Impact of combined sewer overflows on hydrodynamics and sediment transport during flow reversal events in Chicago area waterway system

Combined Sewer Overflows;Flow Reversal;Hydrodynamics;Sediment Transport;Chicago Area Waterway System

Chen, Chieh Ying ; Garcia ; Marcelo H.

关键词: Combined Sewer Overflows;    Flow Reversal;    Hydrodynamics;    Sediment Transport;    Chicago Area Waterway System;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/101138/CHEN-THESIS-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Chicago Area Waterway System (CAWS) is a complex hydraulic system in Great Chicago Area, and it is also the linkage connecting Lake Michigan to the Mississippi Watershed. As is well-known, the Chicago River Diversion changed the flow direction westward to the Illinois River to prevent the pollution of Lake Michigan: the main source of fresh water. However, the controlling works in the lake front will be opened to reverse the flow direction toward Lake Michigan to prevent downtown Chicago from flooding during extreme storm event. Consequently, the operation of gates and water level difference between lake and channel would determine the flow direction and influence navigation in the CAWS.Bubbly Creek is an old tributary of the South Branch of the Chicago River, and is one of the main sediment sources in CAWS which can result in abundant organic material and waste along benthic sediments. Depending on its magnitude, the discharge of combined sewer overflow (CSO) from the Racine Avenue Pumping Station (RAPS) can resuspend the sediment from the bed of Bubbly Creek and cause high sediment concentration in the channel during storms. In addition, the sediment transport from Bubbly Creek is sensitive to flow direction in the South Branch of the Chicago River. Therefore, sediment from Bubbly Creek could potentially flow north towards the Chicago River and cause ecological concerns and beach closings along the shoreline of Lake Michigan during flow reversal events.In this study, a three-dimensional hydrodynamics and sediment transport model based on Environmental Fluid Dynamics Code (EFDC) is applied to simulate two storm events with and without gate operation, respectively. This model is also capable of simulating discharge and gate operation at the lake front, where the Chicago River Control Structures (CRCS) are located. With the help of measured data, the hydrodynamics model was validated and can be used to analyze the impact of CSO on sediment transport with different flow directions in CAWS.