’s thin, with an average depth of about 22 feet.

This shallowness is key to the bay’s historic productivity, letting enough light penetrate to sustain hundreds of thousands of acres of rooted aquatic seagrass meadows. These lush grass beds are among the richest, most productive ecosystems on earth, on a par with coral reefs, mangroves, rainforests, and wetlands.

The grasses had been torn up by other hurricanes such as Hazel, Connie, and Diane in the 1950s and had come back quickly. Agnes, whose unprecedented clouds of sediment shut off vital light during the critical part of the growing season, devastated the grasses. Six years later, their baywide acreage was still down by nearly two-thirds. Only in the last decade or so have they rebounded in the upper Chesapeake and parts of the Potomac. But across the bay as a whole, they’ve never approached pre-Agnes levels.

Another Chesapeake icon that Agnes tipped over the edge was the oyster, whose once-extensive reefs were both a key habitat and a pollution filter for the estuary. Oysters were already in decline from overharvesting, but catches in the Potomac River alone still exceeded 600,000 bushels annually before Agnes struck.

It was an unlikely-sounding “pollutant,” the massive thrust of freshwater from the storm that wiped out many of the Potomac’s rich shellfish bottoms, according to A.C. Carpenter, executive secretary of the Potomac River Fisheries Commission. To live, oysters need about five parts salt per thousand parts water, Carpenter says. Freshwater is zero parts salt, ocean water about 32.

The Chesapeake, a mixture of ocean and riverflow, normally maintains tolerable salinities throughout the oysters’ range in the estuary. But Agnes’s torrents literally shoved the Atlantic Ocean back dozens of miles, apparently blocking any normal rebound of salt up the Potomac for several days. In colder weather, the oysters might have clamped their shells shut and effectively hibernated, but they couldn’t do that in the warmer June waters.

Police search Maryland’s Patapsco Valley State Park for three people swept away by the flood. The Patapsco River ran 12 feet high down Ellicott City’s historic main street. Photograph by Clarence B. Garrett/Baltimore Sun.

A year later, yet another legacy of Agnes emerged to claim most of the oysters that survived the 1972 onslaught. Large volumes of organic matter deposited by the floods along the Potomac and Chesapeake bottoms the previous year caused huge sags in vital aquatic oxygen as bacteria decomposed them. Despite extensive restoration of oyster bars, Carpenter says, Potomac harvests never again approached their levels before Agnes.

In addition, Agnes killed off an estimated 90 percent of the bay’s lucrative soft-shell clams. Perhaps already stressed by being at the southern limit of their species’ range here, the clams would rebound from place to place and time to time, but they never regained their prominence in watermen’s incomes.

Longtime Maryland Watermen’s Association president Larry Simns recalls that after riding out the winds and rain of Agnes in his workboat docked on the Eastern Shore, “I didn’t really see how this one storm could change my life.” But then, according to his memoir to be published later this year, Simns began watching “my bay turned to brown gravy . . . dead cows, drums of chemicals floating by.” The reports of shellfishing closures began piling up as health authorities acted to prevent sewage-contaminated clams and oysters from reaching market.

At some point, Simns writes, “I instinctively knew that my own best fishing days were in the past. . . . My primary job [as Watermen’s Association president] was going to be to defend the lives and livelihoods of watermen.”

He continues: “What we hoped was a ‘freak storm’ back then has become our daily reality today.”

Four decades after Agnes, despite attempts to restore it, the Chesapeake ecosystem has never regained the overall health it enjoyed before June 1972.

But we can’t lay all blame on any one storm. We might better argue that Agnes pulled the trigger, releasing insults that had been building across the bay’s watershed. Since the 1950s, fertilizer use on farmland had increased threefold. Animal farming in regions of the bay had become much more concentrated, resulting in an ever-increasing spreading of manure.

An excess of such nutrients is now recognized as the bay’s single biggest pollution problem. But why hadn’t it affected the body of water more before Agnes? Consider that just as the bay is hugely impacted by storm water carrying pollution off its watershed, in dry times a lot of that pollution remains stored in soil and groundwater.

And dry it had been, with river inflows to the Chesapeake below average every year from the mid-1950s until the early ’70s, including a period of such drought in the ’60s that some feared the Washington region would run out of drinking water. In effect, says J. Court Stevenson, a bay researcher with the University of Maryland, “we may have just been saving up all those pollutants to be flushed out into the bay.”

Stevenson’s work in the late 1970s led to understanding how runoff of nutrients and sediment was harming the seagrasses. And even without Agnes, the ’70s was a decade of relatively high runoff to the bay.

Add to all this a population in the Chesapeake watershed that’s on its way to doubling from 8 million in the 1950s to 17 million today, in the process dramatically increasing sewage flows. The population growth has also led to continued paving and development as well as to the clearing of forests and the filling of wetlands; forests and wetlands are both excellent buffers against polluted runoff. Then throw in oyster diseases that grew worse after Agnes (but may not be directly related to it), continued overfishing of some species of sea life, and warming bay temperatures that appear to be keeping some species of aquatic grasses scarce.

We can blame Agnes for a lot, but Maryland Watermen’s Association president Larry Simns laments that much of today’s grim reality can be traced to the manifold ways the burgeoning population continues to pollute.

Says Jerry Schubel, the top bay scientist who was an organizer of the research cruises immediately following Agnes: “Perhaps we focus too much on the big events and not enough on all the chronic stresses, the damage we do every day.”

Schubel, now head of the Aquarium of the Pacific in Long Beach, California, says he has tried to make the same point about the Gulf of Mexico, which suffers, he says, more from all the pollution flowing daily down the Mississippi River than from the BP oil spill in 2010.

The influx of freshwater to the Chesapeake from Agnes did have a salutary effect for humans: It virtually wiped out the bay’s normally robust population of stinging sea nettles and depressed their reproduction for two years afterward.

Agnes lent humbling perspective to a writer hired by the Baltimore Sun just before the storm blew in. Now, after 40 years of covering the Chesapeake, I suspect my biggest story happened the first few weeks on the job, when I was too green even to get a byline.

On a scientific level, Agnes taught me how “episodic” events—occurring on the order of centuries or longer—can be as critical to understanding nature as day-in, day-out observation. A scientist can measure sediment flowing to the bay through a whole career, for example, and have the illusion he knows how such flows worked—until an Agnes comes along.

And just how unusual a storm was Agnes? I’ve heard it called everything from a “hundred-year storm”—referring to a magnitude that has a 1-percent chance of occurring in any year—up to a 500-year storm. The real problem is that we don’t have the thousands of years of data needed to put such rare events as Agnes in proper perspective. In addition, the timing—June—may have been more unusual and damaging than the rainfall volumes.

Quite literally, we’ll never see another Agnes. The National Weather Service retired the name along with those of 75 of the nation’s other most costly and deadly storms.

Tom Horton (swanfall@gmail.com) began covering the Chesapeake Bay for the Baltimore Sun in May 1972, and the assignment lasted through 2006. He now writes columns for the monthly Bay Journal and teaches writing and environmental studies at Salisbury University. Horton is the author of eight books on the Chesapeake.

This article appears in the June 2012 issue of The Washingtonian.