Pile Fence to Reduce Wave Overtopping and Overwash of Dune

Abstract

An experiment was performed to examine the utility of a pile fence in reducing dune erosion and overwash during a storm. Six tests consisting of 58 runs of 400 s each were conducted to compare the effectiveness of six different pile fences arranged in a single row and staggered double rows. The preliminary experiment suggests that the pile fence with a porosity of about 0.5 should be placed near the toe of the dune foreslope with a sufficient burial depth to avoid toppling. A cross-shore numerical model is adjusted to simulate the drag force acting on the pile fence. The adjusted model is compared with the beach and dune profile evolution and the wave overtopping and sand overwash rates measured in the six tests. The model is expanded to predict the extreme (5, 1, and 0.013% exceedance probabilities) of the free-surface elevation and onshore velocity for the future design of the pile fence against the wave forces. The proposed pile fence appears promising but will need to be tested at a field site.