News•October 27, 2012

Hurricane Sandy's Five-Fold Flood Threat, with Local Maps

Land vulnerable to coastal flooding in Norfolk, Va., lying less than 4 feet above high tide.Click image to enlarge. Credit: Surging Seas/Climate Central

Hurricane Sandy threatens to cause major coastal flooding from North Carolina to Maine. Use the links below to see interactive maps of low-lying areas in vulnerable cities throughout the Eastern seaboard, or jump to our main map, type in your zip code or city name, and choose the water level to view. From North Carolina through Maine, nearly 900,000 people live on land less than 4 feet above the local high tide line, according to Climate Central research. Approximately 650,000 live on land below 3 feet, and 1.2 million below 5 feet.

Immediate Risk Factors and Sea Level Rise

Coastal flood risks are high for at least five reasons:

COASTAL FLOODING
A list of low-lying cities vulnerable to major coastal flooding from Hurricane Sandy.

Bridgeport, CT
Norwalk, CT
Stamford, CT
Washington, D.C.
Boston, MA
Cambridge, MA
New Bedford, MA
Baltimore, MD
Ocean City, MD
Wilmington, NC
Atlantic City, NJ
Hoboken, NJ
Jersey City, NJ
Freeport, NY
Long Beach, NY
New York, NY
Oceanside, NY
Providence, RI
Chesapeake, VA
Hampton, VA
Norfolk, VA
Virginia Beach, VA

Sandy is projected to create tall storm surges, due to an enormous wind field influencing wide areas of ocean, and the direct angle of the storm's projected approach toward land.
The surge may be prolonged, due to the storm’s large size and slow movement. This means many areas will experience surge combined with at least one high tide.
With a full moon near, tides are running high to begin with.
Rivers swollen by significant rainfall may compound tides and surge locally.
Sea level rise over the past century has raised the launch pad for storms and tides to begin with, by more than a foot across most of the Mid-Atlantic. Sinking land has driven part of this rise, but global warming, which melts glaciers and ice sheets and expands ocean water by heating it, appears to be the dominant factor across much of the region.

Maps

Our maps (see list to the right, our main map, or this embeddable widget) show low-lying areas to suggest an overall picture of potential vulnerability, but they do not predict where flooding will actually occur and should absolutely not be used for emergency planning. We do not take seawalls, levees or other potential barriers into account, and we do not predict the actual movement of water. As the storm gets closer to land, the National Weather Service may be issuing official storm surge projection maps maps and we will link to them if and when available.

We show low-lying areas relative to the local high-tide line, or, technically, local Mean High Water (MWH). Our links show areas less than 4 feet above MHW; however, once on our maps, you may adjust them to look at any water level.

Continuously Updated Local Flood Level Projections

Here are sites providing updated local flood level projections based on physical models:

For North Carolina through New Jersey: National Weather Service. As of Saturday morning, some degree of flooding higher than the highest tide of the year is projected at nearly every station (those colored red). Click on any water level station (square) for 72+ hour projections. On the chart then shown, subtract the value next to “MHHW” on the left, from the highest value anywhere on the black line (the highest flood projection), to get a value to use as the water level in Climate Central’s tool.
For Delaware through Maine: National Weather Service page. As of Saturday morning, some degree of flooding higher than the highest tide of the year is projected at nearly every station south of Providence, R.I. Use the same instructions as above.
Alternate projections for Ocean City, Maryland through Newport, Rhode Island based on a localized model: Stevens Institute of Technology Urban Ocean Observatory. Click on the link to any station, and then select “MHW” as your “Datum” in the left-hand panel to get water level values in the upper right hand graph that you can then plot in Climate Central’s tool.