Author(s): Selim M. Sayah
Linked Author(s):
Keywords: Soft Shore Protection; Wave Field; Gap; Brushwood Fences; Physical Modeling; Wave Damping; Numerical Modeling
Abstract: A common soft protection measure, called brushwood fences, is widely used in shallow regions of large lakes in Switzerland where high waves, during major wind events, are able to reach the shore and induce severe erosion. Mainly constructed of wooden piles and tree branches, brushwood fences are often used as porous coastal protection structures. However, the scientific basis for their specific design still needs to be explored in detail. One of the major questions that remain to be answered, concerns the effect of gaps in the structure on wave field in the protected area. The analysis focuses on the modification of the wave field behind the structure for a varying width of one gap and spacing between two gaps. Based on 2D numerical modeling, the analysis uses the results of the physical tests carried out in a wave tank with downscaled brushwood fences. In a first stage, the experimental results are used to calibrate the numerical model using some major variables of wave breaking and bottom roughness. Afterwards, the transmission coefficients of the structure obtained by the physical tests are introduced in the model as friction coefficients. This calibration allows a systematic and comprehensive numerical investigation of the effect of gaps on wave transmission, diffraction, and damping behind the structure in an enclosed area. The results show that for a single gap, high waves are concentrated in the middle of the protected area which is less influenced by the gap width. However, for the configuration of two gaps, the wave field is significantly influenced by the spacing between them. A dimensionless analysis brings out adequate values for an optimal spacing.
Year: 2005