Abstract
Sand bar migration on the gently sloping sandy bottom in the coastal zone as a result of nonlinear wave transformation and corresponding sediment transport is discussed. Wave transformation on the intermediate depth causes periodic exchange of energy in space between the first and the second wave harmonics, accompanied by changes in the wave profile asymmetry. This leads to the occurrence of periodical fluctuations in the wave-induced sediment transport. It is shown that the position of the second nonlinear wave harmonic maximum determines location of the divergence point of sediment transport on the inclined bottom profile, where it changes direction from the onshore to the offshore. Such sediment transport pattern leads to formation of an underwater sand bar. A method is proposed to predict the position of the bar on an underwater slope after a storm based on calculation of the position of the maximum amplitude of the second nonlinear harmonic. The method is validated on the base of field measurements and ERA 5 reanalysis wave data.
Highlights
Sand bars as morphological forms are found almost everywhere on the gentle coastal slopes of the seas and oceans
Their formation and behavior are the result of the interaction of waves and currents, and their dynamics can largely characterize the state of the coastal zone [1,2]
Sloping sandy coasts’ morpho-dynamics are strongly affected by wave transformation processes, one of which is a nonlinear triad interaction that leads to quasiperiodic changes in space of the wave profile due to periodic exchange of energy between 1 and 2 wave harmonics
Summary
Sand bars as morphological forms are found almost everywhere on the gentle coastal slopes of the seas and oceans Their formation and behavior are the result of the interaction of waves and currents, and their dynamics can largely characterize the state of the coastal zone [1,2]. High waves break on the top of bars and cause strong offshore currents (“undertow”) that transport the sediment toward the sea, resulting in sand bar migration from the coast and beach erosion [4]. Cyclic bar movements were observed on a scale of several years or decades, which is associated with global changes in the wave climate, depending on the main teleconnection patterns [6,8], but sometimes the behavior of the sand bar at a scale of several years does not depend only on the wave action, and on tides and currents, such as the long-term migration of the bars from the coast to offshore noted in [9]. The order of several storms can have an effect on bar shape and lead to episodic bar migration [9]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call