The reign of Rome’s Emperor Nero [A.D. 54–68], notorious for its cruelty and depravity, is perhaps best known for the fire that burned much of the empire’s capital, a fire which some claimed Nero had set himself. (Legend: “Nero fiddled as Rome burned”… Fact: Fiddles had yet to be invented.)

Tacitus, a historian of the time, discounts this accusation and grudgingly credits Nero for rebuilding the ravaged city. But before the reconstruction could begin, there were immense quantities of rubble to be carted away, resulting in the infilling of the marshes at Ostia on the estuary of the Tiber River, about 16 miles from the city.

As this example illustrates, wetlands have not always been as valued as they are today. This disregard was not limited to the Old World or ancient times. In Eastern North America, fully half of all the tidal and palustrine marshes extant at the time of European contact have been filled or drained by those who believed they knew better what to do with them.

The Tiber joins the Mediterranean Sea at Lido di Ostia, Rome’s principal port of entry during the Empire. Situated on a generally exposed coastline, Roman engineers built structures to protect the city from coastal erosion.

At the same time, the intensity of land use for agriculture and sprawl near the port in a time with poor land-based transportation meant that erosional losses to the river were immense.

In the lower estuary, sediments settled out and filled in channels to the detriment of navigation. Romans may have accomplished navigational dredging with something similar to “spoon and bag” dredges, where a boom with a scoop on its end was pushed through or swept across soft sediments until an attached bag was filled, then levered up and dumped in a waiting barge for disposal elsewhere.

Later technology, at least by the early 1600s, employed so-called “mud mills”: rotary treadwheels, powered first by men, then by horses, that ran a continuous chain of buckets traveling on an extendible boom that chewed away and excavated the bottom when pressed against it.

When Europeans of that time first visited the Chesapeake, they recognized the Bay as immeasurably valuable for shipping. For the vessels of that day it was immense, some claimed sufficient for all the navies of the world to ride comfortably at anchor.

The average vessel arriving, such as the Susan Constant of 1607, was 116 feet long, displacing 275 tons and drawing about 12 feet of water. With good seamanship, she could sail into almost any river port on the Chesapeake with depth to spare. She would be typical of many of the merchants who traded goods and took home tobacco over the next century.

Augustine Herrman’s 1670 survey around the Chesapeake, published in 1673, shows plantations springing up in hinterlands to the Patapsco. As settlements spread up the Bay and into tributaries, so did shipping. The Patapsco River, accessing parts of Maryland’s hilly interior, was only one of many, small decentralized trade waterways along the western and eastern shores that served hundreds of tobacco planters as an avenue for gathering and shipping their crops.

Baltimore was founded on the Patapsco in 1729. It was not the “city” of today, but was in fact, part of a cluster of other towns: Jones Town, Fells Point and, up the Patapsco, Elk Ridge Landing.

By 1735, navigators were using Walter Hoxton’s published chart and sailing directions, which showed full 3 fathoms (18 feet) in the entrance channel off White Rocks. Depths in the mouth of the Patapsco were just 2 fathoms, perhaps already showing the increased sedimentation from decades of erosion.

Although this was the age of tobacco in Maryland and Virginia, an economically driven shift to grain crops was beginning to occur as the nation’s needs, soil conditions and technology changed.

Until about 1812, the wheat grown in North America was largely an older variety called spelt (Triticum spelta), not today’s varieties of Triticum aestivum. With this older grain, seldom cultivated now, the chaff does not separate from the kernels as it is threshed. Although health food sources still extol its virtues, it was replaced by later wheat varieties with higher yields.

Wheat began to be imported around 1750, and the Maryland product shipped well, unlike others that spoiled en route. By 1796, Baltimore Harbor was burgeoning, and an observer counted 5,464 vessels arriving that year.

Meanwhile, Brazil, under Dom Pedro heir-apparent to King John VI who ruled the United Kingdom of Portugal and Brazil, sought and won its independence from Portugal in 1822. Emperor Pedro introduced several European items to Latin America, including white bread, which attained rapid social acceptance among those of refined habits.

Bob Keith in “Baltimore Harbor, a Pictorial History” publishes a freight bill dated 1838 shipping 132 barrels of “super flour” out of Baltimore to Rio de Janeiro on the brig, Ann. Could this super flour be one of the new wheat varieties replacing spelt? And, was it going to make Emperor Pedro’s white bread? The flow of Maryland wheat, or more fairly Chesapeake wheat, to South America had begun.

This flow was expedited by the development of coastal trading schooners, vessels rigged with fore and aft sails set on boom and gaff. These ships were of modest draft, enabling them to cross the bar or sill off White Rocks, which had limited the entry to Baltimore only to those vessels whose loaded drafts had a comfortable safety margin beneath the keel in depths of 15-18 feet.

Elsewhere, world shipping drafts were creeping upward: 17–18' in the 1830s, 21' 3" by 1850 and 26' 5" draft thereafter. In cross section, the hulls became more rectangular and boxy as the pressure for cargo capacity increased.

