New Satellite Data Indicate Increase in World Population Exposed to Floods, Makes Prediction for Africa and Asia

According to a new research in the journal, Nature, the proportion of the world’s population that is exposed to floods has grown by 24% since the turn of the century due to increased flooding and population migration.

The study, led by Cloud to Street, a global flood tracking and risk analytics company for disaster managers and insurers, researchers from the Universities of Michigan, Arizona, Columbia, Texas, Colorado, Washington, and other institutions like NASA and Google Earth Outreach, used direct satellite observations of floods to reveal that climate change and demographic changes in Southern Asia and Sub-Saharan Africa will add 25 new countries to the 32 already experiencing increasing floods. This marks an increase of population inside flood-prone regions of up to 86 million people.

“We found that economic development and people moving into flood-prone areas is significantly increasing the number of people exposed to floods in those regions. Furthermore, increasing flood exposure is rooted in underlying conditions that give vulnerable populations no choice but to settle in flood zones,” said study co-lead author Jonathan Sullivan, a postdoctoral researcher from the University of Arizona.

Safe housing alternatives for the poor and greater attention to land-use zoning will alleviate the issue.

Other key findings of the new study:

  • Fifty-eight million to 86 million people moved into observed flood regions between 2000-15; thus, there is a 20%-24% increase in the proportion of the world’s population exposed to floods.
  • 2.23 million square kilometres (~861,000 square miles) were flooded between 2000-2018, affecting between 255 million and 290 million people.
  • By 2030, the Cloud to Street model estimates that climate and demographic change will add 25 new countries to the 32 already experiencing increasing floods.
  • Despite representing less than 2% of floods, dam breaks had the highest increased incidence (177%) in the proportion of the population exposed.
  • Population growth in flooded areas is driven by people moving into flood-prone areas and economic development in those regions. As a result, vulnerable populations often have no choice but to settle in flood zones.
  • Nearly 90% of flood events occurred in South and Southeast Asia, with the large basins (Indus, Ganges-Brahmaputra, Mekong) having the largest absolute numbers of people exposed and increased proportions of the population exposed to inundation.
  • The satellite data also uncovered previously unidentified increases in flood exposure in southern Asia, southern Latin America and the Middle East.

Cloud to Street has decided to openly host the database behind the Nature study, the Global Flood Database, which the company says is the most accurate and largest observed-flood dataset ever produced. The database mapped and analysed 913 flood events in 169 countries since 2000.

According to the study, the leading causes of these flood events are heavy rainfalls, tropical storms, ice melt and dam breaks.

Satellite image showing yearly flood frequency in Niamey, Niger of West Africa. In the graphic, dark red indicates areas with the highest flood frequency. Source: Cloud to Street.

 “Using satellite observation data of floods with improved spatial-temporal resolution will help policymakers understand where flood impacts are changing and how best to adapt,” said study co-lead author Beth Tellman, chief science officer and co-founder of Cloud to Street and assistant professor at the University of Arizona School of Geography, Development, and Environment.

Most of the flood maps that nations use rely on a modelling that simulates floods based on the available ground data like rainfall and ground sensors. Still, these models are time-intensive, have significant limitations, and miss flood incidents in areas usually not prone to flooding. The Global Flood Database, on the other hand, relies on satellite observations of actual flooding events that span two decades, which allows for additional analyses of the scope, impact and trends of recent flooding.

Cloud to Street describes itself as the leading authority on remote flooding analytics. It uses satellites and artificial intelligence to monitor flood risk and to track flooding anywhere on Earth in near real-time. It combines data from more than 15 satellites and other nonconventional sources to enable governments to leapfrog legacy flood information systems and help insurers to accurately underwrite flood risk with new products such as parametric insurance.