What is the Risk?

Many factors make New York City particularly vulnerable to major coastal storms and their secondary impacts. Based on the SLOSH modeling, storm surge inundation areas of the city have nearly 2.5 million city residents, a significant amount of extremely valuable real estate, and a vast network of critical, interconnected infrastructure.

Because New York City serves as a global financial center and the hub of a large, complex regional economy, damage from coastal storms has repercussions beyond the city’s borders. If a major coastal storm were to impact Northern New Jersey or Long Island, New York City’s close proximity makes it likely that the secondary consequences of those storms would also have an impact here.

The following sections discuss the consequences of major coastal storms upon New York City. Additional, related consequences are detailed in the risk sections of the following profiles:

Coastal storms can have a significant impact on the population of New York City. Based on population figures from the 2010 Census, nearly 2.5 million New York City residents live within a storm surge inundation area, putting them at increased risk.

New York City Residents in Storm Surge Inundation Areas from SLOSH Model

Storm Category

Estimated Population in Storm Surge Inundation Area

(2010 Census)

Category 1 318,000
Category 2 796,000*
Category 3 674,000*
Category 4 702,000*
Total

2,490,000

*Numbers are cumulative; Source: NYCEM GIS

As described in the What is the Hazard section (Expand Location & Expand Tropic Storms), worst-case inundation scenarios, modeled using the SLOSH output called Maximum Envelope of Water (MEOW), were used to create evacuation zones in the New York City Coastal Storm Plan (CSP). The evacuation zones were developed based upon a range of possible scenarios from the MEOWs.

Based on population figures from the 2010 Census, about 3 million New York City residents live in a Storm Surge Evacuation Zone and could be asked to evacuate during a coastal storm event.

New York City Residents in Evacuation Zones

Storm Surge Evacuation Zone Estimated Population in Evacuation Zone (2010 Census)
Zone 1 363,800
Zone 2 251,900
Zone 3 402,200
Zone 4 455,100
Zone 5 761,400
Zone 6 761,400
Total 3,000,000

Source: NYCEM GIS

New York City residents, particularly at-risk populations such as the elderly, people who are physically or mentally disabled, people with underlying health conditions, or others who require access or functional assistance, could be exposed to significant safety and health risks during a storm and after it has passed. Health risks could result from direct exposure to the impact of the storm -- people may drown in rising waters, get struck by flying debris and falling trees, or be electrocuted by fallen power lines.

People may also be forced to shelter in inadequate housing that lacks heat or hot water. They may be exposed to contaminated floodwaters, spoiled food, or mold. Further, they may experience the complete disruption of basic services. Rain, wind, and runoff may also contribute to high levels of turbidity (suspended pollutants) in local reservoirs, which interferes with the disinfection of drinking water.

Risk factors that increase people’s vulnerability to coastal storms include lack of mobility, language barriers, and lack of access to medical resources. Very elderly people are highly vulnerable because they often lack mobility or the means to evacuate an unsafe location. Elderly people are highly likely to be physically disabled or have pre-existing medical conditions that make evacuation more difficult, particularly in elevator buildings during utility outages. People who rely on life-sustaining equipment in their homes are at increased risk if coastal storms create power outages, and otherwise.

New York City has a large population of immigrants, including many people who do not speak fluent English. Language barriers may make it more difficult for these segments of the population to receive and understand storm and emergency warnings, and could inhibit their ability to translate these warnings into lifesaving action (See New York City's Vulnerability Assessment).

People with disabilities and other access and functional needs are also at increased risk because of their disproportional reliance on healthcare facilities. Hospitals, nursing homes, adult care facilities, and pharmacies may shut down or operate at reduced capacity during coastal storms. Patients and residents of these types of facilities are at risk during coastal storms due to power loss, especially people who rely upon life-support equipment, such as ventilators that operate with electricity. Approximately one-third of New York City’s hospitals and nursing homes are located in storm surge inundation areas. If backup generators and other types of essential equipment are located on lower floors, equipment might cease to operate if lower floors flood.

