Enterprise Staff
Residents have until the end of the month to submit comments on a feasibility study on flooding risks and mitigation plans along the DuPage River.
The Feasibility Report and Integrated Environmental Assessment (EA) was released in late July, with results of the DuPage River Study conducted by the United States Army Corps of Engineers (USACE).
The study is designed to investigate overbank and backwater flooding along the DuPage River and its major tributaries. In doing so, it identifies and prioritizes high-risk areas, and helps to develop a range of possible structural and nonstructural alternatives to address flood risks.
The study area has experienced rapid development over the past several decades and currently includes 40 communities and approximately 900,000 residents.
The total watershed area is 378 square miles, with the mainstem watershed running 169 square miles, the West Branch DuPage River watershed covering 128 square miles, and the East Branch DuPage River watershed stretching 81 square miles.
Major storm events caused flooding along the DuPage river in 1996, 2008, 2010, and 2013.
An assessment of existing and projected future conditions determined that a significant risk of overbank flooding exists across most of the watershed. Expected annualized flood damages are estimated at $5.1 million over the 50-year period of analysis for the study.
The need to manage flood risk within the watershed was highlighted by major flooding that occurred in the spring of 2013. On April 18, 2013, a large portion of northeastern Illinois received an average of five inches of rainfall, with localized precipitation of over seven inches over an 18- to 24-hour period.
The study area received widespread rainfall between 0.25 and 1.5 inches several days before the event, which saturated the ground and increased the potential for overbank flooding when heavier rains fell a few days later. The result was significant flooding throughout northern Illinois.
DuPage and Will Counties were included in the Federal Disaster Declaration associated with the event and received a combined total of more than $22 million in FEMA and other public support funds.
The feasibility study evaluated a range of measures to address overbank and backwater flooding along the DuPage River and its major tributaries.
Structural measures such as levees or floodwalls, floodwater storage reservoirs, channel improvements, and diversions were evaluated. In addition to consideration of construction of new structural measures, the optimization or rehabilitation or existing structures was also evaluated.
Physical nonstructural measures such as acquisitioning, floodproofing, and elevation of structures were evaluated individually to determine whether they were economically justified.
The study provides recommendations for flood risk reduction through acquisition, elevation, or floodproofing structures. Nonstructural features are included within the communities of Plainfield, Minooka, Shorewood, Joliet, Bolingbrook, Naperville, Warrenville, Lisle, and Glen Ellyn as well as within unincorporated DuPage and Will Counties. The nonstructural plans include modifications of 42 structures including likely acquisition of 4 structures, elevation of 23 structures, and floodproofing of 15 structures.
The Corps of Engineers is accepting public comments on the study. Comments may be submitted via e-mail or mailed to: U.S. Army Corps of Engineers, Chicago District, 231 S. LaSalle Street, Ste. 1500, Chicago, IL 60604, ATTN: DuPage River.
Comments will be accepted through Aug. 30.
The study is a partnership of DuPage County, Will County, and the Illinois Stormwater Management Planning Committee in coordination with the Illinois Department of Natural Resources.
The complete study can be found online at www.lrc.usace.army.mil/Missions/Civil-Works-Projects/DuPage-River/