This case study originally appeared in SWS September 2021 issue as "Erosion Solution Protects New Orleans' Canal Slopes"
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New Orleans’ three outfall canals — 17th Street Canal, London Avenue Canal and Orleans Canal—are critical for providing discharge of surface water collected from the city’s storm water runoff systems to prevent flooding. The 17th Street Canal is the largest of the three canals and is the most important drainage canal in the city of New Orleans.
Erosion of the 17th Street Canal’s flood protection system was a major concern for the Southwest Louisiana Flood Protection Authority-East. The authority required a solution to protect the canal’s slope against erosive forces and prevent a floodwall breach in the event of a tropical storm event.
Solution to Slope Erosion Challenges
To mitigate channel slope erosion, engineers at Eaves-Graves Engineers Inc. chose the Geoweb 3D Confinement System to stabilize the slopes along the Metairie side of the drainage channel. By confining the in-fill material, the Geoweb system prevents flow from causing scour and erosion on slope surfaces.
Cycle Construction Co. installed approximately 380,000 square feet of GW40V6 (6-inch deep panels) over a woven geotextile along the canal’s slope and in-filled the cells with crushed aggregate. As part of the complete Geoweb system, the Geoweb panels were secured with ATRA key connective devices and ATRA tendon clips.
Benefits of GEOWEB-Confined Aggregate Channel Slopes
The Geoweb system’s 3D cellular structure significantly improves the stability and erosion resistance of granular materials compared to when left unconfined. The system can accommodate a wide range of slope angles by selecting the appropriate cell size and cell depth for the considered aggregate.
The Geoweb System:
- Uses smaller, less expensive rock — even waste rock, which decreases installation and transportation costs;
- Creates a permeable cover when drainage is desired but vegetation cannot be established; and
- Resists high velocities and tractive forces.