How Aging Dams Are Storing Up Trouble
Dams are a vital part of our national infrastructure in the United States. Dams provide trillions of gallons of water for drinking, as well as for irrigation and industrial use; they also play a vital role in flood control, supplying hydroelectric power, recreation facilities and navigation.
But the potential danger to the population posed by dams, and the risk they represent to the insurance industry, is enormous as well. Dam breaks witnessed during the recent flooding in South Carolina, or in Colorado in 2013, exposed the fragility of vital infrastructure that protects millions of people and billions of dollars of property.
To get a better understanding of the potential exposure involved, it’s worth reflecting on some startling facts and figures provided by the American Society of Civil Enginees (ASCE). There are 84,000 dams in the U.S., according to the ASCE 2013 Report Card for America's Infrastructure.
The average age of these dams is 52 years and proper maintenance is critical in preventing the possibility of a dam failure. Fifty years ago dams were built to the best engineering and construction standards of the time. However, as scientific and engineering data have improved, many dams are not expected to safely withstand current predictions regarding large floods and earthquakes.
Dams are classified based on their hazard potential - the anticipated consequences in the case of failure. As of 2012, 13,991 dams were rated as high hazard: By definition, the failure of such a high hazard dam is anticipated to cause a loss of life. Many of these high hazard dams were originally built as low-hazard dams, protecting undeveloped agricultural land and thus were not constructed to the more stringent design criteria for high hazard dams.
Another 12,662 dams are currently labeled as significant hazards, meaning a failure would not necessarily cause loss of life, but could result in significant economic losses.
With the tremendous amount of development that’s taken place in the past 50 years, many of these dams now protect schools, expensive homes, office parks and industrial areas. As the U.S. population grows, the number of high hazard dams will also increase (numbers went up from 10,118 to 13,991 in the years 2002 - 2012).
Worryingly, of the nearly 14,000 high hazard dams in the U.S., about 2,000 are considered deficient (i.e., those with structural or hydraulic deficiencies, leaving them susceptible to failure).
As we see it, the big issue is that inundation mapping of a dam breach is very different from what is seen on the 100-year flood maps published by FEMA for the same area. FEMA flood maps identify flood zones as areas where storm flooding is possible from a "100 year event.” Dam failure inundation, in contrast, is flooding that could result from the failure of a dam upstream, following an earthquake or other catastrophic event.
In other words, you may be exposed to significant risks of which you are not even aware. Our experts are working with our clients on risk mapping that specifically takes account of high hazard dams now - before it’s too late.