Reevaluation of the Gap Formation in the New Orleans Levee System

AbstractIn the aftermath of Hurricane Katrina, studies pointed out that gap formation was related to breaches of many floodwalls in New Orleans. However, it is still necessary to discern whether those gaps were the cause or the result of the failure to justify the application of retrofitting techniques designed to correct gap formation problems. For that purpose, this study conducted numerical and analytical evaluations to investigate the in-depth mechanism of gap formation using an effective stress approach. To this end, it was found that gap was the cause of failure for the London Ave. canal because of the seepage effect; however, it could be the result of failure for the 17th St. canal because of the subsidence of the soft soil layer underneath the levee. When the stiffness and strength of the soft layer were increased considering the geotechnical variability in the numerical analysis for the 17th St. canal, however, it showed that the failure mode changed and gap became the cause of failure, meaning t...