Tsunamis - Extreme Events: A Physical Reconstruction and Risk Assessment - page 117

Figure 5.4. Narrow scour pits developed behind trees, Sissano Lagoon. Waves
travelled from right to left and where the water flow separated from the ground
surface at the back of the barrier, roller-like vortices likely developed to form the
longshore scarping (as seen in the background) and scour pits on the lee side of
trees.
Figure 5.5. Abroad scour pit developed in the absence of trees at the base of a
long-shore scarping back barrier, Sissano Lagoon.