Characteristics of bulk wave run-up on shoreface-nourished beach

Abstract

This study investigates wave run-up behaviour on nourished beaches with an artificial sandbar through a combination of physical experiments and phase-resolving numerical model SWASH. The research focuses on the dynamic interactions between wave run-up and morphological changes of the nourished beach. Results show that the presence of an artificial sandbar does not always reduce wave run-up. Under specific storm wave conditions, run-up energy on the nourished beach can exceed that on the natural (undisturbed) beach, particularly in low- and mid-frequency bands. This is attributed to wave energy shifting toward lower frequencies and resonances between the artificial sandbar and shoreline, as confirmed by first-order resonant frequency estimations. Temporal analysis of frequency components reveals that variations in crest water depth and seaward slope of the artificial sandbar significantly modulate total, low-, and high-frequency run-up, although high-frequency swash remains dominant throughout the morphological evolution. Existing empirical parameterizations for wave run-up, primarily developed for natural beaches, were evaluated against model results. While reasonable agreements are achieved, they tend to overlook the effects of submerged features and the saturation behaviour of run-up under specific conditions. The run-up prediction accuracy is improved by incorporating the dimensionless crest water depth in the modified formula, demonstrating its potential use for fast predictions of wave run-up on evolving nourished beaches.