Elongation of a Sand Spit Offshore of Groins Due to High-Angle Wave Instability

Elongation of a sand spit offshore of groins was investigated using satellite images for the convex shoreline near Cabaruan located on the bottom of Lingayen Gulf in the Philippines. Similar to the extension of a large-size sand spit offshore of Santo Tomas, a sand spit was formed by the long shore sand transport turning around the tip of groins at Cabaruan owing to high-angle wave instability. The elongation of a sand spit was numerically predicted using the BG model (a model for predicting 3-D beach changes based on Bagnold’s concept). Predicted results were in good agreement with measured changes in sand spit.