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New Hampshire can experience any natural disaster that can occur anywhere in the world, with the sole exception of a volcanic eruption. The state has no active volcanoes. Natural disasters have historically not occurred as frequently in New Hampshire as in other parts of the world, but they could potentially be as large and as devastating. The following is a brief overview of these hazards.
Earthquakes
New Hampshire is considered to be an area of moderate seismic hazard. This means that the state could experience large (6.5-7.0 magnitude) earthquakes, but they are not likely to occur as frequently as in a high hazard area like California. The state typically experiences one or two earthquakes per year registering magnitude 2.0 to 3.5.
According to the New Hampshire Bureau of Emergency Management and the US Geological Survey, the overall earthquake risk to the state is high. This is because of the built environment of New Hampshire. That is, many structures in the state (e.g., buildings, homes, bridges, and highways) are old or not built to modern earthquake standards. Hence, they are unable to withstand quakes. Additionally, due to the unique geology of New Hampshire, earthquake propagation waves travel up to 40 times further than they do in the western United States. This means the area of damage could be larger.
Recognizing the significant danger posed by seismic activity in the New England region, the US Geological Survey is presently installing the Advanced National Seismic System in Boston and New York City to provide emergency responders with real-time earthquake information.
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Hurricanes
All coastal states from Texas to Maine are at risk from hurricanes and New Hampshire is no exception. The primary threats associated with hurricanes come from coastal storm surge, inland flooding and severe winds. The largest recorded hurricane to strike New Hampshire was the ‘Great New England Hurricane of 1938’ which caused $22 million (in 1938 dollars) in direct damage and killed 13 people. A repeat of this event today would be devastating. The state’s population has more than doubled since 1938 and New Hampshire lacks a statewide building code to enforce wind-resistant construction standards.
Hurricane Bob dealt New Hampshire a glancing blow in 1991 yet still was responsible for $2.5 million in damage and 3 deaths. It is important to note that tropical storms below hurricane intensity have been responsible for some of the worst inland flooding experienced in the Northeast. Moving slowly and carrying lots of moisture, tropical storms can produce rain of several inches per hour. The New Hampshire Bureau of Emergency Management has worked with the US Army Corps of Engineers in producing and distributing storm surge evacuation maps to all coastal communities to aid them in decision-making as a hurricane approaches our coast.
Approximately 10 hurricanes have struck New Hampshire in recent years, the last being Hurricane Floyd in 1999.
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Floods
The most common hazard in New Hampshire is flooding. Every year some part of the state experiences either coastal or inland flooding. The two largest floods occurred in 1936 and 1938 costing the state millions in dollars and several lives. Though normally occurring in the spring from a combination of snow melt and rain, as was the case in 1936, floods may strike the state at any time of the year.
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Severe Winter Storms
Though snowstorms are taken in stride in New Hampshire and are a source of income to the state though the ski and snowmobile industries, they can cause severe damage and death. Heavy wet snow has caused wide spread power outages and the collapse of many buildings. If these storms produce freezing rain and ice the recovery may take weeks as in the ice storm of January 1998. More than 79,000 people were without power as a result of that storm, some for nearly a week.
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Ice Storms
When a mass of warm moist air collides with a mass of cold arctic air, the less dense warm air will rise and the moisture may precipitate out in the form of rain. When this rain falls through the colder more dense air and comes in contact with cold surfaces, the latent heat of fusion is removed by convective and/or evaporative cooling. Ice forms on these cold surfaces and may continue to form until the ice is quite deep, as much as several inches. The buildup of radial ice may strain branches of trees, power lines and even transmission towers to the breaking point and often creates treacherous conditions for highway travel and aviation.
Notwithstanding the unique beauty of such events, the weight of radial ice may cause power and phone lines to snap and the towers that support them to fail under the load of ice and bending or broken tree limbs. Debris in roads makes emergency access, repair and cleanup extremely difficult.
The Ice Storm of January 1998 was the most costly declared disaster in New Hampshire's history. The storm caused significant damage to the state’s forests. The woody debris from this event remains scattered through forests and continues to be a fire hazard. The Ice Storm of January 1998 was not unique; a similar event occurred in 1929.
The US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire, estimates a 40 – 90 year return period for an event with a uniform ice thickness of between .75 and 1.25 inches. Other events with similar accumulations and smaller affected areas have been recorded since 1929.
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Wildfires
Large wild land fires are typically associated with the western states, although they are possible in New Hampshire. Historically, New Hampshire’s large wildfires run in 50-year cycles. With some of the state’s largest wildfires occurring in the late 1940’s many people believe we are overdue for the next bad fire season.
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Tornadoes and Severe Winds
Roughly two tornadoes are reported in New Hampshire a year. Most of these are of an intensity of F1 or 2 and cause localized damage. But, as with most other natural hazards, we have and will experience large events. The largest reported tornado to strike the state occurred on September 1821. This tornado, estimated at F4, had a path half a mile wide, killed 6, injured hundreds and left thousands homeless.
The southwestern portion of the state is considered a special wind hazard area as demonstrated by the high proportion of tornadoes and severe wind events that are experienced there annually. On July 3, 1997 several tornadoes struck this section of the state. An F1 tornado caused severe tree loss in Swanzey, destroying a building and damaged the stables at the Cheshire Fairgrounds. At the same time a F2 tornado struck Greenfield causing damage to a summer camp, the recycling center and completely destroying a lumber facility. Fortunately, no deaths resulted from these events.
Downbursts
A downburst is a severe localized wind blasting down from a thunderstorm. These "straight line" winds are distinguishable from a tornado’s circular pattern of destruction and debris.
Depending on the size and location of these events, the destruction to property may be devastating. Downbursts have produced winds as strong as 175 mph. Winds of this intensity can cause severe damage to forests and structures are certainly life threatening.
Downbursts have severely affected several areas of New Hampshire. On August 18, 1991, five people were killed and 11 injured in Stratham. This downburst also caused almost $2.5 million in damage. In 1994, a downburst left a path one-half mile wide and 4-6 miles long in the town of Moultonborough while on July 6, 1999, two people were killed when a downburst struck central New Hampshire.
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Drought
In the past several years, La Nina and El Nino currents in the Pacific Ocean have influenced America’s weather pattern. Since1999, large tracts of the United States, including New Hampshire, have experienced drought conditions for several months at a time. Drought not only hinders agricultural productivity and endangers the public water supply, but it also significantly amplifies the risk of wildfire.
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Thunderstorms-Lightning
It is for good reasons that lightening is called the "Underrated Killer"! New Hampshire is ranks 16 th in the nation for casualties from lightning strikes. Nationally lightning kills and injures over 400 people a year, some sources believe this number to be twice as large. Please look at these related links… it could save your life or those of your loved ones!
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