Study: Rainfall Frequency Curves Must Be Updated
Engineers, climate and hydrologic scientists need to work together to update current intensity-duration-frequency curves for rainfall and flooding—used to design hydrologic infrastructure design and floodplain mapping—to ensure future infrastructure reliability, according to a new study by Daniel Wright, an assistant professor of civil and environmental engineering at the University of Wisconsin-Madison. Wright says that in many instances infrastructure has been designed to standards developed in 1961 and is already inadequate to handle more frequent flooding. There was an average of 45 10-year storms and eight 100-year storms each year across the U.S. during the 1950s. Today, there are, on average, 62 10-year storms and 12 100-year storms per year, according to the study. Wright found that 100-year storms have become 85% more common in the eastern United States over the 1950-2017 period but are only 51% more common in the western United States. Wright suggests the use of nonstationary techniques to update the standards.