Levee scour from overtopping storm waves and scour counter measures

Laboratory wavetank experiments were performed on the landside levee scour induced by floodwall overtopping. The objectives of this study were to elucidate the landside levee scour characteristics and evaluate the effectiveness of selected scour counter measures. Model levees, both with and without a scour protection measure, were constructed. Four scour protection armoring were tested: riprap, coreloc, riprap with an underlayer, and coreloc with an underlayer. The levee soil was composed of a sand-clay mixture. The geometric scour characteristics of interest driven by their practical importance were maximum scour depth and scour length. Both the maximum scour depth and the scour length exhibited an exponential trend in approaching equilibrium values, with the scour length reaching equilibrium sooner. Parameterizations for predicting the values of the maximum scour depth and length while approaching the equilibrium and at the equilibrium state were developed. Though the riprap armoring cover proved more effective than the coreloc armoring cover, the presence of an armoring underlayer was a greater impetus of the overall effectiveness of both protection measure types. Therefore, it is recommended that the placement and size distribution of the underlayer be adjusted in the field accordingly for the greatest disaster prevention and economic advantage.

► Landside levee scour due to floodwall overtopping is studied in the laboratory.
► The transient and equilibrium characteristics of levee scour are elucidated.
► Maximum scour depth and scour length parameterizations are proposed.
► The effectiveness of four different types of scour countermeasures is evaluated.
► The selection and placement of scour countermeasure armoring are discussed.