CHAMPAIGN, Ill., 11/13/19: Scientists studying and mapping flood hazards have long identified whole neighborhoods that are vulnerable to flooding, but with new data, researchers at the Illinois State Water Survey (ISWS) can specify flood risk for individual homes and businesses.

Using field survey data, ISWS scientist Lisa Graff and colleagues conducted risk assessments that show which structures may flood, the depth of flooding likely for each property, and the expected losses for 120 properties in the city of Ottawa, over 1,500 homes in Peoria County, and 3,000 in Rock Island County.

“This information can be used to help communities prioritize projects and resources, prepare for floods, and mitigate losses. It can also show homeowners the value of flood insurance,” said Graff.

Lessening the flood risk in communities is part of the researchers’ aims to prepare and update countywide natural hazard mitigation plans. Completed assessments show the chances of a structure flooding over a 30-year period. Buildings in the 0.2% annual chance floodplain were included in surveys and assessments. A flood of that size has a 1 in 500 chance of happening in a given year.

Communities with chronic flooding problems are a high priority, as are schools, hospitals, and other critical facilities.

The final product is a comprehensive online database with structure-based information. The password-protected data are available to floodplain managers, who can in turn help to interpret the information for the public.

Other users will be community planners, zoning committees, and county boards that can conduct a benefit-cost ratio to determine which buildings are most valuable in terms of flood losses.

“Structures that are expected to have minor flooding can be elevated,” Graff said. “For structures that flood repeatedly, buying out the properties may be more cost-effective for communities considering a mitigation plan.”

The researchers’ goal is to complete a structure-by-structure assessment statewide so that planners for multiple counties or communities could collaborate on plans for natural hazards. However, funding is needed to complete the work.

Graff and ISWS engineer Sally McConkey and GIS specialist Brad McVay developed a report titled “Structure-Specific Flood Risk Assessment Studies” detailing the projects, which were funded by the Illinois Department of Community and Economic Opportunity.

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Media contact: Lisa Graff, 217-265-9430, lgraff@illinois.edu
Tricia Barker, Associate Director for Strategic Communications, 217-300-2327, tlbarker@illinois.edu