Hazards

A dam failure is the collapse or breach of a dam that causes downstream flooding. Dam failures may be caused by natural events, manmade events, or a combination. Due to the lack of advance warning, failures resulting from natural events, such as earthquakes or landslides, may be particularly severe. Prolonged rainfall and subsequent flooding is the most common cause of dam failure.

Drought is a deficiency in precipitation over an extended period. It is a normal, recurrent feature of climate that occurs in virtually all climate zones. However, drought can affect people’s health and safety. It has the potential to impact water supply, agricultural yields, and water-dependent industries. Drought conditions can also increase the likelihood of wind erosion and increase wildfire risk.

An earthquake is a movement or shaking of the ground. Most earthquakes are caused by the release of stresses accumulated as a result of the rupture of rocks along opposing fault planes in the Earth’s outer crust.

Flooding is defined by the rising and overflowing of water onto normally dry land. Flooding can result from an overflow of inland waters or an unusual accumulation or runoff of surface waters from any source.

A hazardous material is any item or agent (biological, chemical, physical) which has the potential to cause harm to humans, animals, or the environment, either by itself or through interaction with other factors. A release or spill of bulk hazardous materials could result in fire, explosion, toxic cloud or direct contamination of people and property. The effects may involve a local site or many square miles. Health problems may be immediate, such as corrosive effects on skin and lungs, or be gradual, such as the development of cancer from a carcinogen. Damage to property could range from immediate destruction by explosion to permanent contamination by a persistent hazardous material.

Tropical cyclones are storm systems that are characterized by low pressure, high winds, numerous thunderstorms and heavy rain. These storms are hazards that can produce widespread destruction that has the potential for lasting effects. The primary damaging forces associated with these storms are high-level sustained winds, heavy precipitation, and tornadoes.

Infectious disease is a public health threat that can cause isolation, quarantine, and potential mass casualties. Disease spread and mortality is affected by a variety of factors, including virulence, ease of spread, aggressiveness of the virus and its symptoms, resistance to known antibiotics and environmental factors. Impacts of infectious disease can range from school and business closings to the interruption of basic services.

A nuclear or radiological incident is an occurrence resulting in the release of radiological material. Often, this type of incident results from damage to the reactor of a nuclear power plant. The release could affect the natural environment as well as the health and safety of anyone in its path.

Severe cold weather storms can involve heavy snowfall and/or ice accumulation (generally noted when accumulation reaches ¼ inch or more), often accompanied by extreme cold, which can result in blocked roads, dangerous road and sidewalk conditions, downed trees and power lines, and hypothermia.

Thunderstorms result from the rapid upward movement of warm, moist air. They can occur inside warm, moist air masses and at fronts. Severe thunderstorm winds arise from convection and have speeds of at least 58 mph, or are winds of any speed producing a fatality, injury or damage. Lightning is an electrical discharge between positive and negative regions of a thunderstorm. Each year, lightning is responsible for deaths, injuries, and millions of dollars in property damage across the country, including damage to buildings, communications systems, power lines, and electrical systems. Lightning also causes forest and brush fires. Hail is associated with thunderstorms that can also bring high winds and tornadoes. It forms when updrafts carry raindrops into extremely cold areas of the atmosphere where they freeze into ice. Hailstones are usually less than two inches in diameter and can fall at speeds of 120 mph.

Temperature extremes encompasses extreme heat and extreme cold, both of which can pose a risk to the life and wellbeing of individuals. Extreme heat events are one of the leading weather-related causes of death in the United States. Extreme high temperatures compromise the body’s ability to regulate its temperature, which can result in a cascade of illnesses and can aggravate chronic conditions. Extreme cold can cause frostbite and hypothermia. Both extreme heat and extreme cold can have enormous economic costs in terms of agriculture, energy, infrastructure, production, and transportation.

Terrorism is defined in the United States by the Code of Federal Regulations as: “the unlawful use of force and violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objectives.” A terror threat is generally more likely to be targeted at a critical or symbolic location. An active shooter is an individual actively engaged in killing or attempting to kill people in a populated area, and recent active shooter incidents have underscored the need for a coordinated response by law enforcement and others to save lives.

A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Microbursts are minimized downbursts covering an area of less than 2.5 miles across. They include a strong wind shear (a rapid change in the direction of wind over a short distance) near the surface. Microbursts may or may not include precipitation and can produce winds at speeds of more than 150 miles per hour.

Urban fire occurs primarily in cities or towns with the potential to rapidly spread to adjoining structures. These fires damage and destroy homes, schools, commercial buildings, and vehicles. Urban fire risk can be heightened during periods of rapid urban development.

A wildfire is an uncontained fire that spreads through the environment. Wildfires have the ability to consume large areas, including infrastructure, property, and resources.

Winter weather can range from a moderate snow over a period of a few hours to blizzard conditions with blinding wind-driven snow. Events may include snow, sleet, freezing rain, or a mix of these wintry forms of precipitation and can be accompanied by extreme cold temperatures. Some winter storms might be large enough to affect several states, while others might affect only localized areas. Winter storms and ice can result in blocked roads, dangerous road and sidewalk conditions, roof collapses and property damages, downed trees and power lines, and hypothermia.