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

SAM Satellite

Landsat 2 was launched into space onboard a Delta 2910 rocket from Vandenberg Air Force Base, California on January 22, 1975, two and a half years after Landsat 1. Originally named ERTS-B (Earth Resource Technology Satellite B), the spacecraft was renamed Landsat 2 prior to launch. The second Landsat was still considered an experimental project and was operated by NASA.
Landsat 2 carried the same sensors as its predecessor: the Return Beam Vidicon (RBV) and the Multispectral Scanner System (MSS).
On February 25, 1982 after seven years of service, Landsat 2 was removed from operations due to yaw control problems; it was offically decommissioned on July 27, 1983.

Instruments:
Return Beam Vidicon (RBV)
Multispectral Scanner (MSS)
 

Launch date:
22/01/1975

Landsat 1 was launched on July 23, 1972; at that time the satellite was known as the Earth Resources Technology Satellite (ERTS). It was the first Earth-observing satellite to be launched with the express intent to study and monitor our planet’s landmasses. To perform the monitoring, Landsat 1 carried two instruments: a camera system built by the Radio Corporation of America (RCA) called the Return Beam Vidicon (RBV), and the Multispectral Scanner (MSS) built by the Hughes Aircraft Company. The RBV was supposed to be the prime instrument, but the MSS data were found to be superior. In addition, the RBV instrument was the source of an electrical transient that caused the satellite to briefly lose altitude control, according to the Landsat 1 Program Manager, Stan Weiland.
To help understand the... read more

Launch date:
23/07/1972

Recommended Practices

SAR-based flood mapping is a standard and reliable method for determining the extent of major floods. SAR can penetrate cloud-cover, operate in any weather conditions and provide timely and crucial information about one of the most frequent and devastating natural disasters: flooding. Too often limited technical know-how separates the disaster community from the information they need; this Recommended Practice provides a near real-time, cloud-based and easy-to-use method for flood extent mapping, designed to overcome technical limitations. Without the need for downloading large and complex...
Flood hazard assessments are critical to identifying areas at risk and taking relevant preparation and mitigation measures to address the hazard. Using the HEC-RAS 2D model for preparing flood hazard maps, this Recommended Practice explains how to identify flood-prone areas and exposed infrastructure. Through its focus on the prevention and mitigation stages of the disaster management cycle, it complements the Recommended Practice on Flood Mapping and Damage Assessment with Sentinel-2, also developed by SUPARCO.

News

Image: UNOOSA.

In order for South Asian Association for Regional Cooperation (SAARC) Member States to be able to incorporate the routine use of space technology-based solutions, there is a need to increase awareness, build national capacity and develop solutions that are customized to their needs. The regional workshop and capacity-building programme on the "Role of Earth Observation in Multi-... read more

Publishing date: 12/12/2019
Regional Support Offices mentioned:
Preliminary flood map created by UN-SPIDER using Sentinel-1 radar imagery.

The 2019 rainy season in the Far North region of Cameroon has caused the Logone river to overflow and flood the Zina (Logone-et-Chari department), Maga and Kai-Kai districts (Mayo Dany) in the country's Far North region. The United Nations Office for the Coordination of Humanitarian Affairs reports that at least 60 out of 110 villages in the Zina district - 19,359 people - are affected, while 15 villages with a total of 16,215 people are affected in the Kai-Kai district.

UN-SPIDER has requested the activation of the International Charter Space and Major Disasters for the floods on behalf of the Department of Civil Protection (DPC) of Cameroon. SERTIT is acting as the project manager for this activation. An... read more

Publishing date: 19/10/2019
Flood inundation map developed using Sentinel-1 satellite data, as part of the rapid mapping response under the SERVIR-HKH Initiative at ICIMOD. Map: Kabir Uddin/ICIMOD.

In July 2019, Bangladesh, India and Nepal experienced floods and landslides during the South Asian... read more

Publishing date: 25/09/2019

Data Source

Publishing institution: Airbus Defence & Space
OneAtlas is a collaborative environment to easily access very high resolution imagery, perform large-scale image processing, extract industry specific insights and benefit from Airbus assets to develop solutions. The services include infrastructure change detection, vehicle detection & counting and will soon cover aircraft detection and land use change detection as well . Airbus provides the services through a buy-what-you-need option. It is possible to test the functionalities with a 30-days Free Trial.
Publishing institution: Geoscience Australia
The Digital Earth Africa (DE Africa) Map is a website for map-based access to spatial information. It’s is still being developed by Data61 CSIRO in collaboration with Geoscience Australia. DE Africa is leveraging international Earth Observation (EO) data and science to produce new information and services that benefit African countries. Through translating data into ready-to-use insights, more informed decisions about soil and coastal erosion, agriculture, deforestation, desertification, water quality and changes to human settlements can be made. The data is organized in data-cubes and will be fully available by 2020.

Event

Image: NASA.

Learning Objectives: 


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

  • Create a flood map using Google Earth Engine
  • Generate a map characterizing areas where landslides have occurred
  • Generate a digital... read more

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