A note on alongshore sediment transport on weakly curvilinear coasts and its implications

• Simple approach for alongshore sediment transport (AST) on curvilinear coasts
• Variations in wave conditions, beach geometry and sediment size are considered.
• Analytical expression of AST using a simple approximation for wave propagation
• Implications on morphodynamics: 3 movements for undulating shorelines are found.
• Consequences on shoreline modeling and nearshore hydrodynamics are discussed.

This paper presents a simple approximation for assessment of the alongshore sediment transport rate on dissipative weakly curvilinear coasts. The approximation considers spatial variations in the wave angle and energy, sediment size, beach slope and type of wave breaking inside the surf zone. Similar approaches were employed in the past for coasts forced by high oblique waves where shoreline undulations frequently develop. With our approach, we can analyze more realistic situations, i.e., alongshore relations between the sediment size and the beach slope. The general expression for alongshore sediment transport is made explicit using a simple model for wave propagation. The solution is used to examine the implications of the behavior of alongshore sediment transport on shoreline evolution. After the analysis of the effects of variations in the wave conditions, the alongshore beach slope distribution and the shoreline geometry, three different shoreline tendencies were obtained for undulating shorelines: migration for changes in deep-water wave angle; amplitude growth for increases in wave height or period and changes in shoreline geometry; and wavelength changes and asymmetries for coasts with alongshore changes in beach slope. Our results also indicate that wave setup may enhance the formation of undulating shoreline features.