Storm surges a major threat during hurricane

By far the biggest danger presented by Hurricane Sandy: its storm surge. Latest estimates say it could reach a height of 6-11 feet. To offer some perspective, New York City’s seawall is about 5-feet-high.

The topic is particularly pertinent, since Sandy may strike at a time when storm surges will be at their strongest.

Storm surges account for most of the death and damage caused by hurricanes — according to the NOAA, almost all the devastation from 2005’s Hurricane Katrina was caused by surges — but the phenomena isn’t commonly understood.

Storm surges accounted for most of the flooding in the disastrous Hurricane Katrina that heavily damaged New Orleans in 2005.

The flooding that happens during a storm is not just because of heavy rains; the intense pressure of a hurricane, coupled with the forceful wind actually pushes a huge volume of water onto the shore and that rush of water comprises a storm surge.

The NOAA has a graph showing the science behind the surge:

Storm surging during Katrina was around 25 ft above normal tides. According to another NOAA report, in New England, the time of day the storm hits will make the biggest impact on the size of the flood. Low tide will reduce the impact, but high tide will exacerbate the water levels. Unfortunately, if Sandy keeps on its current path, the tide will be high for many parts of Southwestern Connecticut when it hits.

The size of a continental shelf also impacts surge size: shallow shelves tend to create worse surges.

The size of the surge is extremely important; one of the worst hurricanes to hit Connecticut though, in 1938, storm surges raised the coastal water levels by 40 feet, according to the Boston Globe.

You can check out pictures of that storm below, and be sure to take a look at our feature on Connecticut’s worst hurricanes.

Chris Duray