New UN tool has been mapping floods since 1985 at street level, will aid disaster planning, especially in the Global South – World


Developed by the United Nations University with Google and other partners, the free online global flood mapping tool will help plan urban and agricultural development, effective flood defenses, disaster preparedness, identify supply chain vulnerabilities

Experts led by the United Nations University have launched a new tool that generates instant and accurate street-level resolution maps of floods around the world since 1985. Global Flood Mapping Tool will help all countries, but especially those in the South, where flood risk maps are rare and often very out of date.

Created by the Institute for Water, Environment and Health at the United Nations University in Hamilton, Canada, with support from Google, MapBox and other partners listed below, the tool enables users to adjust variables to help locate gaps in flood defenses and responses, and to plan future development of all kinds – for example, where to build or upgrade infrastructure, or expand agriculture.

Simple to use, the tool,, only requires Internet access to obtain a flood map at 30 meters resolution, street by street. A future version for more commercial uses, for example by insurance companies, will offer even more precise resolution at the building level.

The tool allows users to adjust variables to help locate gaps in defenses and flood responses, and plan future development of all kinds – for example, where to build or upgrade infrastructure, or expand agriculture.

According to Vladimir Smakhtin, Director of UNU-INWEH: “The floods of the past decade have impacted the lives of more than half a billion people, mainly in low- and middle-income countries, and caused damage of nearly US $ 500 billion, roughly the equivalent of Singapore’s GDP. More recent floods around the world have added to an increasing number of lives, damages and deaths. “

“It is estimated that 1.5 billion people, more than the European population, are at risk of being exposed to intense flooding,” adds Dr Smakhtin. “We need to prepare now for more intense and frequent flooding due to climate change and hope that this tool will help developing countries in particular to see and mitigate risks more clearly.”

Hamid Mehmood, a GIS and remote sensing specialist at UNU-INWEH who led the development of the tool, says a UNU-INWEH survey showed that a majority of flood forecasting centers in flood prone countries do not have the capacity to run complex flood forecasting models.

He adds that floods like this year in Europe that killed more than 200 people and caused billions of dollars in damage are now up to nine times more likely due to climate change.

“As temperatures continue to rise, the number of flood events will increase with their severity,” he said. “No place is immune. And yet remarkably few regions, even in wealthy countries, have useful and up-to-date flood maps due to the cost and difficulty of creating them.”

The Global Flood Mapping Tool has used the Google Earth engine combined with decades of Landsat data since 1985 – a vast catalog of geospatial data enabling analysis capabilities on a planetary scale.

Layers of Landsat information for a selected region and a specified time period identify temporary and permanent water bodies while incorporating site-specific elevation and land use data.

This produces a detailed map of flooding over the past decades, with available population, building and land use overlays, which can be used for community planning, building zoning, insurance assessments. and more.

To validate the technology, maps generated in less than a minute using the new tool were compared to documented floods in Australia, Bangladesh, Canada, Cambodia, India, Mozambique, Sri Lanka and in Thailand (detailed below), with an accuracy of 82%.

Wikipedia’s list of the deadliest floods in history (here) presents 211 events, 103 of which occurred from 1985, the first year covered by the data from the new tool.

The new tool will also reflect new floods soon after they occur to provide the most recent maps to help assess overall flood impacts and plan for the future.

“Painting a detailed picture of historic and potential areas at risk of flooding will be invaluable to any urban and regional planning service,” says project collaborator Dr Duminda Perera of UNU-INWEH.

The more detailed version of the tool under development for commercial use will provide building-by-building level resolution and integrate building occupancy data.

And a free flood risk forecasting tool, to be released next year, will use artificial intelligence to generate current and future flood risk maps for three climate change scenarios at the city, city level, district and watershed.

Maximize the efficiency of investments in public infrastructure and reduce costs

Reliable and up-to-date information on areas at risk of flooding is particularly valuable in Africa and Southeast Asia, where urban areas are expected to expand 80% by 2030. The tool can show flood-proof locations for housing and industry as well as improving overall city planning.

