Morphological evolution and functional adaptation of a Submerged Sand Engine subjected to recurrent storms

The Submerged Sand Engine serves multiple structural functions for coastal protection in China, but its resilience under recurrent storms remains unclear. A multi-fraction sediment transport model is developed to investigate its morphological evolution and functional adaptation at the Golden Coast. Under a typical storm, the Submerged Sand Engine induces early wave breaking by regulating nearshore water depth and causes the maximum wave attenuation rate η max of 56%. Meanwhile, the groins are particularly active in local flow reduction and alongshore sediment transport. Under a storm cluster with 15 repetitive storms, the system exhibits rapid morphological adjustment and functional degradation during the early stage of the storm cluster followed by gradual stabilization, indicating a negative feedback mechanism where storm-driven crest erosion weakens subsequent wave-breaking intensity and bed shear stress, thereby decelerating further erosion toward a quasi-equilibrium. Two logarithmic relationships are established, where one is between the normalized cumulative erosion depth ζ and the cumulative storm energy E , and the other is between η max and E . These findings highlight the self-adaptive process of the Submerged Sand Engine that maintains the residual wave-attenuation function of 43% despite substantial morphological evolution, providing predictive tools for engineering management without reliance on in-situ data during storm clusters.