Flood

This Copernicus Sentinel-1 image combines two acquisitions over the same area of eastern Iraq, one from 14 November 2018 before heavy rains fell and one from 26 November 2018 after the storms. The image reveals the extent of flash flooding in red, near the town of Kut. Image: modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO.

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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News

UN-SPIDER and its Regional Support Office in Nigeria, the National Space Research and Development Agency (NASRDA), conducted an online training on the UN-SPIDER Recommended Practice on Flood Mapping and Damage Assessment Using Sentinel-1 SAR Data in Google Earth Engine. Staff from NASRDA as well as from the National... read more

Publishing date: 24/10/2020
Regional Support Offices mentioned:
Participants at the virtual expert meeting. Image: UNOOSA.

In order to discuss and promote the use of space technologies in addressing natural hazards such as forest fires and landslides in Latin America, UN-SPIDER conducted a virtual regional expert meeting on the topic of “Space-based Solutions for Disaster Risk Reduction and Emergency Response in Latin America” from 22 to 24 September 2020. The meeting was jointly organized with UN-SPIDER Regional Support Offices from Argentina (National Space Activities Commission, CONAE), Brazil (Federal University of Santa Maria, UFSM), Colombia (Geographic Institute Agustin Condazzi, IGAC), and Mexico (Mexican Space Agency, AEM).

In Latin America, UN-SPIDER and its Regional Support Offices have regularly carried out regional expert meetings, training courses and other joint efforts since 2011. The last Regional Expert Meeting took place in 2017 in Mexico.

The meeting, which consisted of three two-hour-long sessions, brought together a total of over 200... read more

Publishing date: 28/09/2020
A SpaceX Falcon 9 rocket launches the SAOCOM 1B satellite. Image: Manuel Mazzanti/CONAE

The Argentinean SAOCOM 1B satellite was successfully launched into orbit on 30 August 2020. Developed by the National Argentinean Space Commission (CONAE), this new satellite will join SAOCOM 1A and four Italian COSMO-SkyMed to complete the joint Italian-Argentinean Satellite System for Emergency Management (SIASGE). Like its predecessor, SAOCOM 1B was built in Argentina through a joint effort with private companies and universities. It will operate at an elevation of 620 kilometers above the surface of the Earth. A SpaceX Falcon 9 booster launched the satellite from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, United States of America.

The SAOCOM 1B satellite has been fitted with a Synthetic Aperture Radar (SAR) sensor that makes use of microwaves in the electromagnetic L-band, which goes through clouds... read more

Publishing date: 14/09/2020
Regional Support Offices mentioned:
Tropical cyclone Fani over the eastern coast of India on 2 May 2019. Image: NASA.

According to the latest issue of an annual disaster statistics report, floods were the deadliest type of disasters in 2019, followed by extreme... read more

Publishing date: 20/08/2020
Floods in Bangladesh in 2019. Image: UN Women Asia and the Pacific.

The International Centre for Integrated Mountain Development (ICIMOD) is leveraging space-based information to support government and humanitarian agencies in the Hindu Kush Himalayan (HKH) region with timely information for flood early warning and inundation mapping. The efforts, which consist of developing a streamflow prediction system for flood early warning and of providing near real-time flood maps for disaster... read more

Publishing date: 19/08/2020
Areas flooded and damaged following cyclone Idai, northwest of Beira. Image: European Union/Christian Jepsen.

In recent years, Mozambique has suffered severe floods and droughts that have impacted urban and rural communities throughout the country. In the March and April 2019, tropical cyclones Idai and Kenneth triggered major floods in Mozambique, Malawi, Zimbabwe, and Comoros.  The Port of Beira was hard hit, as cyclone Idai destroyed transmission lines and bridges, leaving the port without access to these lifelines for several days.   In contrast the powerful El Niño event of 2016 triggered major droughts that affected most of the country. Thousands of farmers lost their crops and their cattle and had to rely on humanitarian assistance to cope with the impacts of this event.

Taking... read more

Publishing date: 10/08/2020
Regional Support Offices mentioned:
Field Work on Ogunpa flood plain Ibadan, Nigeria. Image: GMES.

Floods are among the most frequent natural hazards around the world, as well as in Africa, and can trigger devastating disasters among the most vulnerable communities. Climate change, and inadequate land-use/land-cover changes can exacerbate this situation and may erode hard-won gains in many developing countries. The first step to reduce the impacts of such floods is to understand the dynamics of floods throughout the floodplains more precisely.

To support an improved understanding of floods in West Africa, the Centre for Space Science and Technology Education (CSSTE) is leading the project entitled Multi-Scale Flood Monitoring and Assessment Services for West Africa (MiFMASS) that relies on... read more

Publishing date: 10/08/2020

Event

Participants at the virtual expert meeting. Image: UNOOSA.

En décadas recientes muchas comunidades en América Latina y el Caribe han experimentado desastres ocasionados por inundaciones, sequías, deslizamientos, terremotos, erupciones volcánicas y maremotos o tsunamis que han erosionado los logros asociados a procesos de desarrollo. Además, en este año 2020 la pandemia ocasionada por el virus COVID-19 ha impactado a muchos países del mundo, forzando a los gobiernos, al sector privado, a la sociedad civil y a organismos regionales e internacionales a modificar sus planes de trabajo. De manera paralela, varios países del Este de África, del Sudoeste de Asia y de América Latina están experimentando los impactos de la plaga de langosta.  

Convencidos que las tecnologías espaciales pueden jugar un papel preponderante en apoyar los esfuerzos que llevan a cabo las instituciones en materia de gestión para la reducción de riesgos, la preparación, la respuesta y la recuperación en caso de desastres; la Asamblea General de las Naciones Unidas... read more

Image: UFSM.

The Federal University of Santa Maria of Brazil (UFSM), in its role as a UN-SPIDER Regional Support Office (RSO), and UN-SPIDER joined forces to conduct a virtual seminar on the use of the UN-SPIDER Recommended Practices to process satellite imagery to map the geographic extent of floods, and to elaborate a series of maps that allow government agencies, as well as regional and international organizations, to assess the severity of droughts in particular years in comparison to droughts in other years. The webinar, conducted on 4 August 2020, brought together more than 30 officers of government agencies of Mozambique, as well as researchers, faculty members and students from various universities.

During the event, researchers from UFSM made participants aware of efforts by the... read more

Regional Support Offices mentioned:

Synthetic Aperture Radar (SAR) data can be acquired day and night, even in cloudy conditions, providing a dense time-series suitable for trend analysis and change detection.  Environmental applications for SAR data include:

  •     forest inventory, biomass estimation and condition monitoring
  •    ... read more

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