Experimental investigation of tidal bore-like unsteady flow interaction with solitary spur dike

In a river and estuarine region dominated by strong tidal bores, spur dikes play a crucial role in influencing both hydrodynamics and morphodynamics. The present study experimentally quantifies the hydrodynamics around a solitary spur dike during tidal bore-like unsteady flow interaction by varying the flow Froude number (Fr) and relative dike height ( h d /h ). During the tidal bore interaction with the spur dike, splashing occurred during bore impact, followed by continuous overflow, resulting in a significant difference in flow characteristics in the spur dike vicinity during the quasi-steady flow phase. Fr and h d /h positively correlated with the upstream water elevation (backwater rise) and negatively correlated at the downstream region. At the head region, the backwater upstream and the overtopped flow together dictated the flow characteristics. Empirical equations for predicting the flow characteristics (bore depth and velocity) around the spur dike during tidal bore interaction are obtained through the non-linear multivariate regression analysis. At high Fr and high h d /h conditions, the spur dike was found to effectively reduce the tidal bore energy at the downstream region by nearly 25% due to high turbulence intensity. Overall, the paper provides quantitative and qualitative discussion on tidal bore hydrodynamics and the variation in the tidal bore energy around a solitary spur dike for engineering design and operational appraisal. • Hydrodynamics and energy dissipation in the vicinity of a spur dike during the tidal bore interaction are investigated. • The flow Froude number (Fr) and the relative dike height ( h d /h ) define bore characteristics around the spur dike. • Empirical equations for calculating the local flow characteristics during the tidal bore interaction with the spur dike are proposed. • The tidal bore energy reduction of upto 25% at the spur dike downstream was observed.