Three-quarters of people living in river deltas not protected from floods

River deltas worldwide are densely populated. Some of these areas have been leveed, but most are not protected from flooding. According to research by Utrecht University and others, only 17 percent of global deltas are well protected, and more than 100 million people live outside protected areas.

Global database

The researchers mapped levees in over 150 deltas, finding more than 10,000 levees. Levees can give a false sense of security, which actually increases the risk of flooding, we saw during hurricane Katrina, says Jaap Nienhuis , researcher at Utrecht University and lead author of the study. Data on these deltas and levees is important for, among other things, proper flood risk assessment, especially taking into consideration future sea level rise.

The database of major deltas we have now created is the most comprehensive one yet.

Jaap Nienhuis

Until now, deltas and their levees have been difficult to map globally, which has also made calculating flood risks difficult. This is because the locations and quality of levees worldwide are recorded in different ways; many historical levees, for example, are only recorded on paper. Many national data are also not publicly available, mainly for safety reasons, Nienhuis explains.

The database of major deltas we have now created is the most comprehensive yet, and can be used by both researchers and policymakers to better assess flood risk.

Check out the database


Nienhuis, J. H., Cox, J. R., O’Dell, J., Edmonds, D. A., and Scussolini, P.: A global open-source database of flood-protection levees on river deltasá(openDELvE), Nat. Hazards Earth Syst. Sci., 22, 4087-4101,­-4087-2022 , 2022.