INDIANAPOLIS — Anticipated increases in annual rainfall should signal a need for Indiana to consider whether existing storm water systems can handle flooding, experts told a legislature-appointed panel.
“We are seeing an increasing number of days per year that are having these extreme rainfall events,” Indiana State Climatologist Beth Hall said. “These maximize the capacity of the storm water systems, the drainage systems in the area.”
Indiana’s annual rainfall has increased by about 5 inches during the past century; southern Indiana has seen the largest jump, about 7 inches.
In late August, Hall and other experts discussed climate and water trends with the 14-member Storm Water Management Task Force, which will issue by December recommendations for storm water needs in Indiana. The panel is to discuss rural issues Sept. 18 and Oct. 1.
In 2014, the Indiana Chamber of Commerce issued a report on Indiana’s water utilities noting it would take $100 million annually to improve Indiana’s storm water infrastructure. That figure doesn’t take into account an initial investment of more than $2 billion to improve drinking water infrastructure.
In many cases, the Indiana Finance Authority issues low-interest loans to communities performing storm water projects. The IFA currently has four storm water projects yet to be funded this year for $8 million.
Among other funding sources, the Indiana Office of Community and Rural Affairs awarded $600,000, the maximum allowed, last year for storm water improvements for the town of Jamestown to install a drainage swale and inlets and reconstruct three channels.
Compounding recent concerns are reports that the Hoosier state will warm by 5-6 degrees by mid-century.
“The spring and the winter are expected to get substantially wetter,” said Jeff Dukes, director of the Purdue University Climate Change Research Center.
“We expect more precipitation in the seasons when plants are taking that water up out of the soil, when soils are already likely to be saturated and the water is not very useful to us.”
Saturated ground leads to runoff from tile drains, he said, with an increase of up to 50% in water flow in the spring. Purdue researchers are studying the impact of climate change on water flow.
“The general message here is that annual rainfall has been increasing and in recent years has been increasing at a faster rate,” Hall said.
Some states have stations monitoring soil moisture, perhaps one of the best ways to study storm water runoff. For example, Oklahoma has about 100 stations with information posted on a website.
Although Indiana has soil temperature monitors, it does not have moisture monitors throughout the state. Hall asked that the panel consider adding stations as one way to monitor possible flooding.