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Heavy rainfall and flooding

A flash flood caused by a severe thunderstorm

{{#invoke:main|main}} Heavy rainfall can lead to a number of hazards, most of which are floods or hazards resulting from floods. Flooding is the inundation of areas that are not normally under water. It is typically divided into three classes: River flooding, which relates to rivers rising outside their normals banks; flash flooding, which is the process where a landscape, often in urban and arid environments, is subjected to rapid floods;<ref name="Glossary2009f">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and coastal flooding, which can be caused by strong winds from tropical or non-tropical cyclones.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Meteorologically, excessive rains occur within a plume of air with high amounts of moisture (also known as an atmospheric river) which is directed around an upper level cold-core low or a tropical cyclone.<ref name="Boniface2010"></ref> Flash flooding can frequently occur in slow-moving thunderstorms and are usually caused by the heavy liquid precipitation that accompanies it. Flash floods are most common in dense populated urban environments, where less plants and bodies of water are presented to absorb and contain the extra water. Flash flooding can be hazardous to small infrastructure, such as bridges, and weakly constructed buildings. Plants and crops in agricultural areas can be destroyed and devastated by the force of raging water. Automobiles parked within experiencing areas can also be displaced. Soil erosion can occur as well, exposing risks of landslide phenomena. Like all forms of flooding phenomenon, flash flooding can also spread and produce waterborne and insect-borne diseases cause by microorganisms. Flash flooding can be caused by extensive rainfall released by tropical cyclones of any strength or the sudden thawing effect of ice dams.<ref name="WeatherEye2007">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="srh.noaa.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Monsoons

{{#invoke:main|main}} Seasonal wind shifts lead to long-lasting wet seasons which produce the bulk of annual precipitation in areas such as Southeast Asia, Australia, Western Africa, eastern South America, Mexico, and The Philippines. Widespread flooding occurs if rainfall is excessive,<ref>Overseas Security Advisory Council (2009). Warden Message: Guyana Rainy Season Flood Hazards. Overseas Security Advisory Council. Retrieved on 2009-02-05.</ref> which can lead to landslides and mudflows in mountainous areas.<ref>National Flood Insurance Program (2009). California's Rainy Season. U.S. Federal Emergency Management Agency (FEMA). Retrieved on 2009-02-05.</ref> Floods cause rivers to exceed their capacity with nearby buildings becoming submerged.<ref>AFP (2009). Bali Hit By Wet Season Floods. ABC News. Retrieved on 2009-02-06.</ref> Flooding may be exacerbated if there are fires during the previous dry season. This may cause soils which are sandy or composed of loam to become hydrophobic and repel water.<ref>Jack Ainsworth & Troy Alan Doss. Natural History of Fire & Flood Cycles. California Coastal Commission. Retrieved on 2009-02-05.</ref>

Government organizations help their residents deal with wet season floods though floodplain mapping and information on erosion control. Mapping is conducted to help determine areas that may be more prone to flooding.<ref>FESA (2007). Flood. Government of Western Australia. Retrieved on 2009-02-06.</ref> Erosion control instructions are provided through outreach over the telephone or the internet.<ref>King County Department of Development and Environmental Services (2009). Erosion and Sediment Control for Construction Sites. King County, Washington Government. Retrieved on 2009-02-06.</ref>

Flood waters that occur during Monsoon seasons can often host numerous protozoa, bacterial, and viral microorganisms.<ref name="PreventingDisease">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Mosquitoes and flies will lay their eggs within the contaminated bodies of water. These disease-agents may cause infections of food borne and waterborne diseases. Diseases associated with exposure to flood waters include: Malaria, Cholera, Typhoid, Hepatitis A, and the Common cold.<ref name="Monsoondiseases2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Possible trenchfoot infections may also occur when personnel are exposed for extended periods of time within flooded areas.<ref>http://australianetwork.com/news/stories/asiapacific_stories_2376322.htm</ref>

Tropical cyclone

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The damage caused by Hurricane Andrew is a good example of the damage caused by a category 5 hurricane

A tropical cyclone is a storm system characterized by a low pressure center and numerous thunderstorms that produce strong winds and flooding rain. A tropical cyclone feeds on heat released when moist air rises, resulting in condensation of water vapor contained in the moist air. Tropical cyclones may produce torrential rain, high waves, and damaging storm surge.<ref name="oxfo">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Heavy rains produce significant inland flooding. Storm surges may produce extensive coastal flooding up to {{safesubst:#invoke:convert|convert}} from the coastline.

Although cyclones take an enormous toll in lives and personal property, they are also important factors in the precipitation regimes of areas they impact. They bring much-needed precipitation to otherwise dry regions.<ref name="2005 EPac outlook">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Areas in their path can receive a year's worth of rainfall from a tropical cyclone passage.<ref name="Jack2005">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> Tropical cyclones can also relieve drought conditions.<ref name=autogenerated1>National Oceanic and Atmospheric Administration. 2005 Tropical Eastern North Pacific Hurricane Outlook. Retrieved on 2006-05-02.</ref> They also carry heat and energy away from the tropics and transport it toward temperate latitudes, which makes them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth's troposphere.


Severe weather sections
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Heavy rainfall and flooding
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