Much of this cargo was agriculture-based, and trade at Baltimore was running both ways with imports increasing as well as exports. In 1832, Baltimore received the nation’s first import of guano, the nitrogen-rich dropping of Peruvian cormorants nesting on the west coast of South America. Continual agriculture had led to decreased soil fertility, and guano proved to be an effective fertilizer.

The trade in this smelly amenity for agricultural soils increased to 60,000 tons, worth $3 million, by 1865. So did soil erosion, accentuated by increasingly widespread and heavy tillage.

This soil traveled downstream, and the pool behind the Patapsco River dam at Illchester was regularly being filled with sediment since at least the 1820s. A placer mining water cannon was periodically used to flush the accumulated sediment toward Baltimore Harbor.

Meanwhile, depths in the harbor were coming into conflict with increasing the drafts of the merchant fleet. In his book, Keith notes that John and Andrew Ellicott, who had built a wharf at Pratt and Light streets in Baltimore to handle their flour exports, used scoops and a horse-powered windlass to remove sediments and give ships the needed depth in 1783.

Maryland’s Colonial Assembly established port wardens to manage Baltimore Harbor and maintain navigation access that year, and levied a penny-a-ton tax on cargo entering or leaving the harbor. They raised this to two cents in 1788, and in 1790 employed a “mud machine,” with its equine treadmill or “horseway” winding in a drag bucket full of sediment. The addition, in 1827, of a steam engine to provide the horsepower, led Maryland’s senior Senator, Gen. Sam Smith, a Revolutionary War hero, to petition Congress for federal help in dredging Baltimore Harbor.

Chesapeake maritime interests had been severely chastened by British incursions during the War of 1812, and within a few decades, U.S. government surveyors were sent to the upper Bay to look at prospects for a naval base and to chart the Bay’s commercial harbors. This resulted in maps of both the landscape and bathymetry in the Patapsco and Patuxent rivers.

These detailed, hand-drafted charts were issued as navigation aids for mariners. The earliest charts from 1845 show the matrix of farmland, forest and villages that had arisen in the 175 years since Augustine Herrman’s 17th century map. Later charts illustrate how harbor and commercial interests were forced to accommodate each other.

Baltimore was ahead in the bid to be the country’s leading commercial harbor. It was close to steep gradient Piedmont streams that provided water power for mills: flour mills, and fertilizer mills, as well as iron and steel mills. The Chesapeake’s first steamboat was built in 1813, and just 14 years later, steam railroads began connecting Baltimore Harbor with the nation’s interior, rich in natural resources: coal, ores and timber. At the same time, markets for manufactured and imported goods sprang up, and railroad cars packed with oysters from the Chesapeake traveled all the way to the West Coast. By the mid-19th century, ship drafts were exceeding the depths available at the mouth of the Patapsco.

Capt. Henry Brewerton was put in charge of supervising the construction of Fort Carroll, located in an island in the Patapsco River, in the autumn of 1852. His Army engineers had for a year been using a dipper dredge, essentially a steam shovel scoop on a long arm, to haul up Patapsco sediments which were used to fill the interior of the fort. Later versions had two arms and two buckets and could raise 100 cubic yards an hour.

Promoted to lieutenant colonel, Brewerton went to work on the defenses of Baltimore during the Civil War, and his dipper dredges opened a 150-foot-wide passage out to the Bay.

The channel his men dug would later bear his name. Its initial six miles averaged 23 feet, but the controlling depth appears to have been 22 feet. The Brewerton Channel was opened in 1858, and later lengthened three miles so incoming vessels could sail up to Sevenfoot Knoll, aim for Hawkins Point and enter the Harbor.

Capt.William P. Craighill then became the Baltimore district engineer. Although his initial concern was fortifications, as the Civil War ended his energies went toward improving navigation. By picking a way among several shallow spots, drafts of 24 feet could be carried to Sevenfoot Knoll. Still, vessel depths continued to increase.

At one point, Keith points out that lighters (barges) had to offload cargo from open ocean vessels as much as 20 miles from the Inner Harbor. To meet expectations, a channel down to the Bay as well as out of it was deemed necessary. Studies of the currents indicated that a channel running straight south would be less likely to fill in.

Craighill served in Washington D.C. from 1866-1870 and his work was carried on by Gen. John Parke and Col. John Simpson, who named the channel after Craighill. When it opened in 1869, it was swept clear of obstructions for vessels drawing 21 feet.

By 1872, there was controversy over dredging: The oystermen complained that it destroyed their shellfish beds, and navigation interests claimed that oyster dredging across the Craighill collapsed shells and sediments into deeper water and “injured” the channel, for which Captain Craighill hoped there would be stringent laws and penalties. Oystermen could later lose their licenses for dredging within 500 feet of the channels.

