10:15 AM - 10:30 AM
[ACG48-05] A Hydraulic Study of the Effect of Tree Rhizome Depth on Overturning Resistance of Trees
Keywords:Tree rhizome model, Hydraulic experiments, Sediment transport
The 2004 Sumatra earthquake and the 2011 Tohoku earthquake caused extensive damage to coastal areas, and coastal vegetation such as coastal disaster prevention forests was reported to reduce the damage. On the other hand, it was confirmed that trees with short hanging roots (so-called roots extending deep into the soil) were converted into driftwood due to scouring of soil, which is the base of standing trees. Restoration forests are planted on top of the base fill in order to develop deep underground roots to improve the effectiveness of disaster prevention. However, it has not been clarified to what extent the drooping roots exhibit resistance to overturning against waves in relation to the diameter at breast height and tree height, and to what extent the amount of horizontal roots (so-called roots extending near the ground surface or into the soil) affects the overturning resistance in relation to the amount of drooping roots. The amount of sediment scouring around a tree stand is also affected by the complex shape of the rhizomes due to flow. The relationship between the loss of bearing capacity due to sediment runoff and overtopping resistance due to rhizome shape is unknown.
In this study, hydraulic experiments were conducted using a model. Experiments were conducted to verify the overtopping resistance of tree trunks, rhizomes (rhizome volume and shape), soil distribution volume, and scouring volume against the flow. The model was made at a scale of 1/10, placed in a horizontal sand bed in a channel, and subjected to two types of steady flow with different wave heights. Models were examined in terms of the depth of the rhizome inserted into the sand bed (five types) and the breast height diameter of the models (three types). The time to overthrow increased with the depth of the rhizome. However, when the breast height diameter of the models was compared, a different trend was observed depending on the wave height, indicating an increase in the amount of scour at the time of overthrow.
In this study, hydraulic experiments were conducted using a model. Experiments were conducted to verify the overtopping resistance of tree trunks, rhizomes (rhizome volume and shape), soil distribution volume, and scouring volume against the flow. The model was made at a scale of 1/10, placed in a horizontal sand bed in a channel, and subjected to two types of steady flow with different wave heights. Models were examined in terms of the depth of the rhizome inserted into the sand bed (five types) and the breast height diameter of the models (three types). The time to overthrow increased with the depth of the rhizome. However, when the breast height diameter of the models was compared, a different trend was observed depending on the wave height, indicating an increase in the amount of scour at the time of overthrow.