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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    As of 31 March 2012, 49 evacuation centers (of which 31 schools) with in total more than 3700 people, approximately half of which are children, have been operational in Ra (4), Tavua (5), Ba (14), Lautoka (10), Nadi (8) and Sigatoka (8).The situation is considered worse than the recent flooding in January 2012,as more areas are flooded. Deterioration of the situation can be expected as further weather systems accompanied by heavy rains are expected to affect Fiji.

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  • Namibia's President Pohamba declares floods emergency

    Namibia's President Hifikepunye Pohamba has declared a state of emergency following serious flooding in the north of the southern African country.

    More than 20 people are reported to have drowned and some 10,000 displaced, many from the town of Oshakati.

    The BBC's Frauke Jensen in the capital Windhoek says livestock have been lost, crops destroyed and roads washed away.

    There has been heavy rainfall since January, causing water levels to rise in the Zambezi and Okavango rivers.

    Two years ago, more than 90 people were killed by floods in Namibia.

    Source: http://www.bbc.co.uk/news/world-africa-12913487

    The flood already exceeds the 2009 flood, which was then considered to be the highest in known history. Reports from upstream (Angola) indicate that more water is expected and the Namibian Meteorological Services predicted more rains next week.

     


    Contacts

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Term Parents

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