Research is ensuring stormwater systems are designed for the future

Apr 23, 2012

In a world of changing weather and rainfall patterns, engineers face challenges when designing stormwater management systems.

A Kansas State University team is researching how climate change is affecting rainfall and weather patterns throughout Kansas to help with future adaptation and . The research team, led by Stacy Hutchinson, associate professor of biological and agricultural engineering, is updating rainfall distribution data to ensure current stormwater management systems can handle future weather changes.

"We are looking at how the state can minimize risk by developing a better understanding of past weather variability while looking forward at the variability expected with future climate change -- whether it is farm production systems or stormwater management," Hutchinson said.

Collaborators on the project include Shawn Hutchinson, associate professor of geography; Aavudai Anandhi Swamy, research assistant professor of agronomy; and Vahid Rahmani, doctoral student in biological and agricultural engineering, Iran. Rahmani is researching Kansas rainfall data and recently received a first-place award at the K-State Research Forum for his oral presentation "Intense rainfall events distribution pattern in the state of Kansas."

"Our research involves understanding how climate change and land cover change -- which is the conversion of natural prairie land and agricultural land to urban and suburban land uses -- affect the potential for flooding," Hutchinson said. "It's where the variability of reality meets the built engineered world."

When engineers design stormwater management systems -- such as terraces and grass waterways in or storm sewers with underground pipes that transport road runoff to the nearest body of water -- these systems are usually designed to handle a specific storm. In the Manhattan area, natural systems such as grassed waterways and terraces are designed to handle slightly more than 3.5 inches of rain in 24 hours. This rainfall event is expected to happen once every 10 years.

Issues arise because the National Weather Service has not updated rainfall distribution maps for the state of Kansas since 1961. Researchers are updating this data to provide a more accurate weather benchmark that engineers can use when designing stormwater systems. Kansas is ideal for studying climate change and variability because there is more variability across Kansas than from the eastern edge of Kansas to the Atlantic Ocean, Hutchinson said.

To track and understand how they have changed, the researchers conducted a similar analysis as the 1961 data. Rahmani studied weather and from 24 weather stations in Kansas and 15 stations outside the state. The researchers noticed several trends in the data they collected.

"We're actually seeing more rain across the state, which is kind of surprising because we thought it would be getting drier in the western part of the state," Hutchinson said. "We are getting wetter across the state, but it is much more drastic in the southeast, where we are seeing more high-intensity storms."

The research team found that the 1961 data overestimated the size of storms. That means the currently designed systems are adequate for stormwater management, Hutchinson said, but if the shift in more rain and stronger weather events continues, stormwater systems may need to be redesigned.

"There is discussion among the engineering community about if we need to rethink the size of storm that we design for," Hutchinson said. "The bottom line is that now we have an idea of how weather trends have shifted across the state. This information will be useful to anybody who deals with stormwater runoff -- from the Kansas Department of Transportation to agricultural producers."

The research also is helpful for improving natural stormwater systems, which especially interests Hutchinson. She has studied how to move away from the concrete jungle of pipes and move toward more natural stormwater management systems, such as wetlands, rain gardens and terracing. Challenges exist with natural systems because climate and land cover changes have caused many more peaks and valleys in stormwater runoff -- from times with flooding to drought periods. As a result, natural systems tend to be at capacity in the spring because of increased rainfall and they tend to dry up during the summer when it rains less.

"We needed a better understanding of the variability of the so that we could better understand any risks with these natural systems," Hutchinson said. "The amount of water that flows through a pipe is pretty consistent and you can always size a pipe. But the amount of water that can be absorbed by a wetland systems is a lot more in August when it is hot and dry than it is in May."

The researchers are continuing to analyze data and are preparing the research for publication. Their work is funded as part of the $20 million Kansas National Science Foundation Experimental Program to Stimulate Competitive Research project researching global and renewable energy research.

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