Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and land-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. High performance turf reinforcement mat (HPTRM) is one of the most advanced flexible armoring technologies available today for severe erosion challenges. The HPTRM uses a unique 3D matrix of nylon filaments with high tenacity polyester geogrid reinforcement at low strains to lock soil in place, and provides permanent reinforcement to prevent soil loss during storm events. A full-scale laboratory study on combined wave and surge overtopping of a levee strengthened with HPTRM was conducted in a two-dimensional laboratory wave/flow flume. This paper describes the analysis of shear stress and erosion measurement. The shear stress and average overtopping velocity on landward-side slope and levee crest are calculated; the influences of hydraulic parameters on shear stress are discussed, and the characteristics of soil loss on HPTRM-strengthened levee are given. The results indicate that after the "upper limit" of erosion is reached, the relationship between erosion rate and average velocity is approximately linear.
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