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Recent heavy rainfalls in Northeast Illinois not only caused damaging floods, but also polluted waterways such as the Des Plaines River because of the loss of wetlands and their capacity to store flood waters and remove contaminants.
"Flooding, in urban areas where wetlands have been destroyed, is most often associated with water quality problems,” said Donald Hey, director of Wetlands Research, Inc. (WRI). “Wetlands can capture and remove pollutants that are washed away during intense rainfall events such as those we have experienced recently. Everything from lawns to oil slicked roadways and parking lots contribute polluted water, known as non-point pollution, to our rivers and lakes. Wetlands safely store flood waters, help remove pollutants and, in the long-run, provide other important benefits, such as wildlife habitats."
WRI manages restored wetlands along the Des Plaines River near Wadsworth, Ill., and is working on restoring a wetland known as Neal Marsh near the intersection of highway 41 and Stearns School Road in Lake County.
Wetlands store excess rainfall and reduce the extent of floods and the damage they can cause. Without the wetlands, flood damage would have been even more severe in areas south of the project. As flood waters recede, these restored wetlands will help clean the water by removing sediment, nitrogen and other pollutants. WRI is conducting research to determine specifically how wetlands improve water quality during heavy rains.
"We know that wetlands can help reduce the pollution that occurs when water runs off during heavy rains. Urban and suburban areas are particularly at risk during these incidents of nature," said Illinois Environmental Protection Agency director, Doug Scott. "After consecutive hard rains, the water can no longer be absorbed. Wetlands are especially important in regions where roads and other factors of urban development cover an increasing portion of the landscape and prevent it from naturally absorbing and infiltrating storm waters."
In Illinois, the loss of more than 90% of the state's presettlement wetlands has contributed to difficulties with flood management. While Lake County has preserved about 10 percent of its presettlement wetlands -- a rate higher than most other Illinois counties -- its remaining wetlands are threatened by development. In developed regions, runoff issues are compounded by the generally high levels of non-point source pollution materials (pollution that cannot be traced back to a single origin or source) that water gathers by washing over chemically treated lawns and farm fields as well as paved areas and other developed sites. Non-point source pollution accounts for 65 percent of the total pollution found in U.S. inland surface water, according to Scott, and most
people do not realize the damage that it poses to common waterways.
"Problems created by flooding can be magnified when there are not enough natural wetlands to help store the excess water. We are fortunate to have a number of wetlands in Lake County that help during powerful storms like we have experienced in the last week," said Jim Hayner, village administrator for Gurnee. "Property damage would have been much worse without them."
WRI is involved in an extensive public education program helping people understand the role wetlands play in reducing pollutants and improving water quality and the importance of wetlands restoration. Funding for the educational and informational outreach efforts are provided in part through Section 319 of the Clean Water Act distributed through the Illinois Environmental Protection Agency.