The new Global Flood Mapping Tool allows governments, funding agencies and disaster management authorities to focus on areas with the highest potential flood risk in the future. Knowing exactly where flooding will occur can maximize the efficiency of public infrastructure investments and reduce costs.

It differs from previously available systems in several ways, including:

-Improved the resolution of flood maps to a resolution of 30 meters, allowing city-wide analysis
-Focus on countries in the South, where data and information gaps are significant and annual flood losses are high
-Improved the accuracy of flood maps using data from multiple satellite sensors
-Improved accuracy and reduced development time for flood risk maps using AI models

Dr Mehmood adds that insurance rates related to natural disasters (where such insurance exists for homes and livelihoods affected by flooding), human and economic losses from flooding, etc., can be estimated. using the new tool.

Potential supply chain vulnerabilities can be revealed. And during disasters, the tool can be used to help determine emergency relief routes.

The Global Flood Mapping Tool could also potentially guide the development of agricultural insurance support for people living and farming at the subsistence level. The creation of this safety net would have far-reaching implications for global development goals and the promotion of safer economies and nations.

The flood maps generated by the tool can be merged with other open data sets – population density or land use / land cover changes, for example – allowing a variety of ways to look down. to come up.

The addition of other remote sensing datasets will also improve the tool and offer new ways of using it, which strengthens the capacity of countries in the South and elsewhere to better plan and respond to disasters.

* * * * *

The partners

UNESCO Madanjeet Singh Center for Water Management in South Asia, Sri Lanka

Water Resources Research and Development Center, Nepal
Planning Directorate, Bangladesh

Private sector:
Google, in-kind support as part of their Google Cloud for Researchers program
MapBox, in-kind support as part of their Education program

Civil society:
Asian Disaster Preparedness Center, Thailand
Network of Disaster Management Practitioners, Pakistan

McMaster University, Canada

International Institute of Information Technology, India

* * * * *


The following case studies were used to validate the accuracy of the new flood mapping tool:

Australia, Queensland, February 11 – 18, 2008
Bad weather and heavy rains hit Queensland’s central coast, where some rainfall stations received more than 600mm of rain in just six hours. Insurance companies spent around US $ 297 million, and repairs to road and drainage infrastructure cost around US $ 32 million.

Bangladesh, Dhaka, 2017
Three major floods affected more than 8 million people and caused loss of life, severe damage to housing, infrastructure and affected crops and livestock across the country. The flood event studied resulted from heavy rains from late March to early April, with a focus on the northeastern region of the country, where more than 850,000 households were affected and 220,000 acres of rice ready to harvest. were damaged.

Cambodia, Phnom Penh, 2011
Floods affected 18 of 24 provinces in 2011, damaged infrastructure and agriculture, threatened food security and directly affected more than 1.2 million people.

Canada, Rivière Rouge, April 2019
The Red River, which originates in Minnesota and North Dakota and flows north through Manitoba to Hudson Bay, was extensively inundated in 1950 and 2011. The study area s’ is focused on farmland and small communities between Winnipeg and the U.S. border that flooded in April 2019.

India, Bihar, April 2017
Flooding caused by excessive rainfall during the monsoon in April 2017 affected 19 districts in northern Bihar, causing 500 deaths and affecting around 17 million people

Mozambique / Malawi, March 2015
Near Mozambique’s border with Malawi, flooding in March 2015 occurred shortly after two tropical cyclones hit. More than 530,000 people have been affected, around 30,000 displaced and 37 have died. Cascading post-disaster events included a cholera outbreak that devastated already hard-hit communities

Sri Lanka, Colombo, May 2016
A tropical storm in May 2016 affected 22 of the country’s 25 districts and caused widespread flooding and devastating landslides. More than 300,000 people have been affected, including 203 listed as dead or missing

Thailand, Pathumthani and Bangkok, 2011
In 2011, Thailand recorded record rainfall during the monsoon season, immediately followed by four tropical storms in the north. The river banks burst and water discharges from upstream dams exacerbated the flooding which persisted for more than 150 days. The floods inundated over 30,000 km2 and caused an estimated US $ 900 million in losses (US $ 360 insured losses).


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