Abstract We examined the effect of the coastal forest on tsunami sediment movement on the Sendai Plain, Japan, during the 2011 Tohoku tsunami using a numerical simulation of sediment transport. To account for the variable roughness coefficient in the coastal forest, a composite equivalent roughness coefficient was adopted. The simulated mean concentration of suspended sediment, wave height, flow velocity, and inundation limit were significantly reduced by the coastal forest. For fine to medium sand, the volumes of maximum deposition and erosion were reduced to 57–83% of those in the simulation without the coastal forest; these reductions were particularly notable for fine sand. The maximum extent and thickness of the sand layer were also reduced. The simulated sediment thickness and extent with the coastal forest for finer grain sizes roughly agreed with the observations, while the simulated results for coarser sand underestimated the observations. The reduction of sediment transport due to the coastal forest suggests that land use conditions and the vegetation environment at the time of a tsunami should be considered when studying historical and paleo-tsunamis using the geological evidence.

中文翻译：

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沿海森林对海啸沉积物输送的减少作用：日本仙台平原 2011 年东北海啸的数值模拟

摘要 我们在 2011 年东北海啸期间使用沉积物传输的数值模拟研究了沿海森林对日本仙台平原海啸沉积物运动的影响。为了解释沿海森林中的可变粗糙度系数，采用复合等效粗糙度系数。沿海森林显着降低了模拟的悬浮泥沙平均浓度、波高、流速和淹没极限。对于细沙和中沙，最大沉积和侵蚀量减少到没有沿海森林的模拟中的 57-83%；这些减少对于细砂尤为显着。砂层的最大范围和厚度也减少了。沿海森林对细粒度的模拟沉积物厚度和范围与观察结果大致相符，而粗沙的模拟结果低估了观察结果。沿海森林造成的泥沙输运减少表明，在利用地质证据研究历史和古海啸时，应考虑海啸发生时的土地利用条件和植被环境。