“…In most cases of practical relevance for environmental and geo-physical applications, the ML develops over very large streamwise distances compared to the average flow depth, such that the ML width, δ, becomes much larger than the flow depth, H. Once this happens, bottom friction has an important effect on the dynamics of the quasi two-dimensional (2-D) coherent structures inside the ML. These eddies start as billows generated via the Kelvin-Helmholtz (KH) instability by the mean horizontal shear between the two streams (Corcos & Sherman 1984;Lesieur et al 1988;Liu, Lam & Ghidaoui 2010;Lam, Ghidaoui & Kolyshkin 2016). The growth in the size of these quasi 2-D eddies and their subsequent loss of coherence strongly influences the spatial development and structure of the ML at large distances from its origin.…”