Coastal storms can strain the healthcare system as a whole. As facilities in inundation zones are evacuated or otherwise incapacitated, remaining operational facilities in the healthcare system become stressed. A storm’s impact may result in an increased number of patients seeking essential medical treatment at a limited number of increasingly overcrowded medical facilities with limited space. As a result, some patients may be unable to receive treatment. During or after a coastal storm, medical facilities and nursing homes find it particularly challenging to evacuate patients with critical ailments or injuries.

People who do not evacuate during a coastal storm and choose to shelter in place are also at increased risk for several reasons. Those sheltering in place may experience delayed responses from medical personnel due to lack of transportation, limited access to certain areas, non-functioning medical facilities, or high volumes of emergency calls. Power outages may disable systems that use electric pumps to distribute water to upper floors of high-rise buildings, stranding people without potable water or water for washing and flushing. Residents living in high-rise buildings also risk being stranded if they live on higher floors and lose the power that runs their elevators.

If storms knock out or damage essential utilities or building systems and if extremely hot or cold weather follows, people are exposed to greater risk by the lack of air conditioning or heat. If residents are stranded in flooded or damaged homes after the storm passes, they risk being exposed to secondary health hazards, such as contaminated drinking water or growth of toxic mold. If people are without power for an extended period after a storm, the health risks associated with food spoilage increase.

Following a major storm or other disaster, people who are directly, significantly affected may also experience or exacerbate mental health problems, such as post-traumatic stress disorder, anxiety, and mood disorders. These mental health impacts are most common in the months immediately following a storm, but can potentially last much longer depending upon the severity of the storm, the nature of their exposure, chronic stress factors related to the storm (such as prolonged displacement or power disruption), pre-existing mental health issues, and access to adequate care and assistance.

Buildings and infrastructure in New York City are vulnerable to significant damage during coastal storms. This section discusses the risk to New York City’s built environment from three perspectives:

  • High-rise and other buildings
  • Potential building losses due to winds from coastal storms
  • Infrastructure

Building Stock

The vulnerability of buildings to storm surge and storm damage in New York City varies according to the height of the building, its type of construction, the building’s age, and its location.

Low-rise buildings situated in inundation areas in New York City are more vulnerable to coastal-storm damage and destruction than mid-rise and high-rise buildings for several reasons. Because low-rise buildings have more floor area closer to the ground than other types, a larger proportion of these buildings will be damaged by the storm surge. Low-rise buildings are often built from light weight materials, so they are more susceptible to structural damage than high-rise buildings with steel, masonry, or concrete frames.

As buildings rise higher, their facades are more vulnerable to damage from extreme winds. Although predicting increase of wind speed associated with an increase in altitude, wind speed could be equivalent to speeds of one storm category stronger for every 30 stories of a building’s height. For older buildings not designed to modern standards, the higher wind speed associated with the higher floors of tall buildings could lead to broken windows and falling debris that puts people below and inside the building at risk. Despite containing proportionally less combustible material than other building types, high-rise buildings are vulnerable due to a different set of fire hazards, such as the difficulties associated with a complex vertical response and evacuation operations due to the building’s height.

The susceptibility of the built environment to flood damage depends upon the specific characteristics of the storm and the location of buildings. For example, buildings situated along the open coast are subject to higher wind speeds and also to the destructive force of wave action, which may cause more serious damage than would be suffered by buildings away from the coast that are subject only to stillwater flooding.

