Bank Erosion Survey of the Illinois River, Volume 1.

Bhowmik, Nani G.; Soong, David

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https://hdl.handle.net/2142/94172 Copy

Description

Title

Bank Erosion Survey of the Illinois River, Volume 1.

Author(s)

• Bhowmik, Nani G.
• Soong, David

Contributor(s)

Illinois State Water Survey

Issue Date

2000-12

Keyword(s)

Erosion

Geographic Coverage

Illinois

Abstract

This report summarizes the research and surveying that were conducted in 1995 to determine the amount and severity of bank erosion that existed on the entire length of the Illinois River. The study reach extended from Grafton, River Mile (RM) 0 to Joliet, RM 286. A multi-disciplinary team of scientists traveled the entire length of the river, mapped bank conditions and erosion sites, and selected 29 reaches for detailed data collection and two sites as observation sites. Bank erosion types were developed by studying and analyzing the erosion features. The team also used fluvial and bank failure processes to guide detailed data collection at the 29 sites.

Color-coded bank feature maps were developed for the entire 286 miles of the river. These maps depict both sides of the river. Field data sheets were used at the 29 sites to record features such as bank conditions, severity of erosion, land use on the bank, and vegetation cover, surrounding features that could relate to the bank erosion. Data collection included a minimum of three bank profiles where slopes were measured, two to six bank material samples, one core sample, and at least one river cross section. All bank profiles were subsequently correlated with stage frequencies at those selected sites. Causative factors for possible bank erosion at the site were also identified by the multi-disciplinary team. All the collected data and the available flow-related data were subsequently used to classify bank erosion processes on the Illinois River.

Analysis of the data indicated:

• The median particle size diameter d₅₀ of the bank materials varied from 0.002 millimeters (mm) to 0.7 mm.
• Erosion at many bank sections occurred within the normal range of stage fluctuations (between normal pool stages and ordinary high water).
• Twenty-seven percent of the bank sections showed erosion features at elevations above ordinary high water.
• Sixty-three percent of the sections had erosion at stages within normal range of stage fluctuations. Waves and currents have significant effects during these stages.
• Seventy-four percent of the bank sections had evidence of seepage; 26 percent had piping holes or springs.
• Twenty-eight percent of the bank sections had small scarps or benches that could have been formed by waves, seepage, or combinations of the two.
• Twenty-four percent of the bank sections showed traffic-induced disturbances.
• Ten percent of the bank sections showed eddy included erosion, and 11 percent had evidence of surface drainage.
• All measured bank profiles were divided into six categories that qualitatively identified the severity of bank erosion.
• Field mapping of the bank erosion indicated that about 117 riverbank miles are severely eroded, corresponding to approximately 20 percent of the total bank length (both banks). There are also about 90 miles of riverbank that have visible erosion features but are not considered severely eroded. On the other hand, about 189 bank miles are stable, and 88 miles are either rock or protected by riprap or other structures. Several other types of bank descriptions were also used in the mapping.
• Riverbank erosion is caused by a variety of factors. The report contains the best expert opinions on the causes of erosion at each site as was identified by the team making the field trips.

This is the first time a field study on the detailed bank erosion features of the Illinois River has been completed. The study included development of maps, collection of field data, and correlation of the approximate causative factors for bank erosion. Future site-specific or systemwide investigations will certainly benefit from this investigation.

Publisher

Illinois State Water Survey

Series/Report Name or Number

ISWS Contract Report CR-2000-11

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/94172

Has Version(s)

https://catalog.hathitrust.org/Record/102297500

Copyright and License Information

Copyright 2000 Board of Trustees University of Illinois.

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