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).

Related content

Event

The Global Flood Partnership is a multi-disciplinary group of scientists, operational agencies and flood risk managers focused on developing efficient and effective global flood tools that can address these challenges. Its aim is to establish a partnership for global flood forecasting, monitoring and impact assessment to strengthen preparedness and... read more

Flood Risk Management is by definition dealing with uncertainty. Floods occur often enough, but the timing and location of flood events are uncertain, and so is the response of society. But the concepts and methods of flood risk analysis and management are progressively tuned to deal with this kind of uncertainties.

This challenge of scientific innovation and practical adaptation is too big for the current generation of scientists and practitioners. FLOODrisk2020 is therefore committed to attract, coach and listen to the next generation of scientists and practitioners who... read more

This webinar focuses on Flood History and - Risk as well as on Land Motion (subsidence), but related topics that will be touched upon are LU/LC and Change, Transport Infrastructure and Green Urban areas, as these are also relevant for assessing sustainability of cities with respect to Climate Resilience and... read more

Course aimed to discover how continental water and ice masses are measured and monitored through... read more

From 22 to 26 July 2019, the training course on Integrated Flood Risk Management (IRFM) will introduce practitioners to the key concepts of IRFM. The course is organized by and held at the Asian Disaster... read more

Data Source

Publishing institution: Nigeria National Space Research and Development Agency (NASRDA)
This interactive portal provides near real time data on potential floods that will potentially affect countries in West Africa. The data has a maximum of 10 day forecast and includes flood categories 2-year, 5-year, and 30-year return periods.

GP-STAR factsheet

Schematic Workflow for the derivation of an exemplary Sendai indicator using crisis information generated from satellite remote sensing (Source: own figure; Copernicus Emergency Management Service (©European Union), EMSN024, EMSN056)
Publishing institution: German Federal Office of Civil Protection and Disaster Assistance

To meet the global challenges, the United Nations adopted several framework agreements, including the Sendai Framework for Disaster Risk Reduction at the Third United Nations World Conference on Disaster Risk Reduction (2015-2030). The framework builds the international reference point for disaster preparedness and focuses on... read more

News

Image of South Africa acquired on 19 June 2010 by ESA's Envisat satellite. Image: ESA, CC BY-SA 3.0 IGO.

The United Nations Office for Outer Space Affairs, through its UN-SPIDER programme, has activated the International Charter "Space and Major Disasters" on behalf of the National Disaster Management Centre (NDC) of South Africa for the recent floods and mudslides in the country. The German Aerospace Centre (DLR) is acting as project manager for this activation.

Heavy rainfall has been affecting eastern South Africa over the past few days, causing floods and landslides in Durban and the surrounding KwaZulu-Natal province. According to media reports,... read more

Publishing date: 26/04/2019

As part of the technical advisory support it provides to countries worldwide in making use of space-based information for disaster management, UN-SPIDER carries out an Institutional Strengthening Mission to Ecuador from 8 to 12 April 2019 upon the request of the Government of Ecuador. This activity is jointly organized by the United Nations Office for Outer Space Affairs (UNOOSA), through its United Nations Platform for Space-based Information for Disaster Management and Emergency... read more

Publishing date: 08/04/2019

Advisory Support

As part of the technical advisory support it provides to countries worldwide, UN-SPIDER carried out an Institutional Strengthening Mission to Republic of Ecuador from 8-12 April 2019 upon the request of the government. This activity was jointly organized by the United Nations Office for Outer Space Affairs (UNOOSA), through its United Nations Platform for space-based information for disaster management and emergency response (UN-SPIDER) and the National Risk and Emergency Management Service of Ecuador. The Military Geographic Institute of Ecuador, the Agustín Codazzi Geographic Institute of Colombia (IGAC) and the Federal University of Santa Maria, Rio Grande do Sul, Brazil supported the mission.

Mission dates: 08/04/2019 to 12/04/2019

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