During Hurricane Sandy, which flooded nine percent of the city's building stock, much of the sustained building damage was caused by surge force and depth of inundation.  A significant proportion of the building damage during Hurricane Sandy was not structural; rather it was largely related to ground-floor and basement flooding where building and electrical systems were located. Building age is an important indicator of structural vulnerability. Older buildings are more vulnerable to coastal storm damage than newer buildings, because of the increased stringency of more recent building and zoning standards. During Hurricane Sandy, for example, structures built before New York City's 1961 Zoning Resolution and before implementation of the 1983 federal standards associated with Flood Insurance Rate Maps (FIRMs) from the Federal Emergency Management Agency (FEMA), suffered more severe damage than newer buildings. Many New York City Housing Authority (NYCHA) facilities that were built before implementation of the 1983 standards sustained significant damage from Hurricane Sandy.

Potential Building Losses due to Wind from Coastal Storms

Building losses under various potential storm scenarios are calculated using the HAZUS-MH (Multi-Hazard) hurricane module -- a wind model that does not calculate damage from storm surge. HAZUS-MH damage calculations are based on the effects of wind, wind-driven rain, and other wind-related hazards, such as projectile impacts. Although the module was developed specifically to assess the impact of hurricanes, HAZUS-MH can be applied to assess the potential impact of coastal storms that produce wind-related damage.

The HAZUS-MH hurricane module has five classifications of damage -- None, Minor, Moderate, Severe, and Destruction. Thus, wind-related structural damage is simplified into one of five basic categories. The table below outlines how these damage states apply to residential structures.

Residential Structures Below

Damage State for Residential Structures
Source: HAZUS-MH Hurricane Technical Manual
All of the coastal storm wind-damage estimates are based on a probabilistic analysis, because New York City has a limited record of deterministic events for the area over time. Probabilistic analysis in HAZUS-MH models building damage counts for seven discrete time intervals – in this case it models ten years, twenty years, and other intervals. Estimates of the number of New York City buildings that would be subject to damage from coastal storm winds over these time intervals are shown in the table below. For example, over a 20-year interval, 1,900 buildings in New York City could suffer damage due to winds from coastal storms. Note that these numbers are approximate, rounded to the nearest hundred.

HAZUS-MH Estimates: New York City Buildings Subject to Damage from Coastal Storm Wind

Intervals of Years Minor Moderate Severe Destruction Total Damaged % of Building Stock Damaged
10 0 0 0 0 0 0.0%
20 1,800 100 0 0 1,900 0.2%
50 8,300 800 100 0 9,200 0.9%
100 33,800 5,600 200 0 39,600 3.7%
200 95,100 20,800 900 100 116,900 10.9%
500 214,100 74,300 5,900 1,800 296,100 27.6%
1,000 278,200 139,000 22,600 8,700 448,500 41.8%
Source: NYCEM GIS

Following these assumptions and analytical structure, HAZUS-MH was used to calculate the dollar value of losses from wind damage from coastal storms affecting New York City over the same time intervals. The following table shows the results of these estimates, which includes the value of damage to buildings, the contents of buildings, inventory, and associated loss of income. For example, over a 20-year interval, cumulative economic losses from coastal storm wind damage in New York City are estimated at $36 million. Note that these values are approximate, calculated to the nearest thousand dollars.

HAZUS-MH Estimates: NYC Economic Losses due to Wind Damage from Coastal Storms

Intervals of  Years Building Damage ($) Contents Damage ($) Inventory Loss ($) Income Loss ($) Total ($)
10 0 0 0 0 0
20 33,705,000 2,118,000 0 403,000 36,226,000
50 975,795,000 61,113,000 2,400 61,911,000 1,098,821,400
100 3,716,611,000 297,158,000 510,000 311,354,000 4,325,633,000
200 9,819,929,000 1,001,845,000 3,796,000 1,060,439,000 11,886,009,000
500 26,742,564,000 4,430,584,000 31,180,000 3,471,425,000 34,675,753,000
1,000 46,676,010,000 12,114,116,000 67,990,000 6,164,189,000 62,022,305,000

Source: NYCEM GIS, 2007 values adjusted to 2019 values using the Bureau of Labor Statistics (BLS) Consumer Price Index (CPI) calculator.

