Inundación

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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    Floods in Venezuela

    In Venezuela, persistent heavy rain and swollen rivers have caused severe flooding, which has affected over 10,000 people in the Venezuelan provinces of Amazonas, Apure, Bolivar and Anzoategui. The Orinoco river reached its highest levels in 40 years, leading the river to burst its banks in my places. Local authorities have set up an aerial bridge over the river so supplies of food, medicine and aid can reach the affected populations. Major arterial roads have also been closed, isolating some areas and further hampering emergency response efforts.

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    27/07/2018
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    Emergency responders are working to rescue people from the area, evacuate them to emergency shelters and search for the missing. Local authorities have also appealed to government bodies and other communities to provide emergency aid such as clothing, food, drinking water and medicine.

    The International Charter was jointly activated by the United Nations Office for Outer Space Affairs (UNOOSA) and the United Nations Institute for Training and Research (UNITAR) Operational Satellite Applications Programme (UNOSAT) for major floods in Lao People's Democratic Republic on 24 July 2018. UNOOSA activated the Charter on behalf of the country's...
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  • The International Charter “Space and Major Disasters” was activated on 7 July for a major flooding disaster which has hit Japan, the worst the country has experienced in 36 years.

    Heavy rains, which first started at the end of June 2018, caused flash flooding and deadly landslides across western and central Japan from 5 July. Over 200 fatalities have been recorded in the country so far as a result of the disaster. The rains which caused the flooding appear to have been caused by warm, humid air flowing from the Pacific Ocean and by remnants of Typhoon Prapiroon, both of which intensified the seasonal rain front. Some 8.63 million people across 23 prefectures in Japan have been...

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    The agreement allows CWC to make use of Google’s artificial intelligence, machine learning and geospatial mapping expertise for effective water management and flood forecasting. The agreement will also help CWC to better disseminate flood related information through different platforms developed by Google. 

    Under this Agreement, CWC and Google will share technical expertise in different fields related to flood management, including  geospatial flood mapping and analysis of hydrological observation data. The agreement also facilitates collaboration on improving flood prediction systems, which will help provide location-targeted, actionable flood warnings; a high priority research project utilizing Google Earth Engine to help...

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    10/07/2018
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    Cyclone Mekunu brought severe rainfall and winds causing flooding in areas of Yemen as it made landfall on 25 May. Local reports suggest that at least seven people have been killed and over 1,000 families have been displaced due to the flooding. The cyclone and floods have also damaged infrastructure and agricultural equipment in many districts of the Yemeni mainland. Some 120 fishing ships have reportedly been lost to the cyclone and a search is ongoing for missing fishermen.

    One of the worst affected areas is the Yemeni island of Socotra in the Arabian Sea. Residents on the island are fleeing from torrential floods and more than 30 people are reported missing. Smaller islands off the coast of Socotra have also been heavily impacted and there is growing concern for the 2,500 families living on the islands of Abd Al Quri and Samhah as...

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  • The International Charter Space and Major Disasters has been activated for flooding in Djibouti on 20 May and Sri Lanka on 21 May 2018.

    In Djibouti, tropical cyclone Sagar caused flash floods across the country, impacting up to 30,000 people according to authorities. The United Nations Institute for Training and Research's (UNITAR) Operational Satellite Applications Programme (UNOSAT) requested the activation on behalf of the United Nations Office for the Coordination of Humanitarian Affairs (UNOCHA). UNOSAT is acting as the project manager for the activation.

    In Sri Lanka, monsoon rains have claimed the lives of eight people and have left a further 172 requiring emergency assistance. Rain and winds have closed roads, interrupted power lines and displaced many people. With the continuation of heavy rains, landslides also became an issue.

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    More than half the annual rainfall in the American Southwest falls in the form of the unpredictable downpours during the North American monsoon season. Whilst monsoon precipitation is essential for the ecosystem of the region, the torrential rain often causes flash flooding and hence poses a risk to life and property. Technology that aids the accurate forecasting of these rains is therefore of paramount importance.

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UN-SPIDER Regional Support Offices with hazard-specific expertise