It has long been thought that wealthy countries, bolstered with more money for infrastructure investment, face lower risks of flooding.

But new research Thursday found that rich countries face major risks as climate change and human activity render coastal populations increasingly vulnerable to devastating river delta floods. Though wealthy nations have greater resources to protect against flooding such as dams, climate change could increase the frequency and severity of floods and storms to a level that those nations may be challenged to keep pace with due to costs, according to a study in the US journal Science.

Man-made changes are also increasing the risk that coastal communities face, the study found. As more land is used for agricultural production, for example, erosion occurs that reduces natural protections against flooding, the research found.

The researchers calculated the challenges that more than 340 million people could face in 48 major coastal delta river communities around the world. The researchers flagged the Mississippi and the Rhine delta as potentially vulnerable, and said in some cases, the risk multiplied by four or eight times.

The study said infrastructure is key to preventing flooding and recommended that wealthy nations make wise investments now. “Economic ability and decisions to deploy engineering solutions will be key factors in determining how sustainable deltas become in the long term,” the study said. In an editorial also published in Thursday’s issue of Science, researchers Stijn Temmerman of the University of Antwerp and Matthew Kirwan, from the Virginia Institute of Marine Science said coastal communities need to devise strategies to mitigate flood risks.

One option is to restore sediment to delta plains though ecosystem-based engineering projects. They devised a model for New Orleans and coastal Louisiana and said building or preventing the loss of more than 500,00 hectares of wetlands could reduce annual flooding damage by $5.3 to $18 billion over 50 years. Recent data estimated that by 2050, if the sea level continues to rise at its current rate, more frequent flooding could cost up to $1 trillion annually, causing serious damage to the 136 largest coastal cities in the world.