Flood

Definition

Flood is usually used as a general term to describe the overflow of water from a stream channel into normally dry land in the floodplain (riverine flooding), higher-than–normal levels along the coast and in lakes or reservoirs (coastal flooding) as well as ponding of water at or near the point where the rain fell (flash floods) (IRDR Glossary).

Facts and figures

Floods are the natural hazard with the highest frequency and the widest geographical distribution worldwide. According to the Organization for Economic Cooperation and Development (OECD)  flooding is one of the most common, widespread and destructive natural perils, affecting approximately 250 million people worldwide and causing more than $40 billion in damage and losses on an annual basis (OECD).

Flooding occurs most commonly from heavy rainfall when natural watercourses lack the capacity to convey excess water. It can also result from other phenomena, particularly in coastal areas, by a storm surge associated with a tropical cyclone, a tsunami or a high tide. Dam failure, triggered by an earthquake, for instance, will lead to flooding of the downstream area, even in dry weather conditions.

Various climatic and non-climatic processes can result in different types of floods: riverine floods, flash floods, urban floods, glacial lake outburst floods and coastal floods.

Flood magnitude depends on precipitation intensity, volume, timing and phase, from the antecedent conditions of rivers and the drainage basins (frozen or not or saturated soil moisture or unsaturated) and status. Climatological parameters that are likely to be affected by climate change are precipitation, windstorms, storm surges and sea-level rise (UNDRR).

When floodwaters recede, affected areas are often blanketed in silt and mud. The water and landscape can be contaminated with hazardous materials such as sharp debris, pesticides, fuel, and untreated sewage. Potentially dangerous mold blooms can quickly overwhelm water-soaked structures. Residents of flooded areas can be left without power and clean drinking water, leading to outbreaks of deadly waterborne diseases like typhoid, hepatitis A, and cholera (UNDRR).

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Related content on the Knowledge Portal

  • Continuouce heavy rain in the catchment area of Pursat River from 11 Oct 2010 caused flash flooding along the Pursat River. Thousands of people are affected and the flooded land including Pursat City inundated widely.

    Source: GLIDEnumber

  • The island of Saint Lucia has for the last two weeks been experience a heavy downfall of rain which has resulting in some flash flooding in the city of Castries and other parts of the island. However on Wednesday October 6, 2010 the central and eastern part of the island which encompasses the communities of Micoud, the Dennery Valley and Dennery Village experienced heavy rainfall in the early morning hours ending at about 9:00am.The heavy rainfall resulted in flooding in the Dennery Valley and Village thus affecting vehicular access to the community via the East Coast Highway for more than 5hrs.

    Source: www.glidenumber.net

  • More than 30,000 people are currently homeless in Benin and at least 7,000 hectares of crops are destroyed as a result of flooding. The most affected areas are So-Ava, Cotonou (1st, 2nd,3rd,6th and 9th Arrondissements) and Karimana communes. Indeed, unusually heavy rainfall during this rainy season with more forecasted over the next 3 days, the waters of the rivers Niger and Ouémé experienced unusually rapid rise, overflowing their banks to cause flooding in most parts of the country. The priority area of interest is the south and covers So-Ava Commune, Cotonou and Dangbo Commune.

    Source: http://rescommunis.wordpress.com/2010/10/08/disasters-charter-activated-flood-in-benin/

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  • Thirteen people were killed and dozens were missing after flash floods smashed through a district in eastern Indonesia's Papua province.

    Source: www.glidenumber.net

  • Te Ministry of Disaster Management reports that over 2000persons affected and 75 house destroyed by pre- monsoon rains.

    Source: GLIDEnumber

  • HA NOI - Torrential rains brought flooding and landslides to the country's central region, killing at least six people and injuring two.

    Source: GLIDEnumber, Vietnam News

  • At least 63 people have been killed from flooding and landslides in northern India. Authorities have evacuated about 5,000 people to safety from Uttarakhand state.

    Source: GLIDEnumber

  • Floods have displaced nearly 60,000 people in the last month in south Sudan with many at risk of malaria and other diseases.The assessment committee's report states that some 250 families covering 2470 people were affected by the flash floods. It is also reports that 176 families in Panthou have been displaced during the 24 hour torrential downpour that hit part of greater Aweil South County.

    Sources: www.alertnet.org, www.reliefweb.int

     


    Status Update: 15/09/2010


    Contacts:

    UNOOSA/UN-SPIDER

    Email: un-spider [at]

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  • On 5 and 6 September 2010 torrential rain recorded 202.6mm which is 20% of total rainfall normally received by the country. The rainfall caused floods almost nationwide affecting over 25,000 people by destroying their residences, and other basic livelihoods. On 7 September 2010, the Government of the Gambia declared a State of National Disaster due to the magnitude and complexity of the floods.

    Source: www.glidenumber.net

  • Torrential rain from 19 to 21 August 2010 led to the flooding of 8 regions affecting 38 communities. The collapse of houses has led to the displacement of over 1,000 families.

    Source: GLIDEnumber

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