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

Noticias

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 Earth... 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. 

ESCAP has published two additional reports this year, one on the “Impact and Policy Responses for COVID-19 in Asia and the Pacific”, which presents an initial assessment of the COVID-19 pandemic in Asia and sub-regional... read more

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

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

As a follow-up to the two preceding advisory support missions to the Dominican Republic, in 2010 and 2011, UN-SPIDER conducted an Institutional Strengthening Mission and organized a one-week training course to strengthen the remote sensing capacities of the inter-institutional Geo-Spatial Information Team for Risk Management to derive flood-related information from satellite imagery. The training course was organized with the National Emergency Commission and three regional support offices: IGAC, CATHALAC and CONAE and took place from 13 to 17 May 2013.

Mission dates: 13/05/2013 to 17/05/2013

From 12 to 16 May 2013, as a follow-up to the UN-SPIDER technical advisory mission to Bangladesh in 2011, UN-SPIDER conducted a Institutional Strengthening Mission and organized a capacity-building programme on the topic of space technology for flood hazard mapping, flood forecasting and rapid mapping in Bangladesh. The programme was jointly organized with the Comprehensive Disaster Management Programme of the Ministry of Disaster Management and Relief.

Mission dates: 12/05/2013 to 16/05/2013

UN-SPIDER conducted a Institutional Strengthening Mission in Sri Lanka from 24 to 28 April 2017. Th ISM was a follow-up to the technical advisory mission to Sri Lanka in 2011. Both the original mission and the follow-up activity were hosted by the Ministry of Disaster Management of Sri Lanka and its associated Disaster Management Centre.

Mission dates: 24/04/2017 to 28/04/2017

Evento

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... read more

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