... and the Swash Defense Dam 1881-1891
By Sandy Jackson
[Originally published in the November, 1995 – FPHPS Newsletter]
In 1870 the Corps of Engineers made a postwar survey of the Cape Fear River under Gen. J. H. Simpson.
The results of Simpson’s survey supported closing New Inlet, south of Fort Fisher, prior to any dredging in the river, since sand washed in the inlet would quickly refill the channel.
The River Improvements Act of July 11, 1870, appropriated funds for the Cape Fear improvements. General Simpson and Colonel Craighill of the US. Engineers devised a work at the New Inlet breeches to intercept the sand being washed into the river by the northeasterly gales and to then prevent the spilling of vast volumes of water through the breaches.
The works were intended to close the small inlets contiguous to the main inlet, thus forcing the water into the main channel of the Cape Fear River and scouring the channel to a capacity to admit vessels.
The first step undertaken to close the inlet was the erection of a 500-foot deflector jetty from Federal Point on the northern side of New Inlet, that followed a southwesterly line of shoals.
The work of closing the breaches between Smith [Bald Head Island] and Zeke’s Islands, was under the supervision of Maj. Walter Griswold and consisted of placing large, heavy wooden cribs, filled with stone, across the bottom.
The line of crib works started at the northernmost extremity of Smith Island and extended toward Zeke’s Island. For the greater part of its 1,200 feet length, the works were built upon the remains of a stone dike, constructed by Captain Daniel P. Woodbury in 1853. At the commencement of the work the water on the bar had diminished to the nominal depth of only 8 feet with a narrow channel.
During the 1870-1871 fiscal year the Corps of Engineers reported that a 607-foot section of the breakwater and superstructure had been completed across the most difficult breach that contained the deepest and strongest current. In addition to the construction of the breakwater, Griswold also began erecting sand fences and planting shrubbery and other vegetation on Zeke’s Island to prevent further erosion.
In 1873 the Corps reported that the closing of the breaches between Zeke’s and Smith’s Islands had been completed. The jetty extended 4,400 feet in length and was protected from the currents by sunken flats and thirty thousand sand bags.
Upon inspection it was found that sand had quickly accumulated, forming shoals around the jetty and further strengthening the structure. As a result of the building sand at the breakwater and sand fences, Zeke’s Island was being thoroughly merged into Smith’s Island beach and returning to its former shape before the 1761 storm that caused it to open.
Federal Point, however, and the outer point of Smith Island beach continued to wear. By 1877 Zeke’s Island had entirely lost its identity.
In 1872 the Corps made a proposal to completely close New Inlet, and a board of engineers met in Wilmington, to consider the idea. After careful review the board recommended closure of the inlet. Congress appropriated an additional one hundred thousand dollars for the continued task.
Work began on completely closing New Inlet in 1874 by placing an experimental cribwork along a line of shoals 1,700 feet long to the deep water of the channel. The cribwork consisted of a continuous line, or apron, of wooden mattresses-composed of logs and brushwood, loaded with stone, and sunk—that formed the foundation for a stone dam.
Each section of the mattress was 36 feet wide and 36 feet long and was floated out to its proper position and held in place by anchors. Having proceeded at a cautious pace, the Corps of Engineers halted the construction after two years of difficult work and the construction of only 500 feet for further consideration.
While reevaluation of the project was under way, it was decided to use any remaining funds to dredge the channels of the river at Horseshoe shoal, the Bald Head bar, and the “Logs,” a submerged cypress stand 7 miles below Wilmington to a depth of 12 feet.
When work on closing New Inlet continued in 1876 the project proved difficult because of the depth of the water and the amount of stone required to be piled on top of the wooden mattresses. The last mattress raft was sunk in June 1876, and it was estimated that 6,200 cubic yards of riprap stone would be required to be placed on the mattresses just to raise the dam to the low water mark.
The first load of stone was dumped on the dam in January 1877. The work continued year to year by piling small stone rip-rap on and over the foundation. As the dam lengthened, the amount of rip-rap needed increased as the current scoured the mud and sand from around the dam, increasing the depth of water.
By 1879, under direction of Asst. Eng. Henry Bacon, the dam had been built to the high water mark for its entire length of 5,300 feet; and one small middle section that had been left open for navigation was closed. More than 122,000 cubic yards of stone had been placed on the dam, and still more was needed to raise the dam to two feet above the high water.
