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Rock-sills are instream low-head structures generally used to stabilize the riverbed. Their presence causes the formation of pools and riffles along the river, thus improving the aquatic habitat and creating resting spots for aquatic species. In this study, the riverbed morphology due to the rock-sill configuration installed at river bends was experimentally analyzed under clear-water condition, with a uniform, granular bed material. Tests were conducted by varying the inclination of sills with respect to the radial direction in three curved bends. Experimental evidence confirmed that the curvature of the channel bend plays a fundamental role, i.e., scour features significantly differed from those occurring in straight channels. Likewise, the inclination of the sill and its shape affect the scour morphology. The presence of the sill and the curvature of the channel caused an asymmetric distribution of the flow in the radial direction, possibly resulting in a shift of the scour hole toward the center. The analysis of experimental data allowed us to provide practitioners with a useful formula to predict the maximum scour depth. Finally, interesting insights on scour dynamics and features at equilibrium are also presented. [ABSTRACT FROM AUTHOR]

A new prediction formula is proposed to determine wave-induced pore pressure height distribution inside the core of rubble-mound breakwaters. Existing observed field and experimental data in the literature have been examined, and a valuable database has been obtained. Using dimensional analysis, a new wave damping parameter has been derived. In comparison with the existing empirical Biesel's formula, the proposed prediction formula directly takes into account the influence of the mean diameter of the core material, water depth, and important wave parameters such as incident wave height and wavelength, and there is no more necessity to assume appropriate values for the seepage coefficient and the material coefficient that are essentially needed for Biesel's formula. The new prediction formula presented here has its merits in providing an alternative form and insight into the physics of phenomena. [ABSTRACT FROM AUTHOR]