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Tropical Storm Agnes only accelerated inevitable damage to the Chesapeake


The magnitude of the storm broke all existing records . . . it exploded with destructive fury into the body of the Chesapeake . . . the great bay itself was nearly destroyed. . . .

7+ -- from "Chesapeake," by James Michener

Michener's book is fictional, but the model for his "great storm of 1886," to which he devoted 10 pages of "Chesapeake," really happened 20 years ago this week. Many still blame this cataclysmic event for the ills the Chesapeake Bay continues to suffer. In fact, though the storm delivered a bullet to the bay's heart, we had been loading the gun and softening up the victim for many decades. The storm just pulled the trigger.

Called Agnes, it began off the coast of Yucatan, and bloomed into the season's first hurricane when it howled ashore in Florida June 19. When it reached the mid-Atlantic region June 22, Agnes had been downgraded to a mere tropical storm.

The punch of its winds was gone. But not of the rains it brought; and nothing like those had occurred in 185 years of recordkeeping. Worse, the deluge fell on lands already saturated from a wet winter.During the week that followed, human tragedy, not the bay, held center stage.

At Falls and Ruxton roads, the rampaging Jones Falls swept to their deaths a Baltimore couple's three children before they could be unstrapped from seat belts inside a car. Flash flooding worse than anything disaster experts anticipated would claim 21 lives in Maryland.

In its terrible way, Agnes reconnected millions of urban and suburban dwellers to nature. People were keenly reminded they didn't just live on a street, or in a town; but also in the drainage basin of a creek, in the valley of a river.

In metropolitan Baltimore, the storm dramatized how we had changed the very nature of those watersheds in a few decades before Agnes, stripping the vegetation that once absorbed and slowed the runoff of rainfall, paving it for roads and parking, and roofing it over with homes. It all channeled the water that fell with a destructive force never seen before.

A once-in-200-year-storm, the weather experts called Agnes, referring only to how much water fell; but never had that much rain fallen here on lands rendered so impervious to absorbing it by development.

On June 24 and 25, the bay's major rivers crested. From Conowingo, the 116-foot dam restraining a miles-long pool of water on the Susquehanna River above Havre de Grace came a bulletin: Despite the opening of all 53 floodgates, the dam was near a point at which "the stability of the dam cannot be controlled."

The James and Potomac both were gorged with 50 times or more their normal June flows. I recall crawling out on a railroad trestle where the Shenandoah River entered the Potomac at Harpers Ferry. A loaded coal train was parked there to hold the structure in place. It was vibrating so badly I could barely focus a camera, and standing waves where the rivers collided looked to be 6 feet high or better.

In the millenniums since melting glaciers formed the Chesapeake it had known many other Agneses, and even greater rains; but just as paving magnified the destructive force of rainfall in metropolitan areas, so had alterations to the bay's six-state drainage basin made this storm more poisonous than anything in history.

More than a third of the watershed's original forest was gone by 1972, millions of acres of a great, green sponge for rainfall, replaced mostly by plowed fields. A million acres of wetlands had performed similar functions, but now were drained or filled.

Consequently, Agnes carried bayward unheard of loads of choking, smothering silt. The Susquehanna in most whole years washes less than 1 million metric tons of sediment into the estuary. During 10 days of Agnes, the river carried an estimated 31 million tons.

Imagine you had been a scientist at the time, building a painstaking record of sediment polluting the bay; and imagine you and others had measured this for more than a century -- a longer data record than what supports most of our understanding of the natural world. Think how that scientific certainty would be shattered as a single catastrophic event geologically "aged the bay [i.e. filled it in]" by decades in a week.

It was not just the volume of sediment carried by Agnes -- fertilizers and pesticides, both pollutants of the bay, had doubled and tripled in use across the watershed's farms and suburban lawns in the two decades before Agnes. Once again, the "200-year" storm carried with it potential for damage that was simply unprecedented.

For all that, the bay in many respects proved surprisingly resilient. Its many varieties of fish, its blue crabs and its hard clams suffered "generally minor and temporary" impacts, according to an assessment in 1976 by the Chesapeake Research Consortium.

Oysters and soft clams suffered for a couple of years, but not beyond that (or at least, beyond that, the problems were not from Agnes). Sea nettle reproduction took a big hit, but returned full strength in a few years.

But a major habitat of the bay -- its huge meadows of underwater grass -- did crash dramatically after Agnes, as waters clouded by silt and super-fertilized algae blooms no longer let light penetrate sufficiently for their growth. Large increases in flows of human sewage to the bay had also begun to weaken the grasses by the time of Agnes. To this day the grasses -- refuge and food for a huge variety of bay creatures -- have not recovered.

We could blame it all on Agnes and say it was a freak of nature, beyond our control. But Agnes only speeded up what was inevitable, given the way we had altered the watershed.

If the entire decade preceding Agnes had not been dry, with historically low runoff of pollution from the land, the grasses might well have crashed before 1972. And if the disappearance had not come in 1972, it would have happened later. This did happen in some Eastern Shore rivers, which got little rain from Agnes and did not lose their grasses. After a major storm in 1975, their grasses went too.

We will likely never again see a rain so large as Agnes in our lifetimes. But if we do not begin restoring the bay's natural defenses against polluted runoff from the land -- its forests and wetlands; if we continue loading its rivers with too much silt and fertilizers, even smaller storms may prove just as deadly to the cause of restoring the Chesapeake.

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