SYCAMORE – Beginning this month, the Illinois State Water Survey is conducting a study of flood risks in DeKalb County, with the hope that new research can identify how to better plan flood mitigation efforts.

Data collection, the first phase of the research project, begins this month and won’t be completed until early fall, according to a news release from an Illinois State Water Survey and Prairie Research Institute official.

Christopher Hanstad, a senior hydraulic engineer with the Illinois State Water Survey and Prairie Research Institute, said the measurements of bridges, culverts and stream channels in Sycamore, as well as local elevation data will be collected by a field survey crew. Usually, the survey crew begins by locating area benchmarks to establish a starting elevation to reference their collected data, Hanstad said. Once those control elevations are established, the crew primarily will collect the elevations of stream channels, bridges and culverts.

“Having accurate representation of the stream channels and bridges helps the Illinois State Water Survey (ISWS) engineers develop hydraulic models to simulate flood flows through the stream and floodplain. Conventional terrain datasets do not typically reflect the stream bathymetry below the water surface, therefore, the stream channel survey data helps us to model the full stream channel capacity,” Hanstad wrote in a statement.

As of July 11, the majority of Illinois was in a moderate or extreme drought, according to the National Integrated Drought Information System, but Hanstad said the lack of rainfall may actually help the water flow survey.

“Generally, low flow conditions are most ideal for the survey crew to collect elevations, particularly for the stream channels. High stream flow create inaccessible or even dangerous conditions to collect data,” Hanstad wrote.

Sycamore is the primary location of the field surveys because Blue Heron Creek and the East Branch South Branch Kishwaukee River – waterways surveyors said they want to better understand – run through the city.

“This project to perform new floodplain studies in DeKalb County is part of a much broader multi-phase project in the Kishwaukee watershed,” Hanstad wrote. “The project began in 2017 as a discovery project funded by [the Federal Emergency Management Agency] to research the watershed and engage local communities and stakeholders to discuss flood risk within the watershed. ... The current phase of the project focuses on the hydrologic and hydraulic data development to perform the new modeling and develop new floodplain delineations for the streams being studied in the watershed.”

The results of the study will be used to formally update regulatory flood insurance rate maps for DeKalb County, but that map won’t be finished until 2028, at the earliest.

“The regulatory map phase is still several years away from beginning and takes several year to complete since it involves a lot of due process,” Hanstad wrote. “So it will be at least 5 years before there are new regulatory floodplain maps in effect for Dekalb County.”