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Climate Impacts in New York City: Sea Level Rise and Coastal Floods


The Rockaways, Queens

Map of projected flooding in the Rockaways for 2050
Figure 21: Projected flooding for 2050.
Source: J. Mendosa 2002
Map of projected flooding in the Rockaways for 2100
Figure 22: Projected flooding for 2100.
Source: J. Mendosa 2002

The detailed beach profile shows that a 100-year flood could have devastating effects on the region. The beach will not be sufficient protection from a surge created by such a powerful storm. Projections for 2050 and 2100 (Figures 21 and 22) imply that up to 3.5 meters of beach could be lost as a result of permanent inundation due to sea level rise, not counting beach erosion. This means that the region will receive less protection from the beach, in the event of a storm. According to Coch10, "wide beaches, high dunes, and stands of vegetation are the best defense against storm surge." With sea level rise, beaches will become much narrower, which will weaken the region's defense from storm surge. This is becoming even more of a pressing issue because new housing is being built to attract more people to the area.

In addition, the Rockaway region is home to Beach Channel High School, which is built on landfill. The Rockaways also houses another junior high school and a sewage treatment plant. When a severe flood comes into the area, the sewage treatment plant is forced to dump raw, untreated sewage into the waters that surround it. This poses a threat to the marine life in the waters, as well as to the many people who use the Rockaway beaches during the summer months for recreation and as a food source for fish (sport or subsistence fishing).

Photograph showing Rockaway Park Sewage Treatment Facility.
Figure 23: Rockaway Park Sewage Treatment Facility.
Source: M. McGraw

One possible way of dealing with the effects of sea level rise in the Rockaways for the short term is to step up the beach nourishment projects that have been going on since 1924 to fight coastal erosion. Depositing more sand on the beach will strengthen the defense that the beach provides against coastal flooding in spite of sea level rise. In the long-term, it is likely that sea walls will have to be constructed around built-up areas. The wetlands of Jamaica Bay, should also be protected as they act as a buffer against coastal storms for this region. This is necessary for protecting the local residential communities such as Broad Channel or Howard Beach. In addition, it is important to preserve such an important ecological resource.

In summary, this assessment has shown that the Rockaways will be vulnerable to the consequences of sea level rise. It is important that the NYC Department of Environmental Protection and The New York State Department of Conservation to take action on this issue before time runs out.

Photograph showing Sea wall  built on landfill.
Figure 24: Sea wall built on landfill. Source: M. McGraw 2002

Downtown Manhattan

Lower Manhattan has a population of approximately 6.3 million inhabitant. The income distribution ranges from $10,000-120,000/year, the residential property within Lower Manhattan may be relatively low, its commercial and federal sites certainly bring up its real estate value, making it one of the most expensive places in the United States to reside in. Although Manhattan has dealt with the flooding issue relatively well so far, it has a long way to go. Storm intensity and frequency is increasing, and while the rates are not tremendous, current trend models do show a projected increase of 27.6 cm/year

Photograph showing Battery Park sea wall. See text for discussion
Figure 25: Battery Park Sea Wall.
Source: M. Gonzales 2002

Figure 25 of the Battery Park sea wall displays the relatively low height between the water level and the highest point on the wall. Housing developments, parks and commercial real estate lie less than a quarter of a mile away from the sea wall, placing themselves at very high risk for flooding during coastal storms.

Figure 16 shows the recurrence curve, which was used during the study to calculate the impact of future storms in the area. It was concluded that not only would storm intensity increase in the future, but storm frequency as well. Simply stated, this means more damage for the Downtown Manhattan. The exact damage of future storms can not be accurately defined, strong storms can be expected in higher numbers in the near future, leaving a great deal of damage in their wake. The Nor'easter of 1972 reached NY in the second week of February, causing major flooding to coastal communities, such as Battery Park and lower Manhattan, it flooded JKF Airport, and caused power outages that led to the suspension of subway services for the duration of the storm. A storm of such an effect was only witnessed once during the 1970's, and although the 1980's did not see that many more, the 1990's brought about a high number of storms of similar intensity (e.g., Perfect Storm, 1992). A sea wall as low as the one depicted in the image above will be of little help when a severe storm like the Nor'easter of 1972 strikes again.

Photograph showing the Brooklyn Bridge. See text for discussion
Figure 26: Brooklyn Bridge.
Source: M. Gonzales 2002

Although the bridge in the picture is not directly at risk for flooding, it might be a susceptible to storm damage. Because of its low elevation, and its proximity to rivers and the Atlantic Ocean, water could inundate the public transportation system.

The map below highlights the entrances to the two major bridges connecting Manhattan with other boroughs. While the bridges themselves may not fall be victimized by the flooding, access to them could be severely impaired which would demobilize the city. This could result in major economic losses not only to the city, but to the world that depends on New York as a financial center.

It should be noted that within the study period chosen, a sea level rise trend was noted. Although the current trend is the most conservative of the 4 models analyzed in this study, it projected a flood height increase of 276 mm above the base level in the year 2100. What this shows is that sea level rise is continuously increasing and affecting areas close to the coast.

