Developing empirical formulas for assessing the hydrodynamic behaviour of serrated and slotted seawalls

This paper presents an experimental study on the hydrodynamic performance of seawalls in terms of wave reflection coefficient (Kr), relative wave run-up (Rup/Hi), and relative wave run-down (Rdown/Hi). Various experiments were carried out under monochromatic waves to test five non-traditional seawall setups; plane wall (PW), rectangular serrated wall (RSW), triangular serrated wall (TSW), slotted wall (SLW), and triangular serrated-slotted wall (TSLW). A thin-parallel solid wall with a water chamber width (D) was used on the leeward side of SLW and TSLW in order to preclude the wave transmission. RSW was found hydrodynamically superior as compared with TSW. The blocks spacing of RSW and TSW were hydrodynamically optimized at a value of 2.5 times the width of the block. Nevertheless, the hydrodynamic behaviour of both SLW and TSLW was optimal when the slots ratio was about 0.33, whilst the chamber width was about 0.25 of the incident wavelength. New empirical formulas were developed for understanding the hydrodynamic behaviour of the proposed seawalls using nonlinear regression analysis. These formulas were calibrated using SPSS based on the experimental results. The formulas were used to predict the hydrodynamic behaviour of both RSW and TSLW for El-Tinah Plain Bay in the North-East coast of Egypt.