Storm surge barriers The New England experience

Although dwarfed in scale by the European barriers, three New England barriers constructed during the 1960s have some design features and operating characteristics that might be relevant to the New York metropolitan region. Barriers across open waterways exist at three locations: Stamford CT, Providence RI and New Bedford MA. The construction of hurricane-flood protection for the region was authorized by Congress in the Flood Control Act of 5 July 1958 (Public Law 85-500, 85th Congress). The settings are quite different in these three locations, and three different types of barriers were constructed (Wiegel, 1993; Bowman et al, 2005).

Stamford, Connecticut

In Stamford CT, the 1938 Long Island Express hurricane surge peaked at approximately 4 m. Between 1965-1968, a hurricane barrier was built across East Branch, above Stamford Harbor, at a cost then of US$14.4 million (see

Figure 9.13 Stamford CT hurricane barrier in a partially closed position

Source: Courtesy of Richard C. Carlson, New England District of Corps of Engineers, Department of the Army.

Figure 9.13). At the bottom of the opening, resting on a sill 4.3 m deep, is a flap gate — a hollow barrier structure about 30 m wide and 11 m high. Triggered by a storm surge threshold of 2 m, hydraulic arms raise the gate to the surface, taking 20 minutes to close. The interior of the gate can be pumped out so that the gate is able to float during maintenance operations.

Providence, Rhode Island

The Providence area has a history of storm flooding dating back to 1635. In more recent times, Providence was also hit by the Long Island Express (hurricane) in September 1938, with surges cresting at 5 m, leaving in its wake 600 dead and causing US$400 million damage. Then Hurricane Carol roared by on 31 September 1954, creating another 5 m surge, killing a total of 60 persons and causing US$300 million in damage.

After engineering and economic studies were completed in the late 1950s, a hurricane barrier was built across the 300 m entrance to Providence Harbor between 1961 and 1966 at a cost then of US$15 million. Seawalls 3-5 m high extend out from the ends of the barrier 250 m in one direction and 430 m in the other. A view of the Providence barrier (horizontal axis Tainter gate design) is shown in Figure 9.14.

Storm Surge Barriers

Figure 9.14 Horizontal axis Tainter gates built across Providence RI Harbor

Source: Douglas Hill.

Figure 9.14 Horizontal axis Tainter gates built across Providence RI Harbor

Source: Douglas Hill.

New Bedford, Massachusetts

The 1938 hurricane reached a flood level of 4 m at New Bedford. The hurricane barrier (not shown) separating New Bedford Harbor from Buzzards Bay was built from 1962-1966 at a cost then of US$18.6 million. Protecting 560 hectares (1400 acres), the barrier at New Bedford spans the 1500 m mouth of the harbor between New Bedford and Fairhaven MA. The 7 m seawall consists of packed clay core faced with large boulders, with a 50 m opening toward its eastern end. The opening consists of a reinforced concrete structure with two opposing steel Tainter vertical axis sector gates, each with a radius of 30 m, which can rotate to close the opening. The 20 m high sector gates weigh 440 tons, and rest on a concrete sill 13 m below MSL. There is no overhead restriction, and the New Bedford fishing fleet and pleasure craft routinely pass through the opening.

Since its construction, the New Bedford barrier has protected the harbor from many storm surges, including the 2.5 m surge of Hurricane Bob (August 1991) and the 2 m surge from an unnamed coastal storm in January 1997.

According to the New England District, US Army Corps of Engineers, none of the three New England harbors has experienced sedimentation problems attributable to the presence of the gates nor have any related dredging projects been necessary. A small amount of dredging was needed at the Stamford barrier in the mid-1990s to remove unrelated sediment deposits.

Was this article helpful?

0 0

Post a comment