Floods
Floods are when water overflows from the normal boundaries of a stream, river or other body of water, or accumulates in an area that is usually dry.There are two main types of floods. Inundation floods are slow and develop over hours or days. Flash floods occur suddenly, often without warning and usually due to heavy rain. Though annual flooding is a natural phenomenon in many parts of the world, human habitation and land-use practices have led to an increase in frequency and size of floods. Floodsare also predicted to become even more frequent and severe in future due to climate change. Floods can be extremely dangerous and cause massive human, environmentaland material damage to communities.
Cyclones
Tropical cyclones are rapidly-rotating storm systems that rotate (counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere) around a low pressure centre. They are generally slow moving but severe, with winds of between 120-320 kilometres an hour. They have different names depending on where they happen:cyclonesin Southeast Asian waters and the Indian Ocean, typhoonsin East Asian and Pacific waters and hurricanesin the Atlantic, Gulf of Mexico or Caribbean sea. Most cyclone-related deaths are from flooding, but also from electrocution, collapsed structures and blowing debris.
Technological and biological hazards
Technological hazards originate from technological or industrial conditions, dangerous procedures, infrastructure failure or human activity. Chemical, biological, radiological and nuclear (CBRN) hazards are all types of technological hazards. They are commonly grouped together because they share lots of similarities, and many of the preparedness and response measuresare the same or very similar. Learn more about these specific hazard types below.
Volcanic eruptions
A volcano is an opening in the earth’s surface that allowsmagma (hot liquid and semi-liquid rock), volcanic ash and gases to escape. They are generally found where tectonic plates come together or separate, but they can also occur in the middle of plates due to volcanic hotspots. A volcanic eruption is when gas and/or lava are released from a volcano—sometimes explosively. Volcanoes provide a number of environmental benefits, for example: fertile soils, hydrothermal energy, and precious minerals. But they also pose several hazards: volcanic ash, gases, lahars (mud flows), landslides, lava flows, and pyroclastic flows (fast-moving currents of hot gas). Volcanic eruptions can be deadly and often cause population displacement and food shortages.
Tsunamis
A tsunami is a sea wavetriggered bya large-scale displacement of the sea floor. They are most commonly caused by earthquakes but can also be causedby major underwater (or 'submarine') landslides or volcanic eruptions. They can strike any coast at any time.Tsunamis can move as fast as a jet plane across the open ocean and can hit land with waves higher than 20 metres. Water canwash inland for several kilometres in flat lying areasand move up streams and rivers, destroying everything in its path. Waves may continue to strike the shoreline for many hoursand dangerous currents can continue for several days.Although a tsunami can't be prevented, its impact can be reduced when communities understand the risks, receive timely warnings and know how to respond.
Landslides
A landslide or landslip is the mass movement of rock, debris, earth or mud down a slope.While most landslides are caused by gravity, they can also be caused by rainfall, earthquakes, volcanic eruptions, groundwater pressure, erosion, destabilization of slopes as a result of deforestation, cultivation and construction, and snow or glacial melt. Debris flows, or mudflows, are fast-moving landslides that are especially dangerous due to their speed and volume. Some debris flows havebeen recorded as reaching speeds of over 160 kilometres per hour.
Epidemics and pandemics
Epidemicsare an unexpected, often sudden, increase of a specific illness within a community or region.Pandemicsare when an epidemic occurs worldwide, crossing international borders and affecting a large number of people.A number of communicable diseasescan be significant health threats at the local, regional andglobal leveland leadto epidemics or pandemics. Epidemics and pandemics can be prevented and mitigated through a range of household and community measures, such as good hygiene, social distancing and vaccination.
Droughts
Drought is a long-lasting period of low precipitation (rainfall, snowfall or snowmelt)resulting in a shortage of water. When communities don't have enough water for drinking, sanitation and agriculture it can lead tofood insecurity, the spread of disease, malnutrition and starvation, migration and economic losses. Drought can also have a negative impact onpower generation, transportation and commercial or industrial needs in a country.
Hailstorms
Hail is a type of solid rain made up of balls or lumps of ice. Storms that produce hail which reaches the ground are known as hailstorms. They typically last for no more than 15 minutes but can cause injuries to people and damage buildings, vehicles and crops. When hail builds up it can cause a loss of power, bring down trees and cause flash floods and mudslides in steep areas. Hailstorms can sometimes be accompanied by other severe weather events, such as cyclones and tornadoes.On rare occasions, massive hailstones have been known to cause concussions andfatal head injuries.
Wildfires
Wildfires (also known as bushfires, brush fires or forest fires) arelarge, uncontrolled and potentially destructive fires that can affect both rural and urban areas.They can spread quickly, change direction and even 'jump' across large distances when embers and sparks are carried by the wind. They are caused by a range of natural causes (such as lightning) or by human carelessness (such as a discarded cigarette). The spread of a wildfire depends onthe arrangement of land,available fuel (vegetation or dead wood)and weather conditions (wind and heat). They can start in just seconds and turn into infernos in a matter of minutes.
Avalanches
An avalanche, sometimes called a snowslide,is the rapid flow ofsnow, ice and/or rockdown a slopeor mountain.Theycan be triggered by natural forces such as precipitation, earthquakesor the weakening of snowpack (layers of slow that accumulate in areas of high elevation and cold temperatures). They can also be caused by human activity when someone walks or rides over a weak area of snow. Slab avalanches—when a large slabof stronger ice or snow dislodges from ontop of a weaker snow layer—are the most dangerous. Avalanches can obstruct everything in their path, destroy entire buildings and lead to serious injury and death.
Earthquakes
An earthquake is a sudden andrapid shaking of the ground caused by the shifting of rocks beneath the earth’s surface, or by volcanic or magmatic activity in the earth. Earthquakes strike suddenly, without warning, and can occur at any time. Theycan lead to death, injuries, property damage, loss of shelter and livelihoodsand disruption of critical infrastructure.Most deaths are due to buildingscollapsing or to secondary hazards, such as fires, tsunamis, flooding, landslides and release of chemicals or toxic materials.
Cold waves
A cold wave, sometimes knownas a cold snap or deep freeze, is a weather event involving a cooling of the air,or the invasion of very cold air, over a large area. It is marked by a drop of average temperature well belowthe averages of a region. Cold waves can havenegative impactson people, crops, properties and services. Theycan be preceded or accompanied by significant winter weather events, such as blizzards or ice storms. And they can feel even colder during periods of high winds.
Heat waves
A heat wave is an extended period of unusually high temperatures and often high humidity.They are expected to become more frequent and more severe in future due to climate change. People affected by heat waves cansufferfrom shock, becomedehydrated and developserious heat illnesses. Heat waves can also worsenchronic cardiovascular and respiratory diseases.