USGS Scientists Study Shows Potential Link Between C02 Levels, Size of Floods

A new report published by U.S. Geological Survey (USGS) scientists in the Hydrologic Sciences Journal looks at the potential link between the amount of carbon dioxide in the atmosphere and the size of floods over the past century. Using historical records of floods throughout the United States, scientists studied flood conditions at 200 locations across the country, looking back 127 years through 2008.

Only one of four large U.S. regions showed a significant relationship between carbon dioxide in the atmosphere and the size of floods over the last 100 years. In the Southwest, floods have become smaller as carbon dioxide has increased.

This does not mean that no strong relationship between flooding and greenhouse gases will emerge in the future, says USGS. An increase in flood magnitude remains one of the most anticipated impacts of climate change, and land and water resource managers are asking how to estimate future flood risks and develop effective flood mitigation strategies for the future.

“Currently we do not see a clear pattern that enables us to understand how climate change will alter flood conditions in the future, but the USGS will continue to collect new data over time and conduct new analyses as conditions change,” said USGS scientist and lead author of the study Robert Hirsch. “Changes in snowpacks, frozen ground, soil moisture and storm tracks are all mechanisms that could be altered by greenhouse gas concentrations and possibly change flood behavior. As we continue research, we will consider these and other factors in our analyses.”

The decrease of floods in the Southwest region is consistent with other research indicating the region has been getting drier and experiencing less precipitation as a likely result of climate change.

"The relationship between greenhouse gas concentrations and floods is complex, demonstrating the need for long-term streamflow data to help guide future flood hazard mitigation and water resources planning," said Matthew Larsen, USGS associate director for climate and land use change. "USGS streamgages provide real-world data to help scientists understand this relationship. Planning for water supplies and flood hazards should be informed by a combination of predictive modeling approaches as well as statistical approaches such as this study."

Source: U.S. Geological Survey