Coastal resilienceLocation matters: Sandy’s tides hit some parts of the N.J. coast harder than others

Published 21 November 2016

USGS researchers ground-truthed Hurricane Sandy’s October 2012 storm tides in New Jersey and found northern coastal communities had significantly higher storm tides than southern ones did, though flood damage was widespread in both areas. The findings suggest that some southern New Jersey communities may be underestimating their future flood risks.

USGS researchers ground-truthed Hurricane Sandy’s October 2012 storm tides in New Jersey and found northern coastal communities had significantly higher storm tides than southern ones did, though flood damage was widespread in both areas. The findings suggest that some southern New Jersey communities may be underestimating their future flood risks.

USGS says that while Hurricane Sandy produced record flooding and damage in most areas along the coast of New Jersey, storm tide levels in many northern New Jersey locations were not only higher than in Southern New Jersey, they were significantly higher than the federal flood insurance program’s latest “base flood” — the flood that has a one-in-100 chance of happening in any given year.

That is a key finding of a new U.S. Geological Survey study, published soon after the fourth anniversary of Hurricane Sandy’s landfall in New Jersey 29-30 October 2012, that reveals local variations in the storm’s flood tides. The researchers found that peak storm tide elevations along the northern coast of New Jersey and Raritan Bay generally ranged from about 9 to 15 feet. Along the central and southern coast from Ocean to Cape May counties the peak water levels generally ranged from about 5 to 8 feet.

USGS researchers and Federal Emergency Management Agency officials often describe storms’ highest flood tides in terms of their odds of occurring at a specific place in any given year. A flood that has a one-in-100 chance of occurring in any given year may be described as a “one percent flood” or a “base flood,” and a flood that has a one-in-500 chance of occurring any year as a “0.2 percent flood.”

How extreme was the flooding caused by Hurricane Sandy? In some northern areas, the highest storm tides were two feet or more higher than that one-in-100 flood risk, the one percent flood, and six inches or more higher than the one-in-500 flood risk, or the 0.2 percent flood.

In southern New Jersey, the pattern is different, the new USGS research shows. In some parts of southern New Jersey peak storm tide levels did not reach the one-in-100-chance flood level, although many communities in these areas experienced severe damage from the storm.