This article was provided by AccuWeather.com.
The fourth week of June 2012 is the 40th anniversary of one of the first billion-dollar hurricanes in the history of the United States.
While many people across the Midwest, South and West may not remember the fateful week of June 1972, most residents at least a few years of age at the time in the Northeast will never forget the weather that week and the name "Agnes."
A mass of clouds over the Yucatan grew more organized on June 14, 1972. What would soon become a hurricane of minimal strength in terms of wind and storm surge would soon lead to, according to President Nixon, "The greatest natural disaster in the history of the United States."
Nixon made the statement after viewing the damage in Agnes' wake firsthand. Agnes occurred only a few years after billion-dollar hurricanes Betsy in 1965 and Camille in 1969. Damage from Agnes would not be exceeded by a hurricane in the U.S. until 20 years later during Andrew in 1992.
After making landfall on the Florida Panhandle on June 19 as a minimal hurricane, Agnes weakened to a tropical depression over the southeastern U.S. However, the storm was able to survive and strengthen to a tropical storm once again by moving off the mid-Atlantic coast. National Oceanic and Atmospheric Administration (NOAA) image taken on June 19, 1972, as Hurricane Agnes reached the Florida Panhandle from the Gulf of Mexico.
A non-tropical weather system soon captured Agnes and caused the storm to loop northwestward over Pennsylvania, New Jersey and New York. The topography, tropical moisture and energy resulted in up to 19 inches of rain and massive flooding spanning June 20 to 26, following an already wet spring for the region.
The Susquehanna River, which feeds into the Chesapeake Bay, bore the brunt of Agnes' rainfall. The amount of fresh water flowing into the bay during a several-day period, on the order of trillions of gallons, negatively affected local marine life and the seafood industry for several years.
Record flooding swept much of the Susquehanna Watershed from New York state to northern Maryland.
The worst flooding and damage occurred in the Wyoming Valley of Pennsylvania and the Elmira, N.Y., area.
In Wilkes-Barre, within Wyoming Valley, the Susquehanna crested at a then record of 40.9 feet.
All told, Agnes claimed the lives of 122 people.
According to the National Weather Service, total damage from Agnes was over $3.0 billion in the U.S. Adjusted to today's dollars, this would be well over $16 billion. Agnes also caused extensive damage to railroad lines in the region, already taxed by bankruptcy.
While the Agnes disaster has been eclipsed by more powerful and costlier storms during recent decades, including hurricanes Andrew and Katrina, it still ranks in the top 10 costliest hurricanes in the U.S., adjusted to today's dollars.
The name Agnes has been retired from the list of Atlantic hurricanes, by the World Meteorological Organization. The storm forever changed people's lives and the landscape from New York state to Virginia.
Agnes, a minimal hurricane, was only one of four named tropical storms of the 1972 Atlantic Hurricane Season. It goes to show that you do not need a powerful hurricane or a large number of lesser hurricanes making landfall in a single season to cause great loss of life and tremendous property damage.
Jim Ludlam, U.S. Army Corps of Engineers civil engineer, surveys the swollen Susquehanna River here, Sept. 8, 2011. The Baltimore District sent a team of eight engineers to provide technical assistance to Luzerne County during the record flooding. The Market Street Bridge is seen in the background. (U.S. Army Corps of Engineers flickr photo by Ashley A. Williams)
The one-two punch from Irene and Lee from the 2011 season proved this point.
Back in 1972, it was much more difficult to judge runoff from the relatively sparse network of rainfall and river gauges, compared to today.
In 2012, a much greater number of rain and stream gauges, along with radar rainfall estimates and computer analysis are incorporated into the National Weather Service's sophisticated flood warning system.
However, the system is not foolproof.
During the event of September 2011, a river level gauge in Wilkes-Barre, Pa., which can be monitored online, stopped working when the reporting equipment was overtaken by rising waters.
The gauge continuously recorded a water level and false crest of 38.5 feet, when in fact the river rose several feet higher, seeped through bridge flood gates and almost topped levees at 42.7 feet.
The current levees were designed to protect the area for river level up to 41 feet. In Wyoming Valley, the levee system towers 30 feet above the landscape in some areas.
Just as the location of the recording equipment is essential for accurate forecasts, maintenance and upgrading of levee systems are essential for flood prevention. Fortunately for most residents of Wyoming Valley, the levees and pumping stations were recently upgraded.
Several communities not protected by levees sustained major flooding in the wake of Lee during September 2011 including Bloomsburg, Shickshinny, Plymouth and West Pittston.
Significant flooding was avoided in much of the heavily-populated Wilkes-Barre, Kingston and Harrisburg areas with Mother Nature's latest stint, but just barely so.
Water levels exceeded the design of the levees in September 2011, but the system held with water coming within inches of the top.
This past September was a reminder that a 100- or 200-year rainfall event can occur more often than the parameter suggests. Precipitation frequency is available by NOAA's Atlas 14.
Rainfall matching that of 1972 can occur every couple of years or not occur again for hundreds of years. Case in point Tropical Storm Lee in 2011. They are but averages used by the insurance and construction industries.
Since the September 2011 flooding incident, a new pressure-sensing river gauge at Wilkes-Barre has been installed on the Pierce Street Bridge, and officials from the United State Geological Survey stated it will work properly to a river level of around 48 feet. This is several feet above the current top of the levee system upgrade completed in 2003.
Flooding is a way of life along river systems, and the valleys of the Susquehanna are no exception.
According to an article published in the Wyoming Valley Observer in July of 1972 and reprinted in the book "The Great Flood of 1972," flooding in the Wyoming Valley has been documented as far back as the late 1700s with talk of routine flooding long before by Native Americans.
Levees spared much of Wyoming Valley during Hurricane Eloise in September 1975 and the "Meltdown of January 1996."
The odds of another rain event like 1972 or 2011 occurring in our lifetime are slim. However, as more forests are bulldozed and grassy areas are paved over, the control of runoff will become increasingly important for preventing or minimizing flooding.