Contour Map of Lower Manhattan highlighting entrances to Manhattan. See text for discussion
Figure 27:Contour Map of Lower Manhattan.
Source: USGS 2000

Jamaica Bay, Queens

Even though no major hurricanes [or storms] have hit the Jamaica Bay area within the past five years, the probability of a hurricane causing significant damage is likely. For example, Hurricane Donna (1960), the Nor'easter of 1984, and the Perfect Storm (1991) all impacted this area over the last 50 years. Since this has not occurred in the past five years, we are probably due for some event soon. Past studies have indicated that the magnitude and frequency of hurricane activity might be on the increase with global warming and Nor'easter may be of increased magnitude as well11. This emphasizes the importance of early preparations.

Photograph of homes in Broad Channel. See text for discussion
Figure 28: Example of homes in Broad Channel.
Source: D. Alade, NASA GISS

Figure 9 in Case Study Sites, illustrates the disappearing wetlands in the Jamaica Bay Wildlife Refuge. These salt marshes serve as buffers against coastal flooding for the nearby communities on the mainland and the smaller Broad Channel Island. Figure 28 shows the houses on Broad Channel, built on stilts to protect against flooding. However, looking at the 2050 and 2100 GISS flood height projections, it is likely that these homes will be inundated with water. It is also possible that 3.5 m of marshland will be destroyed due to sea level rise. The degradation of the marsh will decrease the buffer zone between the mainland and the oceans storm surge, and an important wildlife habitat will be gone.

The coastal wetlands of Jamaica Bay continue to erode. This assessment has shown that the Jamaica Bay is susceptible to the consequences of sea level rise. It is up to the policy makers and city, state and federal agencies to meet the challenges of sea level change. The costs of not preparing are tremendous in terms of property damage, loss of infrastructure, and damage to the unique ecosystem of the bay.

Future Research

As far as future research is concerned, it is imperative that more studies be done like this, on a micro scale, on other coastal communities at risk from sea level change, such as Coney Island in Brooklyn, Orchard Beach and City Island in the Bronx, and certain parts of Long Island. In addition, scientists need to develop a better understanding of storm behavior in order to improve predictions of how storms will affect the region in the future. Finally, steps should be taken now to plan for sea level rise.

Additional research is needed to correlate coastal flood events, measured by tide gauges, with storm parameters such as central pressure, wind velocities and storm tracks. Higher resolution topographic data are needed, as are higher-resolution regional-scale climate and surge models. Finally, more work should be undertaken on socio-economic and development trends, linked to climate change projections.


The Impacts team would like to thank Dr. Vivien Gornitz for her dedication to our project and for accompanying us on field trips. We would also like to thank Dr. Cynthia Rosenzweig for making this team happen this summer. Thanks to Jeff Jonas for assisting us with the use of his Storm Tracks Table Program and to Mark Chandler for his Storm Tracks Map program.

In addition, Dr. Ellen Hartig gave generously of her time and knowledge to make our Jamaica Bay field trip rich and educational. Jose Mendoza was instrumental in creating our graphics. Spiros Papanikolaou assisted our team with the global positioning unit. Rich Goldberg was instrumental in providing historical and future projections of temperature, sea level rise and precipitation.

Other References

Brown, Lester. Rising Sea Level Forcing Evacuation of Island Country. November 15, 2001. Earth Policy Institute. 23 Feb 02.

Douglas, B. & Peltier, W. R. (2002) "The Puzzle of Global Sea-Level Rise." Physics Today, March 2002.

Gornitz, Vivien. Coastal Populations, Topography, and Sea Level Rise, GISS website

Gornitz, Vivien. Personal communication with Vivien Gornitz. July 24, 2002.

Gornitz, Vivien & Couch, Stephen (2001) "Chapter 3: Sea Level Rise and Coasts." In Climate Change and a Global City, ed. Cynthia Rosenzweig and William D. Solecki, 19-46. New York: Columbia Earth Institute.

Miller, Ron. Personal communication with Ron Miller. July 23, 2002.

The National Oceanic and Atmospheric Administration (NOAA)

Rosenzweig, Cynthia, and Solecki, William, "Climate Change and a Global City: Learning from New York". Environment, Vol. 43 Iss. 3, April 2001a.

Russell, G.L., Gornitz, V., Miller J.R. (2000). "Regional sea level changes projected by the NASA/GISS Atmosphere-Ocean Model." Climate Dynamics, 16:789-797.

Titus, James G. et. al, Greenhouse Effect and Sea Level Rise: The Cost of Holding Back the Sea.

The Weather Channel

Weather World


10. Coch, Nicholas K. "Hurricane Hazards Along the Northeastern Atlantic Coast of the United States". Journal of Coastal Research, Issue 12, pp. 115-147. (1993).
11. McCabe, Gregory, Clark, Martyn P. and Serreze, Mark C. "Trends in Northern Hemisphere Surface Cyclone Frequency and Intensity". Journal of Climate, June 15, 2001 pps. 2763 2768.