Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/47930
Title: Environmental Assessment : Continuing Authority Program, Section 14, Emergency Streambank Protection, Louisiana Highway 77 at Bayou Plaquemine, Iberville Parish, Louisiana : EA #587
Authors: United States. Army. Corps of Engineers. Mississippi Valley Division
Keywords: Environmental management
Environmental protection
Erosion
Iberville Parish (La.)
Publisher: United States. Army. Corps of Engineers. New Orleans District.
Abstract: The Bayou Plaquemine banks are eroding causing steep banks resulting in undermining of the shoulders of LA Highway 77 and threatening the integrity of the highway. LA Highway 77 is an important thruway as it is used by approximately 1,610 vehicles daily, as of 2018 and serves as a collector road to access the evacuation route LA Highway 1. Bank erosion is occurring along a portion of the federally authorized navigation channel known as Bayou Plaquemine and this erosion is threatening the structural integrity of a section of Louisiana Highway 77 which runs parallel to the Bayou. The Highway is used by motorists traveling between Iberville Parish and the cities of Baton Rouge and Plaquemine, LA. The Highway is the most direct route between the city of Plaquemine and the villages of Rosedale and Grosse Tete, LA and is also the primary route from the city of Plaquemine to agricultural areas along the Gulf Intracoastal Waterway (GIWW) Port Allen to Morgan City Alternate Route. The Non-Federal Sponsor (NFS), Louisiana Department of Transportation and Development (LaDOTD), has attempted to protect and repair the Highway, but the repairs have been temporary and have only lasted approximately 4 years. This watershed is a complex hydraulic system. Various data sets such as, existing gage data, permits, surveys, Atchafalaya River basin models, and effective floodplain maps were examined to determine if fluctuations in water surface elevations along Bayou Plaquemine caused the bank failure. Based on the Hydrologic and Hydraulic assessment, Appendix C, it was determined that stream flow fluctuations in Bayou Plaquemine are caused by rainfall and that these fluctuations are the cause of the channel erosion. The Feasibility Report for Louisiana Highway 77 at Bayou Plaquemine, Iberville Parish, Louisiana, Engineering Appendix – Appendix C provides more detail on how H&H reviewed existing gage data in the basin to determine if a correlation between stages at the lock and stages in the Bayou existed. The Bayou Sorrel lock gates (south of the problem area) are closed the majority of the time acting as a dam and are only opened after a tropical storm or hurricane to drain the interior area or to control the flood pool under certain conditions. It does not appear that Bayou Sorrel or Port Allen lock operations are impacting the bank line erosion along Bayou Plaquemine.
Description: Environmental Assessment and Finding of No Significant Impact
Rights: Approved for Public Release; Distribution is Unlimited
URI: https://hdl.handle.net/11681/47930
Appears in Collections:Environmental Documents

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