Other U.S. Cities Prone to Natural Disasters

By: Mark Bloomer, Meteorologist

 

The crisis that hit New Orleans at the end of August was an event emergency planners had been concerned about for many years. Much of the city is below sea level and when hurricane Katrina hit, the storm surge combined with rough seas caused breaks in the levee that flooded the city. The storm was well forecasted; however the magnitude of the disaster was greater than anything emergency responders had dealt with in the past. It left emergency planners asking how a response system could be organized to function much more efficiently in the event of another great disaster.

 

One of the questions forecasters and emergency planners may be asking is “what kinds of disasters are other cities vulnerable to?” New Orleans is not the only city vulnerable to large scale natural disasters. Many other American cities are prone to a major natural crisis including the three great cities of New York, Chicago and Los Angeles. It may seem gloomy to think of the potential for great disasters, but maintaining an awareness of what the forces of nature can do will keep both emergency planners and the civilian population aware and prepared. I am going to take a look at some specific American cities and cite some foreboding concerns that each may need to consider.

 

New York City is dangerously at risk for a serious coastal flood in the Long Island Sound. The occurrence of an extreme tide requires special conditions combining a very strong Nor’easter with an astronomical high tide. Very strong Nor’easters, the kind which produce wind fields around 70 knots in the open water, occur a couple times a year in the northeast. The Nor’easters that produce the highest storm surges in Long Island Sound take a track close to eastern Long Island producing a northeast wind. The force of the wind upon the water combined with an aquatic Coriolis force known as Eckman transport acts to push the waters at right angles to the wind field. This carries the water in toward the land resulting in a tide much above normal. Super astronomical tides most commonly occur either during spring nights at the time of the full moon or during fall days at the time of the new moon. The combination of a very strong Nor’easter taking the right track and an extreme spring tide are very rare, but could be catastrophic when they occur. The New York City subway system, and many coastal homes, could be submerged during an event of this kind. Being aware that an event like this is possible can help forecasters and emergency responders prepare well ahead of time. Plans to evacuate the New York City subway system and coastal New York and Connecticut should probably be put in place incase an extreme tidal flood ever occurs.

 

Chicago is at risk for a great blizzard which could strand hundreds of thousands of motorists if it hit with the right intensity and at the right time. One of the scenarios for very heavy snow in Chicago would be a low center slowly tracking northeast into western Ohio. A storm in this position may result in a north northwesterly wind over southern Wisconsin and northern Illinois and a north northeasterly wind over Lake Michigan resulting in strong coastal surface convergence near Chicago. Sharp surface convergence combined with vigorous upper level dynamics could combine to generate very heavy snowfall of 2 to 3 inches an hour for several hours in metro Chicago. Snowfall of this intensity can accumulate on road surfaces faster than snow removal crews can clear the roads. This would cause traffic to come to a stand still stranding commuters for hours or even days and putting them at risk for hypothermia or carbon monoxide poisoning. Awareness of this scenario can put emergencies planners including forecasters and local officials in a position of readiness to close roads ahead of time should this ever occur.

 

Boulder Colorado is at risk for a serious flash flood similar to the kind that hit Rapid City in 1972, Big Thompson in 1976 or Fort Collins in 1997. A large thunderstorm complex stationed over Boulder Canyon for several hours, producing close to a foot of rain, could send a surge down the narrow Canyon taking out much of downtown Boulder.

 

Other potential natural disasters include earthquakes and tsunamis along the west coast, fires in California and the Rockies and great tornadoes in the plains.

 

For many of these disasters, it’s not a matter of if they will occur, but when they will occur. Being aware of the risks can prepare cities ahead of time for their potential. New York City needs a very close and cooperative line of communication between the National Weather Service and the New York City transit authority. The transit authority has to have a plan for stopping the trains and getting people out to the streets above in hour’s notice of a flood. The City of Chicago and the cities of the northeast have to strategize a means for getting people off the roads before a blizzard. Boulder needs a flash flood warning system and an evacuation plan in the event of a flood.

 

Preparation for a natural disaster must occur at many levels. Being aware of the risks that each city or location has is the first step. Having the forecasters and observing equipment in place to forecast and issue warnings is another important element. Aggressive communication of the warnings is essential for making sure that everyone who needs to be warned receives the warnings and is aware of how they need to respond. The infrastructure of the town or city should be designed to allow people to evacuate and responders to enter in a rapid and efficient way. There are many areas vulnerable to a variety of natural disasters. But being aware is the first step to being prepared.

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