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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Noticias

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
Report cover page. Image: UNESCAP.

The United Nations Economic and Social Commission for Asia and the Pacific (ESCAP) has published a policy study concerning the impending climate risk scenarios in South Asia and their intersection with the COVID-19 pandemic. The aim of this report is to facilitate policy actions that could protect communities at risk as well as to lay the foundations of resilient recovery of the most vulnerable in South Asia. 

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Publishing date: 23/07/2020
Image: UNFPA.

In the latest example of anticipatory humanitarian action, the United Nations released $5.2 million from the Central Emergency Response Fund (CERF) to help communities in Bangladesh prepare themselves ahead of major monsoon floods. The allocation of funds to agencies in the country to prepare to deliver support was triggered by a forecast from the Global Flood Awareness System (GloFAS), which predicted areas having a greater than 50 per cent chance of experiencing a severe flood between 14 and 16 July. Following a second forecast by the Government’s Flood Forecasting & Warning Centre (FFWC) on 11 July, aid workers began distributing the aid.

The swift assistance provided in Bangladesh comes as United Nations Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator Mark Lowcock has agreed to allocate up to $140 million from the UN... read more

Publishing date: 21/07/2020

Evento

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

Data Source

Advisory Support

As a follow-up to the recommendations of the technical advisory mission to Mozambique conducted in October 2012, UN-SPIDER conducted a Institutional Strengthening Mission and jointly with UNDP-Mozambique organized a national training course on disaster mapping using space technology in Maputo. The course took place at the Eduardo Mondlane University.

Mission dates: 04/11/2013 to 08/11/2013

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