Both channels were subsequently widened and deepened to 24 feet, using a new dredge design, the clam shell. It featured two opposing jaws that would be dropped into the sediments, which when lifting tension was applied, would close. Seven of these machines averaged 900 cubic yards a day, compared with 250 yards for the old dippers.

Baltimore celebrated the opening of the deepened channels in 1874, but ironically, in 1875, only 57 vessels drawing more than 18 feet used the channels. The channels appear on the navigation chart for 1877, in which year an aggregate 1,322,586 tons of cargo — an export value of $40 million — flowed through the harbor.

By the 1880s, dredging was being done entirely by contract firms, the Army no longer employing its own equipment. As the approach channels were deepened to 27 feet, engineering exceeded the Bay’s natural depths and the dredging operations began to encounter hard fossil clays from an ancient sea floor predating the Chesapeake. The dredging contractors wanted a 10 cent premium over their ordinary 10.75 cents a yard for this hard material. (Today, double digit dollars per yard are not unheard of.)

Still, Colonel Craighill pushed for increasingly wide and deep channels.

Making any significant “corner” is difficult for large ships. They tend to carry on their original heading even after the helm is put down, and thus swing wide, creating a hazard in narrow channels. Steering is also erratic when vessels get either too close to the bottom or side walls of channels. To solve this, a Cutoff Channel was dredged, also to 27 feet, minimizing the acute turn angles, and eliminating the need to ’round Sevenfoot Knoll. It appears on the navigation chart for 1880.

The same turning problem, incidentally, is claimed by modern mariners where the present mainstem Chesapeake channel bends (much less acutely) off Tolchester Beach on the Eastern Shore. The Eastern Extension of Brewerton channel was later dredged to speed vessels across the Bay to the Chesapeake and Delaware Canal approaches and Baltimore’s “second exit” to the sea. Baltimore, with front and back doors, is unique among U.S. ports.

In recent times, Baltimore’s place among the world’s ports has been in flux. The mix of products and packaging has vastly changed with much of the steel production shifted to outside the United States; the advent of containerized cargo; and the immense flux of foreign-made automobiles into North America.

Worldwide, economies of scale have been pushed to the limits with ever larger bulk and container cargo ships requiring ever deeper channels. Fewer and fewer East Coast ports can accommodate ships with these drafts and the competition to hold onto the business of the companies running these huge vessels is fierce.

Baltimore’s distance from the sea places her at a disadvantage, and some argue for the further deepening of her approaches so that very deep draft ocean carriers can get up the Bay and exercise the option of leaving through the C&D Canal. Only a thousand or so larger vessels have annually exercised that latter option in recent years.

Dredge spoils — the muds, silt, sand and contaminants from a long industrialized port — are euphemistically called “dredged materials” in the trade. Today, there is a large effort to put the better quality material to use stabilizing beaches or restoring the “footprints” of rapidly eroding Bay islands. But it is still both cheapest and fastest to simply dispose of them nearby in water deeper than is currently needed for navigation. This had been the source of the recent controversy over “Site 104” above the Chesapeake Bay Bridge and opposite Kent Island.

In the past, both dredged materials and disposal sites were arbitrarily designated. As in Roman times, it was considered beneficial to fill in marshes for some supposedly “higher use” and anything on the Bay bottom was simply considered gone or, at the very most, marked on charts as a “spoil area” to indicate to mariners that depths could be shallower than surrounding waters.

Starting in the 1950s, we gained an increasing awareness of the ecological services and habitat values supplied by wetlands and estuarine bottom communities, together with the understanding of how toxic materials interact to harm our living resources. There are billions of small organisms living in these environments: each a predator, processor or food to some other species, and ultimately fodder for the fish and crabs we value recreationally and commercially.

Soil erosion has overfertilized the Bay for generations, and old sediments exposed by dredge cutter heads are resuspended in the water and deposited in new places, releasing nutrients that would otherwise not be available for plankton growth. This is true even for disposal sites confined behind substantial dikes like Poplar and Hart-Miller Islands in the Upper Bay. The loads of nitrogen mobilized into Bay waters represent hundreds of thousands of pounds annually.

The disposal of dredged materials has become an important habitat issue which is today receiving rightful attention, but it’s only one side of the question. Humans occupying the watershed view themselves as having rights as well: rights of employment and commerce as well as rights to harvest.

These views inevitably conflict, and sorting them out is not easy. One approach is to look realistically at the economics.

Cargo moving on barges powered by tug or push boats is rapidly increasing and some believe that’s where Baltimore’s future success will lie.

If so, Past may not be Prologue in resolving these questions.

The author would like to thank Bob Blama of Baltimore District U.S. Army Corps of Engineers for giving access to two primary dredging references: John Huston’s 1970 book, Hydraulic Dredging, published by Cornell Maritime Press and Dr. Harold Kanarek’s 1977 book, Mid Atlantic Engineers: A history of the Baltimore District, published by the USACOE.