Dynamic equilibrium planform of embayed beaches: Part 2. Design procedure and engineering applications

Abstract

The design of equilibrium beach systems employing beach nourishment techniques in conjunction with coastal support structures has received increased interest from coastal engineers in recent years. One such solution to remedy coastal erosion problems is to design an equilibrium pocket beach in order to stabilize the shoreline. Such coastal landforms may exist in nature in static or dynamic equilibrium states. The concept of the Static Equilibrium Planform (SEP) has received much more attention from coastal engineers than that paid to the Dynamic Equilibrium Planform (DEP). This paper presents a design procedure for embayed beaches in dynamic equilibrium which have a specific net littoral drift rate. The proposed methodology employs the net sediment transport rate passing through the bay, together with the time series of the wave climate impinging on the beach, in order to compute the angle (γd). This angle represents the difference in degrees between the direction of the mean wave energy flux at the diffraction point (θEF) and the orientation of the dynamic equilibrium beach (θDB), to be utilized in a newly derived DEP formula to predict the shoreline shape in the long term. The procedure was applied and validated using prototype bays in dynamic equilibrium with different net sediment transport rates along the Brazilian coast, producing good results. Furthermore, it was employed as a tool to investigate the influence of changes in the net annual littoral drift rate on the (DEP) shape in a case study along the Spanish coast. Taken together, these confirm its utility as a valuable tool for coastal management and engineering practice.