Nonlinear wave theory validated by field data for predicting wave-induced shear stress and turbidity under extreme events

Coastal sediment transport is a dynamic process influenced by the continuous interplay of waves and currents. However, traditional models based on linear wave theory often fail to capture the full complexity of nearshore turbulence. In this study, we present the first field-based application of nonlinear wave theories—including third-order Stokes and cnoidal wave formulations—to quantify wave-induced shear stress and evaluate its impact on turbidity. Utilizing in situ measurements from four extreme hydrodynamic events—Typhoon Dujuan (2015), Extreme Cold Surge (2016), Prolonged Heavy Rainfall (2018), and Typhoon Wipha (2019)—off the coast of Houwan, Taiwan, we reveal a compelling pattern: third-order Stokes theory not only predicts higher magnitudes of shear stress but also exhibits remarkable temporal alignment with observed turbidity surges. In contrast, current-induced shear stress remains relatively low. These findings challenge the prevalent reliance on linear wave assumptions and establish a validated nonlinear modeling framework for coastal morphodynamics. By capturing the episodic chaos associated with storm-driven seas, this study provides critical insights for predicting sediment transport in light of intensifying climatic extremes.