Hydrography

What the heck is Hydrography?


This past week we celebrated "world hydrography day" so I thought I would muse on this little known science's relevance to the American War for Independence. We will start with the hydrography definition: The science which deals with the measurement, and description of the physical features of the oceans, lakes, rivers, seas, and their adjoining coastal areas, with particular relevance to their use for navigational purposes. Although the formal science of hydrography was not established until the latter part of the 18th century (by the French), assessments of waterways were essential to the safety of navigation for many centuries prior, particularly beginning with the age of exploration. Throughout the American Revolution, those watermen who had intimate knowledge of the coastlines, rivers, and estuaries were critical to both sides, but especially the British, who depended on the Royal Navy for its strategic advantage.

A 1571 pre-Mercator nautical chart from Portuguese cartographer
Fernao Vaz Dourado

Knowledge of the waterways and shorelines around Boston, New York, Philadelphia, Wilmington, and Charleston played a critical role for ships of war, merchantmen, smugglers, and privateers. This held true especially for the rebels, whose use of small craft and longboats was often their only counter to the wide array of British ships. Local ferrymen, fishermen, and pilots played a pivotal role and both sides vied for their services and loyalty. Failure to understand the features above and below the water, as well as the local tides, often led to disasters, large and small. In ancient (and perhaps not so ancient) times, mariners called on Neptune, the god of the sea for assistance where knowledge of the tide and shoals failed them. Here are some tales of Neptune's influence on the struggle for independence...


The First Affair


The grounding of a ship in the run-up to the American Revolution is a prime example of hydrography's impact. The so-called Gaspee Affair occurred on June 9, 1772. The HMS Gaspee, a British customs ship, ran aground in Rhode Island and a Sons of Liberty group attacked and set fire to the ship. The British Government threatened to send the American perpetrators for trial in England, but no arrests were made. However their threat to send Americans to trial in England sparked alarmed protests in the colonies who were informed of the affair by the Committees of Correspondence. The establishment of the permanent Committees of Correspondence led to the founding of the First Continental Congress and eventually the Declaration of Independence.

Grounding and burning of the Gaspee - prelude to war

Gloucester


Neptune works both ways - he rarely takes sides. The Battle of Gloucester provides an example. It was a skirmish fought early in the American Revolutionary War (August 8 or 9, 1775) at Gloucester, Massachusetts. Royal Navy Captain John Linzee, commanding sloop-of-war HMS Falcon, spotted two schooners returning from the West Indies. After capturing one schooner, Linzee chased the second  (American)  into Gloucester Harbor, where it grounded. Linzee sent sailors out to seize the prize. However, the townspeople called out their militia, who captured the British seamen sent to seize the grounded vessel. The militia recovered the ship as well. Local knowledge of the waters around Boston provided an invaluable edge to the New Englanders who faced off against the powerful land and naval forces throughout that seminal year.

Massachusetts coastline

Separate from this incident, Gloucester is famous for providing the name of the legendary regiment of Marblehead sailors, whose knowledge and skill in navigating coasts and riverways played a pivotal role in rescuing the Continental Army from destruction and enabling Washington's Christmas night Delaware crossing that led to a stunning blow for freedom at Trenton.

Marblehead sailors skill enabled Washington on several occasions
and helped save the revolution

HMS Somerset vs Neptune

The HMS Somerset, began its service in the American Revolution by shelling Charlestown in 1775. Somerset had great success working in estuary, bays, and rivers. It was the flagship headquarters at Bunker (Breed's) Hill.

Knowledge of waterways was critical even for large ships of war

Somerset was involved in another brief but important incident during the war, the Battle of Chelsea Creek. On the night of 27 May 1775, the armed schooner, HMS Diana ran aground in Chelsea Creek while attempting to keep Americans from driving British livestock from Noddle's Island in Boston Harbor. The American rebels set fire to the ship. HMS Somerset's tender, Britannia was able to rescue Diana's crew. Later, it took part in the ferocious river fighting at Fort Mifflin near Philadelphia.