At the suggestion of Bacon to Chief Engineer Craighill, heavy granite capstones were placed on top of the rock dam. The Corps successfully completed the closure of New Inlet in 1881.
Swash Defense Dam 1881-1891
While the Corps of Engineers was engaged in the closing of New Inlet, a storm in 1877 opened a breach between New Inlet and the closed Smith’s – Zeke’s Islands swash.
In order to prevent the purpose of the dam from being corrupted by the new opening, it was decided to close the breach by artificial means. The first attempt, made by Engineer Bacon in February 1881, proved to be of insufficient strength and collapsed.
A second attempt to build a sturdier structure followed during the spring and summer of 1881. During that effort over “400 heavy piles eight feet apart in two lines nine feet apart” were driven in a line across the breach. Sand quickly accumulated on the ocean side of the defense, reinforcing the structure.
A series of storms in August and September 1881, however, broke through the beach on the north side of the breakwater, flanking the defense and forcing its abandonment. In order to save the work, Bacon recommended that a line of defense be completed that extended from Zeke’s Island over the shoal water to reduce the tidal difference.
The Corps approved Bacon’s recommendations for the extended defense; without them the effectiveness of the New Inlet dam would have been severely compromised and a great deal of money and time expended with little more than a temporary improvement. A row of mattresses, 40 to 60 feet wide, was laid along the line earlier proposed. On top of the mattresses they piled stone, similar to the New Inlet dam, up to the high-water mark.
Storms again plagued the defense project and forced another swash to open just north of the other two and nearer New Inlet Dam. As a result, Bacon was forced to lengthen and modify the line of mattresses.
Contractors finally delivered the first load of stone to the works in December 1884 from a quarry on nearby Gander Hall plantation. The placement of the stone continued over the next several years, with minor delays caused by the occasional storm. By 1891 the Corps had completed the 12,800-foot Swash Defense Dam to its proper height and width.
The length of the upper section of the dam extended Battery Buchanan on Federal Point to Zeke’s Island, a distance of 5,300 feet. The continuation of the Swash defense dam from Zeke’s Island to Smith’s Island, 12,800 feet, made the entire closure just over 3 miles in length.
“The Rocks,” as the entire dam was eventually called, measured from 90 to 120 feet wide at the base, and for three-fourths of the line the average depth of the stone wall was 30 feet from the top of the dam. The Corps of Engineers topped the Rocks with concrete during the 1930s. The Rocks still separate the Cape Fear River from the ocean.
[Editor: Claude V. (Sandy) Jackson III included this article in a book he later published, ‘The Big Book of the Cape Fear River‘.
In the ‘The Big Book’, there are 22 pages detailing Historic Navigation and Dredging Projects on the lower Cape Fear including Snow’s Cut with descriptions, locations and pictures.]
Hartzer, Ronald B.
1984 “To Great and Useful Purpose; A History of the Wilmington District US. Army Corps of Engineers“. Wilmington: Privately printed.
Rayburn, Richard H.
1984 “One of the Finest Rivers in the South: Corps of Engineers Improvements on the Cape Fear Below Wilmington, 1870-1881.” Lower Cape Fear Historical Society, Inc. Bulletin 27, no. 3 (May): 1-6.
1985 “One of the Finest Rivers in the South: Corps of Engineers Improvements on the Cape Fear Below Wilmington, 1881-1919.” Lower Cape Fear Historical Society, Inc. Bulletin 28, no. 2 (February): 1-6.
1896 “Tales and Traditions of the Lower Cape Fear 1661-1896“. Wilmington: Lerin Brothers; Reprint, Spartanburg, S.C.: The Reprint Co., 1973.
US. Army Corps of Engineers
1870 “Annual Report of the Chief of Engineers to the Secretary of War.” Washington: US. Government Printing Office
Wilmington Star (Wilmington, NC.) 1873, 1876, 1877, 1886
Wilmington Weekly Star (Wilmington, NC.) 1872
‘The Rocks’ Arial View: Fort Fisher to Zeke’s Island to Bald Head
Google Maps: ‘The Rocks‘
Images: Zeke’s Island
Zeke’s Island – NC Coastal Reserve and National Estuarine Research Reserve
‘The Rocks’ 1761 – 1950: from the Bill Reaves Files
‘The Rocks’ in the News
November 1995 Newsletter (pdf) – Federal Point Historic Preservation Society