Hurricane-level wind events occur infrequently in New York City. Another useful way to estimate the impact of wind damage from coastal storms in New York is to estimate the likely economic loss over a one-year (annualized) time period. The following table projects the annualized economic loss due to winds from coastal storms for each New York City borough.

HAZUS-MH Estimates: Annualized NYC Economic Losses due to Wind Damage from a Coastal Storm

Borough Building Damage ($) Contents Damage ($) Inventory Loss ($) Income Loss ($) Total ($)
Bronx 34,255,000 7,489,000 39,000 4,240,000 46,023,000
Kings 76,515,000 17,555,000 141,00 9,437,000 103,648,000
New York 46,020,000 7,498,000 39,000 5,770,000 59,327,000
Queens 77,924,000 18,990,000 105,000 8,933,000 105,953,000
Richmond 15,175,000 3,733,000 13,410 1,554,000 20,475,410
City Total 249,889,000 55,265,000 277,000 29,934,000 335,425,410

Source: NYCEM GIS, 2007 values adjusted to 2019 values using the Bureau of Labor Statistics (BLS) Consumer Price Index (CPI) calculator.

The following graphic maps this estimate of economic loss resulting from New York City buildings being damaged by winds from coastal storms. The level of economic loss is superimposed upon census tracts throughout the boroughs, showing where wind-damage losses are most highly concentrated.

HAZUS-MH Estimate: Dollar Losses to NYC Buildings due to Wind Damage from a Coastal Storm, by Census Tract

Source: NYCEM GIS, HAZUS, and Department of Finance

Much of New York City's aging transportation and utility infrastructure is also highly vulnerable to significant damage from coastal storms. Within the transportation sector, subway tunnels, subway stations, passenger car tunnels, and bus depots in low-lying, flood-prone areas are at particular risk. For example, during Hurricane Sandy the city suffered extensive flooding of subway, PATH, commuter train, and Amtrak tunnels; the Hugh Carey Brooklyn-Battery and Queens-Midtown vehicular tunnels. Disruptions in the commodity supply chain could result in shortages of liquid fuels throughout New York City. Physical damage or loss of power to key distribution terminals, as was experienced during Hurricane Sandy, is also a significant risk.

Vulnerable utilities include above-ground telecommunications and power-distribution infrastructure (power lines and electric substations) that are directly exposed to wind, flooding, falling trees, and flying debris. Underground power and telecommunications are less exposed, but are still subject to flooding in vulnerable locations. An inflow of saltwater can corrode and damage underground electric distribution equipment and transportation infrastructure.

The table below estimates that 35 percent of the total number of critical facilities and key assets in New York City are located within storm surge inundation areas for Categories 1 through 4 storms based on SLOSH modeling. The last column indicates the degree to which specific types of New York City facilities and assets are at risk from storm surge and severe damage during coastal storms.

As shown, all of the City's 26 power generation plants and 14 wastewater treatment plants are located in storm surge inundation areas, including thirteen wastewater treatment plants in the storm surge inundation area for a Category 1 storm.

Infrastructure and Critical Facilities Located within Storm Surge Inundation Areas

