We use high-resolution two-dimensional simulations to model the generation and evolution of nonlinear internal waves formed as a result of the interaction of a first-mode internal wave field with idealized slopes. The derivation of the energy equation and the energy flux terms are presented. By employing an analysis of the distribution of the energy flux across the shelf break, we quantify the contributions to the energy flux budget from nonhydrostatic as well as nonlinear effects in comparison to the contribution from the baroclinic pressure anomaly term used widely for linear internal waves. Our results show that the contributions to the total energy flux from these additional terms are significant in these large nonlinear internal waves, consistent with recent field observations.