The tsunami mitigation strategies are shifting from single to multiple defense systems in recent times. In this study, the mitigation effects of continuous and discontinuous emergent coastal forest were investigated experimentally focused mainly on energy reduction of the inundating tsunami current under subcritical flow conditions. To improve the effectiveness of the coastal forest, a layer of short submerged trees with the varying condition of porosity (P_r = 98%, 95%, 91%, and 79%) was coupled/incorporated and tested with the tall emergent trees. The results revealed that the forest in discontinuous placement effectively produced resistance to the flow by notably increasing the backwater rise in the upstream and reducing the energy of the tsunami current in the downstream region, rather than a continuous forest belt. The incorporation of short submerged tree layer within an emergent tall tree forest further increased the flow resistance by causing a large water level difference between the upstream and downstream regions of the forest, which consequently resulted in a significant amount of energy loss i.e. 30–50% higher, in comparison to that of single layered emergent tree configuration. Moreover, the critical zone of high shear stress and large turbulence hydraulic jump formation zone was observed to significantly move in the further downstream region for discontinuous and layered tree forest configurations, that could possibly save the direct collision of water with the ground just behind the forest. The outcomes predicted by the statistical analysis approach also showed a strong inverse correlation between the energy dissipation of flow and forest porosity.

近来，海啸缓解战略正在从单一防御系统转变为多重防御系统。在这项研究中，通过实验研究了连续和不连续的紧急沿海森林的减缓效果，主要集中在亚临界流动条件下淹没海啸流的能量减少。为了提高沿海森林的有效性，一层具有不同孔隙度的短沉水树（P _r = 98%、95%、91% 和 79%）与高大的新兴树耦合/合并和测试。结果表明，不连续分布的森林通过显着增加上游的回水上升和降低下游地区的海啸电流能量有效地产生了流动阻力，而不是连续的森林带。在涌现的高大乔木林中加入短的沉水树层，通过导致森林上游和下游区域之间的大水位差进一步增加流动阻力，从而导致大量的能量损失，即 30-50%与单层紧急树配置相比，更高。而且，观察到高剪切应力和大湍流水跃形成区的临界区显着移动到更下游的区域，以形成不连续和分层的树木森林配置，这可能会避免水与森林后面地面的直接碰撞。统计分析方法预测的结果还表明，流动能量耗散与森林孔隙度之间存在很强的负相关。