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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GP-STAR factsheet

Publishing institution: International Working Group on Satellite Emergency Mapping (IWG‐SEM)

The guidelines will be reviewed and updated periodically, in order to integrate new best practices and to be responsive to evolutions in technology and end-user needs. The IWG-SEM chair has the responsibility to initiate the review, by agreement of the Working Group. 

The production and the maintenance of the guidelines are based on a joint effort by the members of the International Working Group on Satellite-based Emergency Mapping (IWG- SEM), a voluntary group of organizations involved in satellite-based emergency mapping. It was founded to improve cooperation, communication and professional standards among the global network of satellite-based emergency mapping providers. The chairperson of the group is nominated for a term of one year and is responsible for organizing the monthly telecons and bi-annual meetings. The current chair is from the Department of Geoinformatics, Z_GIS University of Salzburg / Spatial Services Ltd, Austria.

Publishing institution: United Nations Economic and Social Commission for Asia and the Pacific

Intensive capacity development sessions for Pacific island countries  (Cook Islands, Fiji, Kiribati, Micronesia (the Federated States of), Samoa, Solomon Islands, Tonga, and Vanuatu).

The project aims to enhance institutional and technical capacity for using geospatial data and technology applications and promote regional cooperation for sharing geospatial data for disaster management in Pacific island countries.

Publishing institution: United Nations Economic and Social Commission for Asia and the Pacific

Developed for the needs of the ASEAN sub-region in Asia and the Pacific, the handbooks can also be adapted for use in other regions.

The handbooks have been developed through expert working groups, in collaboration with United Nations partners including UNOOSA/UN-SPIDER, UNITAR-UNOSAT, and OCHA. As well as extensive consultation with space agencies, national disaster management authorities and regional institutions, including GISTDA, LAPAN, ASEAN Coordinating Centre for Humanitarian Assistance on Disaster Management and Asian Institute of Technology.

 

 

Publishing institution: United Nations Office for Outer Space Affairs (UNOOSA)

Vegetation Condition Index according to Kogan et al. (1990). Two-weeks normalized Differenced Vegetation Index (NDVI) composites based on 250m MODIS data are freely available for download from the MODIS/NDVI Time Series Database from the Global Agriculture Monitoring (GLAM) Project provided via the website of Geographic Department of Maryland University.

Dissemination of automatically derived flood information via a web-client (light blue: flood area; dark blue: permanent water surface). The example shows a flood situation in the eastern part of India on September 04, 2016, observed by Sentinel-1 data.
Publishing institution: German Aerospace Center (DLR)

The automatically derived flood masks are based on Sentinel-1 and TerraSAR-X radar data. TerraSAR-X data can be accessed free of cost via scientific data proposals or are provided by DLR during activations of the International Charter ‘Space and Major Disasters’. Data from Sentinel-1 is accessible free of cost via ESA’s Copernicus Open Access Hub.

Publishing institution: German Aerospace Center (DLR)

For a comprehensive and objective analysis of the settlement patterns, the DLR additionally developed an approach to display the spatial networks between the mapped settlements. It enables the computation of various form and centrality measures to characterize settlement patterns, at different spatial units, ranging from global to local scale.

Publishing institution: Copernicus Emergency Management Service (Copernicus EMS)

CEMS is a core service of the European Union’s Earth Observation programme Copernicus. It supports all phases of the disaster management cycle by delivering warnings and risk assessments of floods and forest fires and by providing geospatial information derived from satellite images on the impact of natural and man-made disasters all over the world (before, during or after a crisis). The two Mapping services of CEMS (Rapid Mapping, Risk and Recovery Mapping) are delivering products since April 2012. The Risk & Recovery Mapping provided for example information for preparedness, disaster risk assessment and risk reduction related to earthquakes in Nepal, several post-disaster assessments for flood and fire events, reconstruction and recovery monitoring in Haiti, and multi-risk assessments for the Azores Islands in Portugal. 

CEMS is coordinated by the European Commission (joint coordination between the Directorate Generals ECHO, JRC, GROW). Activation requests are... read more

Recommended Practices

As a means of emergency response after a flooding event or inland inundation, flood mapping helps to estimate the extent of the flood on a large scale. It is a basis of coordinating appropriate recovery activities, rehabilitation and prevention measures for possible upcoming events. This UN-SPIDER Recommended Practice on flood mapping and damage assessment explains the use of Sentinel-2 (S2) optical satellite data from the European Space Agency (ESA), which acquires data in 13 spectral bands. It provides hands-on practice to calculate the Normalized Difference Water Index (NDWI) to determine...
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News

Logo of the International Charter "Space and Major Disasters"

The International Charter “Space and Major Disasters” has been activated for floods in Venezuela on 15 August and in India on 16 August.

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.

The red alert for rain and flooding is set to be in place until the end of August, with further rain forecast in the coming weeks.

The Charter activation was made by Venezuelan civil protection agency “... read more

Publishing date: 16/08/2018

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