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 on the Knowledge Portal

Event

HADR logo. Image: HADR

SSTL, South East Asia Disaster Risk Insurance Facility (SEADRIF), and The World Bank will be hosting the first HADR Challenge Engagement Workshop on 26 June 2020 (FRIDAY) at 3.30PM SGT! Speak with experts to learn more about how space technology is used to aid in rescue and recovery efforts in the event of a disaster and get a peek into how SEADRIF utilises satellite data to assess the extent of damage caused by flooding.

Through this workshop, you can stand to gain further insight into what the Humanitarian Assistance and Disaster Relief challenge is about, what participants can gain out of the competition and an informative demonstration of SEADRIF’s flood monitoring software.

 

ICFM8 logo. Image: ICFM

The International Conference on Flood Management (ICFM) offers an international conference platform, hosted every 3 years, to discuss a range of flood related issues and realize significant change in a multidisciplinary, multi-sectoral area. ICFM8 aims at providing a unique opportunity to exchange ideas and experiences on a range of issues that affect flood management, particularly the need to build resilience into future planning.  The conference will identify key concerns and significant challenges of the future as currently perceived by researchers, industry, policymakers and other flood management stakeholders.

Main Conference Themes

  • Science & Technology for Flood Risk Management
  • Handling Data and Information for Flood Risk Management
  • Flood Disaster Prevention, Mitigation, and Adaptation
  • Flood Preparedness, Response, and Recovery
  • Flood Decision-making, Policy, and Governance
  • Flood Resilience... read more
Global Congress on Climate Resilience and Disaster Risk Reduction logo. Image: CEED
The major thrives of this congress will be discuss and develop an integrated Climate Resilience Ecosystem that will address Future Disaster Risk Reduction and Capacity Development of Vulnerable Communities for Sustainable & Inclusive Growth and Subsequently publish a White Paper that will be submitted to the Government of India and the State Government.
 
The Conference will discuss different topics, including:
  • Application of GIS & Remote Sensing for Integrated Disaster Risk Reduction
  • Costal Vulnerability and Adaption strategies
  • Water Security and Risk Management
  • Management of Solid Waste for Sustainable Development
  • Climate and Carbon Financing
  • Sustainability and Inclusive Growth
  • Extreme weather Events
  • Global Warming and Coastal Risks
  • Multi hazard Early Warning Systems
  • Water Resource Sustainability and Security
  • Application of GIS& RS for... read more
EO4SD webinar logo. Image: EO4SD

The European Space Agency’s Earth Observation for Sustainable Development (EO4SD) Climate Resilience Cluster is hosting a free webinar to provide insight about the potential of Earth Observation (EO) to support climate-resilient decision making at the regional and national scale.

Earth Observation (EO) data and services are vital tools for the water sector, supporting flood events, and conducting wetland inventory status in rural and urban areas. EO provides valuable information (Flood extent, historical flood events etc.) with the aim to assist authorities to prepare the most effective actions to manage flood risk and develop plans to tackle disasters. The fourth webinar of series will present in detail how Earth Observation data with different spatial and temporal resolution can contribute to flood risk, water and wetness management.

Grace webinar. Image: NASA
This lightning-style training is designed to answer the demand and interest from the applications community in technologies that can be used to support water resources management. The webinar will provide an overview of the GRACE missions, groundwater data availability, and their applications in the monitoring and management of water resources. This lightning webinar will also serve as the foundation for the upcoming advanced webinar: Using Earth Observations to Monitor Water Budgets for River Basin Management II.
 
By the end of this training, attendees will be able to:
  • Access GRACE data and analyze regional groundwater changes

Advisory Support

As part of the technical advisory support it provides to countries worldwide on accessing space-based information for disaster management and emergency response, UN-SPIDER carried out an Institutional Strengthening Mission to Lao People’s Democratic Republic from 18 to 22 March 2019 upon the request of the Ministry of Science and Technology. This activity was jointly organized by the United Nations platform for Space-based Information for Disaster Management and Emergency Response (UN-SPIDER) of the United Nations Office for Outer Space Affairs (UNOOSA) and the Ministry of Science and Technology (MOST).

Mission dates: 18/03/2019 to 22/03/2019
Regional Support Offices mentioned:

As part of the technical advisory support it provides to countries worldwide, UN-SPIDER carried out an Institutional Strengthening Mission to Myanmar from 11 to 15 March 2019 upon the request of the government. This activity was jointly organized by UN-SPIDER and the United Nations Human Settlement Programme (UN-Habitat), under auspices of the Ministry of Social Welfare, Relief and Resettle­ment (MSWRR) of Myanmar. It was hosted by the Emergency Operation Centre (EOC). 

Mission dates: 11/03/2019 to 15/03/2019

News

Satellite image over the eastern part of the Sundarbans in Bangladesh. Image: European Space Agency.

To support emergency response efforts, the International Centre for Integrated Mountain Development (ICIMOD) has mapped the extent of floods in Bangladesh following Cyclone Amphan, which caused widespread damage in the country and neighboring India in mid-May. The maps are based on Sentinel-1 radar imagery. Radar satellite data is commonly used for flood mapping purposes due to its ability to make measurements irrespective of daytime and cloud cover of the scene.

By providing an overview of the extent of inundation caused by the floods, these maps are useful in the context of disaster management, as humanitarian agencies are able to detect areas that have been affected by the floods the most and can coordinate relief and rescue activities accordingly. 

The tropical cyclone caused at least 96 deaths in Bangladesh and inflicted substantial damage to... read more

Publishing date: 09/06/2020
Sentinel-2 imagery of the area on 4 May. Image: CSSTEAP.

Using space-based information, the Centre for Space Science and Technology Education in Asia and the Pacific (CSSTEAP) affiliated to the United Nations has analysed the recent failure of a dam around the Sardoba Reservoir in Uzbekistan. Following a week of heavy rain in the region, the wall of the dam broke on 1 May and flooded surroundings in Uzbekistan as well as Kazakhstan to the north. According to media reports, the breach led to the evacuation of thousands of people in the area. 

The analysis carried out by CSSTEAP makes use of MODIS multi-temporal satellite images to identify the maximum spread of the floods, which was observed on 2 May. Waters receded in the following days, although they are still visibile along the border between the two countries on imagery from 12 May.

With the help of Landsat 8 and Sentinel... read more

Publishing date: 19/05/2020

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