HMS Somerset

The battle for Fort Mifflin itself involved ships and boats negotiating the treacherous waters of the lower Chesapeake River. A desperate and long fought siege involving land and naval forces utilizing the elements and geography to advantage. The Somerset took part in the latter phase, bombarding the fort from far offshore. But other small ships and craft negotiated dangerous waters in the ebb and flow of savage combat that lasted weeks. To deny the British the use of two nearby islands, the Americans broke the riverside dikes. This act forced the British to build their batteries on top of the dikes and to labor in knee-deep water. As an example of the difficulties involved, the British lost an 8-inch howitzer and a soldier drowned when the craft carrying the gun sank in the Schuylkill. While bombarding Fort Mifflin, the Augusta and Merlin went aground. High tide came that evening, but contrary winds prevented sufficient depth for the ships to be freed. On October 23, 1777, the American forts concentrated their fire on the two stricken ships. HMS Isis worked its way alongside the stranded sixty-four in a rescue attempt. British accounts claimed that American gunnery did only slight damage but that flaming wads from the ships' guns caused Augusta to catch fire. At mid-day, the Augusta blew up in a tremendous blast that broke windows in Philadelphia. According to one eyewitness, 60 sailors, a lieutenant, and the ship's chaplain died while struggling in the water. The loud explosion was heard nearly 30 miles away in Trappe, Pennsylvania. After the destruction of the Augusta the crew of the Merlin set their ship on fire and abandoned ship.

British bombard Fort Mifflin

But Neptune's favor for Somerset ended when she ran aground off of Provincetown in 1778. Over 100 of her men were taken prisoner by angry locals who forced them to walk back to Boston, a distance of over 125 miles! The wreck of the Somerset revealed itself in those waters on themselves after a storm in 1886, and again in January of 2008.

Knowledge of the tides and shoals was critical in navigation around New York

New York, New York

When the British drove the Continental Army from New York City in 1776, the knowledge and understanding of the waterways and islands became essential to the British. Although they found no lack of sympathizers with knowledge of the waters, the Americans had their share. And the farther the British fared from the "safe zone" of New York Island (Manhattan) and Long Island, the more tenuous the situation. Thwarting an attempt at naval envelopment in 1776, the rough shoreline and waters of the Bronx forced General Howe to try landing further north near Pelham. This gave the Americans time to shift forces to protect the Continental Army and his line of communication.

The British landed at Pelham after the rocky shoals near
Throg's Neck proved unmanageable

The coves along the north shore of Long Island provided rebels the ability to slip boats in and out without (usually) risking detection. This enabled one of George Washington's more famous spy rings to pass intelligence across the Long Island Sound to American controlled Connecticut (where knowledge of the cost proved equally important). During the time of the war for independence, the great Sandy Hook was more than the peninsula we see extending from the Jersey shore today. The "hook" continued on across the mouth of the harbor as a massive sandbar that prevented ships of the line and frigates from passing in or out of the lower New York Bay except at high tide. This limited British options when needing to put ships to sea in a hurry. Later in the war, a French fleet gave up the notion of an attack on New York for the same reason.

British Navy in New York Harbor had to wait for the tide to rise
 before heading out to sea

The Carolinas  


In the Cape Fear area near Wilmington, North Carolina, superior knowledge of the coastal and inland waterways enabled the rebels to prevent reinforcements by sea and kept the critical state in American hands from February 1777 until a second invasion force of British troops arrived in 1780. Then began a prolonged guerrilla type war along the treacherous Cape Fear River.  British warships patrolled, while blockade runners attempted to smuggle invaluable supplies. Both sides depended on local knowledge of the waterways to achieve success.

In the savage guerrilla war along North Carolina's coast,
both sides depended on knowledge of the waterways

William Moultrie at
Sullivan's Island

In neighboring South Carolina, local knowledge of the waterways and swamps in the low country also played a huge role in the struggle. The partisans along the coastal rivers proved a constant thorn in the side of the British who needed two attempts to take the port of Charleston. In the first attempt in 1776, famed South Carolinian William Moultrie's canny defense, and the geography of the islands and waters, held off a large British force of warships and soldiers. A key to his success was the use of Palmetto logs for the fort. The palmetto is very porous (spongy) and each time the British would fire a cannon, the ball would get stuck in the fort and not explode. If it did explode fort's the sand walls would fall and smother the fire. Confused by the fact that the fort was not burning, the British moved in closer. Bad idea. Three of his majesty's ships ran aground on a sandbar which is now the location of Fort Sumter. There they became sitting ducks for patriots. Francis Marion, who would become famous later as the “Swamp Fox," ordered the fort's guns to be turned on those ships. The British managed to save two of the ships but a third was lost.

British naval map of Sullivan Island defenses