Verrazano narrows storm surge barrier: A Dutch vision

A storm surge barrier closing of The Narrows to protect the New York and New Jersey metropolitan area from storm surges has been designed following a systematic design approach. Functions and requirements of the barrier have been determined. Important functions are retaining the storm surge, allowing ships to pass under normal conditions, and allowing sufficient tidal flow in the New York Harbor Bay. A large span of 860 ft., the Narrows is required to allow the biggest ships to pass; the sill level of this gate is 66 ft. below the mean water level. An additional 100,000 sq. ft. wet cross section is estimated to be sufficient for tidal flow. Several design options have been taken into account including sector gates, lifting gates, and flap gates. A combination of a large sliding sector gate with 18 lifting gates has been selected. The choice is based on experience with storm surge barriers in the Netherlands and combining favorable aspects of different types of barriers. Reliability and maintenance are important criteria for the selection. The location for the storm surge barrier is half a mile north of the Verrazano Bridge. This location has many advantages regarding depth of the channel, tie-in structures and length of the closure. The height of the gates is only slightly above the maximum water level of 28 ft. above mean water, allowing for wave overtopping during storm. The reduced height results in a cheaper construction. This is possible because of a large basin behind the barrier. Overtopping waves will add 2 ft. of water to the basin. Since barriers are closed early this limited rise is acceptable. The costs of the storm surge barrier are roughly estimated at US$ 6.5 billion. A significant reduction of costs is possible if the wet cross section can be reduced. This conceptual design of a storm surge barrier in the Verrazano Narrows is presented as a contribution to the debate how to deal with the increasing risks of a storm surge in New York, given the expected impact of climate change and realizing experience in the Netherlands has learned that investment in protection against floods is a good investment.

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