9:30 AM - 9:45 AM
[ACG43-03] Hydraulic experiment on the effect of vegetation on sediment transport using a rhizome model of vegetation
Keywords:Vegetation model, Hydraulic experiments, Sediment transport, Rhizome
It is well known that vegetation cover on coastal dune surfaces is effective in preventing blowing sand. However, coastal areas are affected not only by strong winds but also by tsunamis and storm surges caused by typhoons, which have been increasing in recent years. In addition, there is a concern that localized guerrilla downpours may accelerate sediment runoff from the beach due to erosion caused by the flow down the dune surface. We have studied the effect of dune surface coverage by vegetation foliage on sediment trapping by waves. However, we found that the leafy parts of the vegetation change markedly with the seasons, and that not only the surface leaves but also the rhizomes may have a significant effect on the erosion and sediment discharge.
Therefore, in this study, hydraulic experiments using models were conducted to clarify the effect of sediment trapping by rhizomes during the erosion (scouring) process, focusing on the amount of rhizomes in the soil. Three models were made: two using bamboo sticks (Model I and Model II) and one using polypropylene (Model III). Model I is an upright model that is perpendicular to the ground surface, and Model II is a model that radiates upward from the ground surface into the ground. Model III is based on the shape of the rhizome of a grass plant distributed along the coast. These models were buried in a sandy section in a two-dimensional wave generator tank, and three waves were generated in succession to simulate a storm surge and the leading edge of a tsunami. The amount of sediment transport and the maximum scour depth were measured for each wave.
The results showed that sediment transport was affected by the density and distribution of rhizomes in the soil. The sediment trapping effect of rhizomes changed during the process of rhizome exposure due to the influence of multiple waves under certain conditions.
Therefore, in this study, hydraulic experiments using models were conducted to clarify the effect of sediment trapping by rhizomes during the erosion (scouring) process, focusing on the amount of rhizomes in the soil. Three models were made: two using bamboo sticks (Model I and Model II) and one using polypropylene (Model III). Model I is an upright model that is perpendicular to the ground surface, and Model II is a model that radiates upward from the ground surface into the ground. Model III is based on the shape of the rhizome of a grass plant distributed along the coast. These models were buried in a sandy section in a two-dimensional wave generator tank, and three waves were generated in succession to simulate a storm surge and the leading edge of a tsunami. The amount of sediment transport and the maximum scour depth were measured for each wave.
The results showed that sediment transport was affected by the density and distribution of rhizomes in the soil. The sediment trapping effect of rhizomes changed during the process of rhizome exposure due to the influence of multiple waves under certain conditions.