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Title:Hydraulic modeling and performance evaluation of low water crossings in Illinois
Author(s):Gautam, Sudip
Advisor(s):Bhattarai, Rabin
Department / Program:Engineering Administration
Discipline:Agricultural & Biological Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Low water crossings
Hydrologic engineering center’s river analysis system (HEC-RAS)
Abstract:The Illinois Department of Transportation (IDOT) and local agencies monitor and regulate the 146,764 miles of roadway that are open to public travel in the State of Illinois. There are many old and aging bridges, culverts, and low water crossings on rural low-volume roads that need to be replaced. Low water crossings (LWCs) have been used as an economical alternative to culverts and bridges, designed without overtopping, on low-volume roads where there is a low number of floods. The lack of design guidance has posed difficulty for county engineers in Illinois in deciding when, where, and which type of low water crossing to use. The resulting structure is often either overdesigned or underdesigned. A study was conducted to design the guidelines for LWCs in Illinois at the University of Illinois at Urbana-Champaign in collaboration with the U.S. Army Corps of Engineers - Construction Engineering Research Laboratory (CERL) and support from the IDOT. The study included literature review, a LWC survey, and case studies on LWCs in Illinois. The results of a survey conducted among the county engineers in Illinois about their experience with LWCs are presented, and commonly used LWCs are also discussed. In this study, five existing LWCs in Illinois are selected, modeled in HEC-RAS to analyze their performance. The ability of the LWC to pass the design flow, the effect of the LWC on the floodplain of the stream, sediment transport, and movement of fishes across the LWC have been taken into consideration in the performance evaluation. From the case studies, it was found that most of the modeled LWCs were able to pass the design flow, but are not conductive to the sediment transport and aquatic organism movement. Results from the flood inundation studies show that the change in the inundated area compared to the baseline scenario is within 5% in most of the cases. There is a significant decrease in the shear stress and velocity in the cross section upstream of the crossing, restricting the sediment transport. LWCs are acting as a sediment trap, which over the long period of time will modify the channel characteristics and affect the stream dynamics. LWCs provide a restriction to the flow of water and increase inundation under higher flows but allow smooth and safe movement of vehicles across the streams. There are over 26,000 road-stream crossings in Illinois, and implementation of proper LWC design guidelines could save local agencies significant funding and provide better adaptability and storm-proofing characteristics, as well as reduce impacts to aquatic organism passage.
Issue Date:2016-12-07
Rights Information:Copyright 2016 Sudip Gautam
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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