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

  • Heavy rains caused flooding in 40 districts surrounding the Kur (Kura), Azerbaijan's main river. 20,000 homes have been flooded, 300 of them ruined, and 2,000 fell into disrepair. 50,000 hectares of cultivated land and pasture are under water.

    Source: GlideNumber

  • The torrential rains of 7 May, 2010, caused floods and mudslides in Tajikistan. In total 10 districts were affected in the south regions, of wich Vose, Muminabad, Temurmalik, Baljuvon and Shurabad districts and Kulyab town of Kulyab region, as well as Nurek, J. Rumi, Yovon and Jilikul districts of Kurgan-tube region. According to the preliminary data received from RCST regional branches, the average number of disaster affected residencies in both regions is some 1059 houses (or 6354 people), out of which 179 houses totally destroyed. On the report of RCST staff and volunteers 60 people were killed, but at this stage only 13 people officially reported by the government, 40-50 are missing, 40 hospitalized and 85 injured.

    Source: GlideNumber

     


    Available Space-based Information for: Floods in Tajikistan (May 7 - ongoing) 

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  • Rainfall and torrential flooding in western province of Herat has devastated many areas, killing some 14 people, including seven children, injuring 30 others, damaging more than 250 houses and destroying around 300 hectares of agricultural land.

    Source: GlideNumber

  • Since March 1st 2010, the long rains have been pounding most parts of Kenya resulting in flood situations in parts of the Kenya.
    The floods have claimed 56 lives country wide; over 9,135 house holds have since been displaced and over 90,000 persons affected.
    As a result of the incident rains and run-off water from the Ethiopian highlands at the Kenya Ethiopia border have resulted in widespread floods in the vast district. The Ethiopian side has also issued a flood warning for the Kenyans living in the shadow of Wirwita dam in Ethiopia since the dam is about to reach overspill level. As a result, over 1000 families have evacuated from the projected course of the waters from Wirwita dam.


    Due to the vastness of Garissa district, limited GSM coverage, impassable roads, and the exorbitant costs of and limitations of chartering airplanes or choppers for aerial assessment and the prevailing humanitarian case the Emergency Operations Center (EOC) of Kenya Red Cross Society…

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  • The Caprivi region, particularly those constituencies traversed by the Zambezi and Chobe rivers which are Kabbe and Katima Rural have experienced high water flows arising from Zambia causing severe flooding.

    Source: GlideNumber

  • Hundreds of families affected by floods caused by heavy rains that started with the beginning of the winter (rainy) season

    Source: GlideNumber

    The Colombian Red Cross said Wednesday that 3,000 families across the country have been affected the floods, landslides and high winds that have battered the country in the last two weeks, according to Caracol Radio.

    The central Colombian department of Risaralda was battered with heavy rains and gail force winds over Easter, leaving 80 families homeless.

    Most of the damage was in the departments of Antioquia, Cauca, Choco and Caqueta Quindio, but the Red Cross said that the families struggling to deal with the devastation were spread over twelve departments.

    The Red Cross has called on local authorities to implement permanent systems to monitor the levels of river and streams and the conditions of hillsides…

    read more
  • As a result of heavy rains on 11 April 2010, rural areas of Tajikistan have been affected by flooding and landslides. Around 18 villages throughout the country have been affected. In total 319 houses (with 1,914 inhabitants) have been damaged, out of which 5 houses totally destroyed. Two people were killed by the floods.

    Source: GlideNumber

  • A sharp increase in the temperature from minus 10 degrees to plus 10 degrees Celsius triggering the melting of snow caused floods between 22 and 26 March, inundating seven settlements in four municipal districts in the Volgograd region of the Russian Federation. Some 3,250 people, including 197 children were affected and had to be evacuated into temporary shelter solutions

    Source: GlideNumber

  • Areas affected by Cyclone Aila have been hit by flooding and swollen rivers due to high tides. Over 45,000 are marooned, 28 villages inundated.

    Source: GlideNumber

  •  Torrential rains caused floods and landslides that killed at least 31 people in Rio de Janeiro state, shutting down transport and commerce.

    Source: GlideNumber

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