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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Event

The Asia-Pacific region faces major disaster risks in the form of earthquakes and tsunamis, tropical cyclones and typhoons, landslides, flash floods, avalanches and glacial lake outburst floods (GLOFs). Due to the large ... read more

This webinar series will build on the knowledge and skills previously developed in ARSET SAR trainings. Presentations and demonstrations will focus on agriculture and flood applications. Participants will learn to characterize floods with Google Earth Engine. Participants will also learn to analyze synthetic aperture radar (SAR) for agricultural applications, including retrieving soil moisture and identifying crop types.

Learning Objectives: 

By the end of this training, attendees will be able to: 

  1. analyze SAR data in Google Earth Engine
  2. generate soil moisture analyses
  3. identify different types of crops
Course Format: 
  • This webinar series will consist of two, two-hour parts
  • Each part will... read more
Introductory Webinar: Earth Observations for Disaster Risk Assessment & Resilience

According to a UN report1, between 1998 and 2017, the U.S. alone lost USD$944.8 billion from disasters. Between 1978 and 2017, losses from extreme weather events rose by 251 percent. It is critical to develop disaster management strategies to reduce and mitigate disaster risks. A major factor in regional risk assessment is the evaluating the of lives and property to disasters. Environmental information about disasters, their spatial impact, and their temporal evolution can plan an important role as well.

This webinar series will focus on... read more

Data Source

Publishing institution: Joint Research Center, European Commission (JRC)
GIS Malawi is a webmapper which provides various vector and raster layers covering a broad range of topics including natural hazards.

Advisory Support

Upon the request of the Ministry of Territorial Administration (MINAT), Government of Cameroon, UN-SPIDER carried out a week-long Institutional Strengthening Mission (ISM) to Yaoundé from 15 to 19 July. The mission aimed to strengthen the capacities of the Department of Civil Protection (DPC) of Cameroon in using space-based information in all phases of the disaster management cycle. It was the third UN-SPIDER mission to Cameroon after a Technical Advisory Mission (TAM) in 2011 and an Institutional Strengthening Mission (ISM) in 2012, the latter including a training course on “Remote Sensing for Disaster Management”.

Mission dates: 15/07/2019 to 19/07/2019

As part of the technical advisory support it provides to countries worldwide, UN-SPIDER carried out an Institutional Strengthening Mission to Nepal from 17 to 21 December 2018 upon the request of the government. The mission was a follow-up activity to the Technical Advisory Mission (TAM) to Nepal in July 2017 that assessed use of space-derived information in all aspects of disaster management and offered recommendations and action plan to strengthen the disaster risk management and emergency response in the country. The TAM and ISM were conducted with support from the Ministry of Home Affairs (MoHA). The Nepal GIS Society also offered support in organizing the programme.

Mission dates: 17/12/2018 to 21/12/2018

News

Mission team with the director and staff of the Department of Civil Protection and other organizations. Image: DPC.

Upon the request of the Ministry of Territorial Administration (MINAT), Government of Cameroon, UN-SPIDER carried out a week-long Institutional Strengthening Mission (ISM) to Yaoundé from 15 to 19 July. The mission aimed to strengthen the capacities of the Department of Civil Protection (DPC) of Cameroon in using space-based information in all phases of the disaster management cycle. It was the third UN-SPIDER mission to Cameroon after a Technical Advisory Mission (TAM) in 2011 and an Institutional Strengthening Mission (ISM) in 2012, the latter including a training course on “... read more

Publishing date: 22/07/2019
Regional Support Offices mentioned:
Modeled catchment mean annual loss. For clarity, only catchments with a mean annual loss of >$1.5 million have been plotted. Image: Quinn, N., Bates, P. D., Neal, J., Smith, A., Wing, O., Sampson, C., et al. ( 2019).

A recent study, published in the Water Resource Research journal, presents a new method for a spatially realistic national flood risk assessment.

Researchers expanded an existing statistical model, based on U.S. Geological Survey (USGS) river flow data, to simulate a thousand years of potential flood events. By calculating the damage for each event in dollars, they were able to estimate the probability of the United States suffering particular annual flood damages.

Traditional risk flood analysis models assume that the impacts on the entire flood-affected... read more

Publishing date: 04/07/2019
Damage from a 7.4 earthquake and a tsunami that hit the Indonesian island of Sulawesi on 28 September 2018. Image: European Union/Pierre Prakash/Flickr.

In the past year, “there were 315 natural disaster events recorded with 11,804 deaths, over 68 million people affected, and US$131.7 billion in economic losses around the world.” This is according to the Centre for Research on the Epidemiology of Disasters (CRED) in its recently released 2018 Natural Disasters Report

While these 2018 natural disaster values represent a decrease when compared with the annual averages from 2008 to 2017, some geographic areas still experienced great losses of life and damages due to natural hazards. Indonesia was most adversely impacted in terms of lives... read more

Publishing date: 01/07/2019

Recommended Practices

Storm surges and tidal waves are global phenomena that considerably affect human populations in coastal and island regions. According to the Guide to Storm Surge Forecasting published by the World Meteorological Organization in 2011, storm surges can be defined as “oscillations of the water level in a coastal or inland body of water in the time range of a few minutes to a few days, resulting from forcing from atmospheric weather systems. According to this definition, the so-called wind waves, which have durations on the order of several seconds, are excluded”. Storm surges are a coastal...

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