From: Roger Greenway, ENN
Published October 28, 2012 07:52 AM

Hurricane or Tropical Storm, Sandy packs a punch

As Hurricane Sandy approaches the Mid-Atlantic coast of the US, it is creating major concerns for prolonged heavy rain and a significant storm surge with the potential for serious flooding and beach erosion. The unfortunate coincidence of a full moon on Monday exacerbates high tides and will only add to the potential for coastal flooding. 

The ability to predict flooding from storms like Sandy will be improved by work being undertaken by the US Geological Survey.

The USGS is installing more than 150 storm-tide sensors at key locations along the Atlantic Coast -- from the Chesapeake Bay to Massachusetts -- in advance of the arrival of Hurricane/Tropical Storm Sandy.

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Working with various partner agencies such as NOAA, FEMA, and the U.S. Army Corps of Engineers, the USGS is securing the storm-tide sensors, frequently called storm-surge sensors, to piers and poles in areas where the storm is expected to make landfall. The instruments being installed will record the precise time the storm-tide arrived, how ocean and inland water levels changed during the storm, the depth of the storm-tide throughout the event, and how long it took for the water to recede.

"In the hours and days before Irene made its epic sweep up the eastern seaboard last year, USGS deployed a record number of storm-surge sensors that yielded important new information on storm tides along some of the most populated coastline in the United States," said USGS Director Marcia McNutt. "Now with Sandy we have the opportunity to test and improve predictive models of coastal zone impact based on what we previously learned."

Storm-tides are increases in ocean water levels generated at sea by extreme storms and can have devastating coastal impacts. In locations where tidal forecasts are known, the sensors being installed can also help determine storm surge. For differences between storm-surge and tidal-surge, visit the National Hurricane Center's website.

This information will be used to assess storm damage, discern between wind and flood damage, and improve computer models used to forecast future coastal inundation.

In addition, rapid deployment gauges will be installed at critical locations to provide real-time information to forecast floods and coordinate flood-response activities in the affected areas. The sensors augment a network of existing U.S. Geological Survey streamgages, which are part of the permanent network of more than 7,500 streamgages nationwide.

Of the sensors deployed specifically for Sandy, eight have real-time capability that will allow viewing of the storm-tide as the storm approaches and makes landfall. Besides water level, some of these real-time gauges include precipitation and wind sensors that will transmit all data hourly. All data collected by these sensors and the existing USGS streamgage network will be available on the USGS Storm-Tide Mapper link at www.usgs.gov/hurricanes.

Graphic shows the difference that storm surge makes to a normal high tide. Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases. (USGS)

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