Effect of river vegetation with timber piling on ship wave attenuation: Investigation by field survey and numerical modeling

The objective of this study is to investigate the effects of river vegetation and timber piling on the attenuation of ship-generated waves that cause erosion at river bank. A numerical model based on two-dimensional Boussinesq-type equations was developed to predict the ship wave prorogation through river vegetation and timber piling. The model was validated with the field data and found that the model can reproduce well the field data when the disturbances from tides and winds were minimal. The numerical model was then used to simulate ship wave propagation through a belt of river vegetation consist of Rhizophora apiculata, a dominant type of mangrove planted in the Ca Mau River in the south Vietnam, and a timber piling. A 200 m long timber piling, parallel to the river bank, at 10 m from the bank reduced 51% and 89% of run-up height and wave force at the bank, respectively. If the timber piling combined with 20 m width of the vegetation the run-up height and wave force were reduced further 61% and 95%, respectively.