Mohammad Vaghefi

Analysis of bed topographic changes downstream of culverts is significant in maintaining the stability of these structures. Since bed topography changes in different conditions and at different points in time, the time-related evolution of bed topography at the down side of a culvert was investigated under various circumstances. This study included tests on a culvert placed under un-submerged (US), semi-submerged (SS) and fully-submerged (FS) conditions. The bed materials were uniform, and the flow discharge rate was constant in all tests. Based on the observations, the value of the maximum scour depth decreased with the SS and FS culverts at any point of the test time, in comparison with the non-submerged culvert. Additionally, it was found that prolonging the duration of the testing period led to a drop in the average sediment transport rate across all examined conditions. Subsequently, as the water level continued to rise and the culvert became FS, a discernible reduction in bed topography variations was noted. With the observed increase in flow velocity from 0.28 m/s in a FS condition (where the water depth was equivalent to 0.37 times the culvert opening’s width) to 0.86m/s in a US condition (where the water depth was equivalent to 0.12 times the culvert opening’s width), there was a corresponding increase in the maximum scour depth by a factor of 106%.