New Jersey Flood Risks: Not Just Coastal
By: Kevin Paul, AIA, NCARB, LEED AP, CFM | Sr. Vice President and Private Sector Real Estate Discipline Director at H2M architects + engineers
Flooding and storm surges have become increasingly problematic for coastal communities in New Jersey. According to the New Jersey Department of Environmental Protection, over half a million acres of New Jersey land are highly vulnerable to coastal hazards, with nearly two-thirds of New Jersey’s coastline at high risk of coastal erosion and nearly all of the coast facing imminent sea level rise.
However, inland communities—even those located far outside federal flood zones—should not assume that they are insulated from flood risk. Riverine flooding is another dangerous form of flooding that can move quickly and leave destruction in its wake.
Riverine flooding is the result of a water channel overflowing into the floodplain. This can be caused by a downstream blockage or an overabundance of rain or snowfall draining from the watershed into the channel. The severity of a riverine flood is generally based on nearby terrain and the velocity of the moving water. Flash flooding is an even more severe subset of riverine flooding in which massive rainstorm deposits atop hills and mountains rapidly flow into the valleys below, transforming uprooted trees and other debris into dangerous projectiles along the way. Flash flooding is more common on the Pacific Coast due to the presence of mountains, but communities on the Atlantic Coast are not immune to the destruction these floods bring.
Thankfully, many of the flood mitigation measures that bolster coastal resiliency are easily applicable to structures within the riverine floodplain.
In 2021, Hurricane Ida hit the Atlantic Coast, inundating the City of Rahway, NJ, with floodwaters. Storm conditions caused the Robinson’s Branch of the Rahway River to overflow; paired with the area’s topography, this created the perfect conditions for destructive riverine flooding. Community facilities such as the Hamilton Stage at Union County Performing Arts Center filled with floodwater, damaging the facility interior and spurring toxic mold growth.
New flood mitigation measures for the Hamilton Stage incorporate dry flood-proofing technology. Dry flood-proofing involves insulating a structure to allow no more than four inches of water to enter within a 24-hour period. Flood-proof doors, for example, compress against the doorframe as rising floodwaters apply increasing pressure, creating a watertight seal. These doors also feature latches for manual activation, creating a seal without the required floodwater pressure.
For larger properties, horizontal passive flood barrier systems use the increasing hydrostatic pressure of floodwaters to automatically float barriers into position to create a watertight seal. As the water continues to rise, so too does the flood barrier; when the water recedes, the flood barrier follows suit by sinking back into place. Regardless of which dry flood-proofing systems are used, it is essential that they are capable of self-activating without electricity, mechanical assistance, or human intervention.
Conversely, wet flood-proofing allows a limited amount of water to enter the structure via vents and breakaway wall systems that direct floodwaters into areas more resilient to water damage. Rooms constructed out of concrete, masonry, porcelain, or any other material resistant to fungal and bacterial growth are ideal endpoints for wet flood-proofing systems. The benefit of allowing water into the structure is that it equalizes pressure on both sides, whereas dry flood-proofing systems are technically always at risk of buckling under one-sided hydrostatic pressure. However, wet flood-proofing is not feasible everywhere and may not work if certain spaces or areas cannot be elevated.
The specifics of any flood-proofing strategy depend on a wide range of factors, from building material to local elevation and topography. Other valuable strategies include elevating important spaces and equipment and reinforcing building foundations, which can face erosion even when outside the riverine floodplain. In areas with an elevated risk of flash flooding, property owners should create safe zones around their property by keeping trees and other potential hazards a safe distance away from the at-risk structures.
Experienced architects and civil engineers, particularly Certified Floodplain Managers, are ideal consultants for determining which flood mitigation strategies work best for any given facility. By tailoring mitigation plans to the specifics of the facility and the needs of its property owner, these experts can address a multitude of risk variables and provide peace of mind for river-adjacent communities.
To learn more about how H2M architects + engineers can help bolster your commercial real estate against storm damage, visit www.h2m.com, or email Kevin Paul at kpaul@h2m.com or Real Estate Market Director Michele Pincus, Esq., at mpincus@h2m.com.
About the Author
Kevin Paul, AIA, NCARB, LEED AP, CFM, is a Certified Floodplain Manager with over 40 years of design and construction experience in both residential and commercial fields. He directs the Private Sector Real Estate Discipline at H2M, where he manages and facilitates all phases of architectural and design projects from initial studies through construction administration. Focusing on commercial, industrial, institutional, retail, and residential projects in the private sector, Kevin is responsible for preliminary design, construction document preparation, budgeting, scheduling, planning, code analysis, and construction administration.
Prior to joining H2M, Kevin worked as a project architect in New York City and Long Island on a variety of projects for clients such as the New York City Department of Parks & Recreation, colleges and school districts, Metro North Railroad, and multi-family residential developers. In private practice for 25 years, he worked primarily on custom residential design and small commercial projects, including repairing and elevating storm-damaged homes on Long Island, as well as in Brooklyn and Staten Island for New York City’s Build It Back Program, in the wake of Superstorm Sandy.
Kevin is a member of the Association of State Floodplain Managers, the New York State Floodplain and Stormwater Managers Association, and the New Jersey Association of Floodplain Managers.
