2.2.2. Supercritical Flows

To the best of our knowledge, no velocity measurements have been carried out in the scour hole of a foundation in a supercritical flow. The only available information are flow depths measured under laboratory conditions by [27]. These measurements were obtained using a clear-water turbulent inflow with mobile bed conditions and *D*/*h* ≈ 10. In the presence of a scour hole, a detached hydraulic jump wrapping around the abutment was observed, as in the plane bed case, but with the detached hydraulic jump closer to the obstacle. Additionally, two parallel bow waves smaller elevations were also visible downstream from the obstacle (Figure 3).

**Figure 3.** 2D field of water level around a scoured rectangular abutment in a clear-water supercritical flow by [27]. (**a**) Photograph at initial stage of scour, and (**b**) measured flow depth field at the quasi equilibrium stage of scour.
