After Superstorm Sandy, the federal government initiated the Rebuild by Design (RBD) competition aiming to create model, innovative programs for making communities flood-resilient. The Hoboken area became the beneficiary of this program, being one of just ten sites selected in the northeast United States. The mostly Dutch-based OMA Team developed a program entitled “Resist Delay Store Discharge” for Hoboken and small portions of Jersey City and Weehawken, now called Hudson River Rebuild by Design.
The Hudson River Rebuild by Design program, initially designed to be comprehensive, is currently focused on the “Resist” strategy, comprised of a series of floodwalls, revetments and deployable barriers to protect against future surges. The cost of building these structures is estimated to exceed the $230 million HUD grant awarded for this program now being administered by the New Jersey Department of Environmental Protection (NJDEP). The surges that the “Resist” structures are designed to prevent, however, are uncommon events. At a July 12, 2016 presentation, Dr. Alan Blumberg of Stevens Institute of Technology stated that a Sandy-type surge has a likelihood of occurring once every 260 years. The “resist” structures are designed to have a life of perhaps 100 years assuming the local government can provide for annual maintenance cost estimated to be $1.4 to $2.4 million. Perhaps more important, the flooding that regularly occurs in Hoboken is the result of a major rainfall events, not surges. The floodwalls and other barriers will do nothing to protect Hoboken area residents from this type of flooding.
Fortunately, the City of Hoboken has been addressing other flood prevention strategies apart from the Rebuild by Design project. These programs may actually provide the key to making Hoboken and other urban communities more flood-resilient and also could serve as a more cost-effective model. In December 2013, the City of Hoboken amended its flood ordinance and zoning code to ensure that new construction is built to a standard to withstand future flooding. These codes require a combination of wet and dry floodproofing below what is called the Design Flood Elevation so that the new buildings will be resistant to flood damage. The wet floodproofing would actually allow the water to come into a building and then leave when waters recede without causing significant damage. This conforms to the Dutch concept of “learning to live with water.” The use of concrete, ceramic tile, brick and other materials resistant to water damage meet wet floodproofing requirements.
Design Flood Elevation (DFE) is the base flood elevation associated with a flood that has a 1% probability of being equaled or exceeded in a given year plus the freeboard which is a margin of safety added to account for waves, miscalculations or environmental changes. In the Hoboken ordinance, the freeboard for residential structures is 1 foot in the A flood zone and 2 feet in the V coastal high hazard zone.
Floodproofing buildings provides protection against future flooding events — both major rainfalls as well as a Sandy-type surge. Dry floodproofing, which is by far the more costly alternative, would involve designing the building below DFE to keep floodwaters out and must be constructed to resist the hydrostatic pressure that would be exerted outside the structure by rising waters.
Both types of floodproofing involve raising heating, electrical and other mechanical systems above the DFE. Where this is not possible, such as an elevator on the ground floor, there could be a protective barrier that would be deployed if a flooding event is anticipated.
After securing a grant from the New Jersey Department of Community Affairs, the City hired the firm of Princeton Hydro to work with City of Hoboken staff to develop Resilient Buildings Design Guidelines which was published in October 2015. This report details how residential and commercial buildings can be floodproofed in accordance with FEMA standards. Case studies are provided on existing buildings that were retrofitted with floodproofing measures appropriate for that site. By undertaking these measures, the building residents were able to realize substantial reductions in flood insurance payments.
The report includes recommendations to preserve much of the ground floor features that help to maintain a lively streetscape that exists throughout much of Hoboken. Non-residential uses such as commercial offices and retail spaces are permitted below DFE and can be dry floodproofed. Parking and storage are also permitted below the DFE which poses the risk of blank walls at street level.