Asset Type SLOSH Cat 1 SLOSH Cat 2 SLOSH Cat 3 SLOSH Cat 4 In Storm Surge Inundation Area Not in Storm Surge Inundation Area Total % In Storm Surge Inundation Area
Airports (perimeter)* 1 1 0 0 2 0 2 100%
Nursing homes (FP) 12 21 13 11 57 115 172 33%
Hospitals (FP) 3 5 9 4 21 41 62 34%
Police stations (FP) 2 6 9 6 23 54 77 30%
Fire stations (FP) 13 23 13 18 67 159 226 30%
EMS stations (FP) 8 6 8 3 25 54 79 32%
Wastewater treatment plants (FP) 13 1 2 0 14 0 14 100%
Power plants (est. FP) 4 16 6 0 26 0 26 100%
Public school sites 50 146 129 116 441 938 1379 32%
Public school organizations 85 281 240 211 817 1662 2479 33%
Pre-K 83 170 168 171 592 1290 1882 31%
Private schools 25 67 76 64 232 591 823 28%
Colleges 3 9 9 10 31 92 123 25%
Ferry landings** 47 0 0 0 47 0 47 100%
Subway and PATH stations (point) 32 32 38 53 155 350 505 31%
Rail stations 6 4 2 4 16 27 42 36%
Cultural facilities (DCP)*** 1 6 2 1 10 27 37 27%
Bus depots 3 10 4 3 20 10 30 67%
Bridges**** N/A N/A N/A N/A 61 9 70 87%
Tunnels**** N/A N/A N/A N/A 4 0 4 100%
Major roads (mi)**** N/A N/A N/A N/A 479 408 887 54%
City total 391 804 728 675 3,140 5,827 8,966 35%

Source: NYCEM GIS

Note: Unless otherwise noted, a facility point was used to do a spatial calculation. This may result in some inaccuracies in category designation. Asset types with “FP” indicate that the actual facility footprint was used in calculation (FPs were estimated for power plants).

* Based on airport perimeter – significant surge impact only.

** Active New York City commuter/commercial/recreational ferry landings only (including Ellis and Liberty islands). All landings assumed to be in Category 1 Storm Surge Inundation Area.

*** Determination made by NYCEM and DCP on which assets to include.

**** Estimated only. Based on visual review of bridge/tunnel segments with ortho photo. Considered not in a zone if all New York City approaches are fully clear of inundation. Major roads do not include bridge/tunnel spans.

HAZARDOUS MATERIAL RELEASES DURING HURRICANE SANDY

During Hurricane Sandy, flood inundation levels reached many areas vulnerable to HAZMAT releases, including 20 percent of the City's fuel distribution facilities and approximately 5,500 industrial buildings. According to the 2013 City of New York report, A Stronger, More Resilient New York, 367 firms in the Community Right to Know (RTK) database were located within the area impacted by Sandy. Out of these 367 facilities, 263 reported no impacts from Hurricane Sandy. However, 46 facilities reported that they were severely affected, but reported no spills and showed no evidence of spills. Another 40 facilities closed or relocated. Of the remaining 18 facilities inspected by DEP, 11 reported spills but were cleaned prior to DEP inspections, and seven were completely washed out by the storm. In total, 11.4% of all facilities in DEP’s RTK database were affected during Sandy.

The EPA conducted tests at Newtown Creek and the Gowanus Canal after Hurricane Sandy to assess potential contamination. Samples taken from buildings that had been flooded by Newtown Creek indicated high levels of fecal coliform. Elevated levels of bacteria were found in samples taken from the ground floors of two buildings flooded by the Gowanus Canal. In addition, approximately 560 million gallons of untreated sewage mixed with storm water and seawater were released into local waterways, including the Gowanus Canal and Newtown Creek.

After Hurricane Sandy, evidence showed widespread oil contamination of residential buildings in the City’s coastal areas, including Coney Island in Brooklyn, Broad Channel and the Rockaways in Queens, and Midland Beach in Staten Island. Many residents living in the floodplain stored home heating oil in basements. According to the NYSDEC Spill Database, 1,620 spills occurred during Sandy that contained motor fuel and oil tanks to supply heating. Removing spilled oil and oil-contaminated water associated with this type of event requires a specialized response to achieve proper remediation.

For more details, see the section on Coastal Storms - How Does NYC Manage the Risk?

Coastal storms can have large impacts on natural areas and coastal ecosystems. Significant storms have the potential to erode and deform wetlands and cause barrier islands to narrow or split. Coastal storms can cause beach and dune erosion, wetland loss, and barrier island breaching that damages or destroys coastal habitats and disrupts migration patterns of terrestrial animals. The loss of natural storm barriers also exposes wooded areas and parks farther inland to the impacts of wind and storm surge.

