Saving Flagler's Beach

Olsen Associates of Jacksonville, and the Army Corps of Engineers, did studies of Bald Head Island, North Carolina, and concluded that any renourishment would be “greatly enhanced” by installation of a “groin field” to help retain sand.

This groin project was written up in Shore and Beach, January 1998, by Paul Denison of Century/von Oesen Engineers, whose firm actually was the design/construction firm of record.

Due to the NC regulations on “hard” structures, Denison provided a design employing sand-filled, straight, “Longard” geotextile tubes in the lengths determined by Olsen's earlier analysis. Interestingly, these were deemed “experimental” by the state and allowed because the state accepted the notion that the deep Federal navigational channel adjacent to the island contributed significantly to the erosion.

Sixteen straight nine-foot diameter tubes were deployed in June 1996 (with a bedding mat with 3-foot diameter ballast tubes at each edge—a technique found in Holmberg’s original patents).

The tubes were placed in trenches dug into the new beach nourishment fill (Note: 600,000 Cubic Yards had been dredged and filled for this project). Of course, the fill and the groins survived for a few months, but by March, 1998, the Raleigh News and Observer reported that four of the groins were destroyed, and others were torn.

Wade Horne, 1998 City Manager of Bald Head Island, North Carolina, inspects the remains of one of 16 sand-filled geotextile groins palce on its western end after a design study by Olsen Associates and the U.S. Army Corps of Engineers. The Flagler County Turtle Patrol reports such torn bags have been found hazardous to sea turtles.

Though the article says that much of the sand remained, this does not take into account the additional 500,000 CY added after the 1996 fall hurricanes took most of the original sand (according to Denison, only 100,000 CY was lost in measurements immediately after the storms). The article also states that some of the damage to the tubes may have come from a contractor hired to dump sand on the beach—which means that even with the sand tubes the beach was already being renourished.

The side-effect for the island community was the 6% tax on rentals and oceanfront properties were asked to pay in additional taxes for beach nourishment, which the town pays out of pocket. Even in 1998, the town was wondering how it could keep this up.

Nonetheless, Olsen [the town’s Coastal Engineer] designed another groin field for Bald Head in 2005 (see Olsen’s website, www.olsen-associates.com ), after the newly deepened and relocated Cape Fear River channel hastened erosion there. Interestingly, remnants of the earlier bags were found after more renourishment sand was washed away.

The article by Denison, of course, claims some success. It concludes geotextile groins are a viable, economical method of groin emplacement even though damage can be expected.

Olsen used sand groins again at the south end of Amelia Island, Florida, and these were soon damaged and washed out. So for an extra $12 million, Olsen designed a two million CY renourishment with 1600-foot rock groins extending south of the island, with a 300' rock breakwater built off the beach north of it. Environmental groups fought this and eventually lopped all 100' off the groin.

Olsen said the structures would cut down the loss of sand and without them the beach fill would be gone in two years. The groin project was done late in 2004. Even with the rock groins, however, 250,000 CY of beach fill from the Nassau Sound dredging was dumped on the south end of the island only a year later.