Coastal storms can directly affect the health of the natural environment by contributing to the release of hazardous materials (HAZMAT) or causing overflow from sewers and wastewater treatment plants. Throughout the history of New York City, many industrial facilities have been built along or near the waterfront to facilitate maritime transportation. Even today, many of these low-lying areas are dominated by industrial use.

Flooding and coastal storms raise the risk of HAZMAT releases from these industrial sites, which could contaminate underground water and soil and create contaminated discharge into nearby bodies of water. Certain chemicals may be toxic to species of plants, animals, and invertebrates. Uncontained spills, especially those that impact surface water, can kill or injure plants, fish, and wildlife and cause damage to their habitats and food sources. The remediation of the natural environment after a toxic chemical release poses its own unique challenges and often involves lengthy, costly processes.

Large volumes of debris in local waterways can also be hazardous to local species. Large-scale changes in the population, distribution, and migrations of marine and aquatic species are possible over the long term.

In planning for the potential impacts of future coastal storms, planners and emergency managers must understand how climate change will affect the probability and severity of these storms in or near New York City. When considering the risk from coastal storms, impacts from three potential changes need to be considered – an increase in coastal storm surge as the sea level rises, an increase in extreme hurricane winds, and an increase in the frequency of the most intense storms.

Ocean surface temperatures are projected to increase as the global climate continues to warm, causing storms to intensify. It is unclear exactly how changes to all the climatic variables will affect the behavior of hurricanes in the future; however, climate scientists generally agree that the frequency of the most intense hurricanes (but not the frequency of hurricanes in general) could increase globally, particularly in the North Atlantic Basin.

Although uncertainty exists as to the exact nature of the change affecting coastal storm systems, scientists are fairly certain that the impacts of coastal storms will worsen in the future when combined with the impact of rises in sea level due to climate change. Climate change contributes to sea level rise due to several factors. As ocean water warms, it expands and increases in volume, causing sea levels to rise.

Global warming causes land glaciers and polar ice caps to melt at a faster rate, which increases the amount of water in the oceans. Since 1900, relative sea level has risen approximately 1.1 feet in New York City due to a combination of warming climate and local factors such as land subsidence (sinking).

The New York City Panel on Climate Change (NPCC) projected the degree of sea level rise in thirty year intervals. The chart below summarizes their findings for four intervals. As shown in the high end column under the decade of the 2050s, sea level around New York City could rise an additional 30 inches, or 2.5 feet.

NYC Sea Level Rise Projections

Baseline (2000–2004)

2020s 2050s 2080s 2100

Middle Range

High End Middle Range High End Middle Range High End Middle Range High End
Mean Sea Level Rise (SLR) 0 4 – 8 in. 10 in. 11 – 21 in. 30 in. 18 – 39 in. 58 in. 22 – 50 in. 75 in.
Coastal Flooding (Storm Surge with SLR) Annual chance of today's 100-year flood 1% 1.1 –1.4% 1.5% 1.6  –2.4% 3.6% 2 – 5.4% 12.7% - -
Flood heights associated with a 100-year flood 11.3 ft. 11.6 –12.0 ft. 12.1 ft. 12.2 –13.1 ft. 13.8 ft. 12.8 –14.6 ft. 16.1 ft - -

Source: NPCC

These rising sea levels around New York City would exacerbate the impact of coastal storms. More extensive damage would occur because a storm of equivalent magnitude would induce stronger storm surges from rising sea levels.

By the 2080s, extreme winds are more likely to increase in the North Atlantic Basin, affecting New York City, as shown in another chart summarizing the analysis of NPCC.

NYC Hurricane Wind Projections

Spatial Scale of Projection Direction of Change by the 2080s Likelihood
Extreme Hurricane Winds North Atlantic Basin Increase More Likely Than Not (>66% Probability)

Source: NPCC