Observations and numerical simulations of the braking effect of forests on large-scale avalanches
Observations and numerical simulations of the braking effect of forests on large-scale avalanches
复制标题
森林对大规模雪崩制动作用的观测与数值模拟
DOI：
10.1017/aog.2018.22
复制
发表时间：
2019
影响因子：
2.9
通讯作者：
PATRA Abani
中科院分区：
文献类型：
--
作者：
TAKEUCHI Yukari;NISHIMURA Koichi;PATRA Abani
虽然森林制动的减灾效果早已凭经验为人所知，但直到最近才被详细了解。在本研究中，我们使用雪崩动力学程序 TITAN2D 来模拟大规模雪崩，通过数值模拟确定了森林制动效果。其中一场雪崩发生在妙高市幕之泽山谷，毁坏了一片雪松林；其他事件发生在岩手山，破坏了亚高山森林。所有雪崩都损坏了许多树木并终止于森林内。在我们的模拟中，森林对雪崩的抵抗力是使用较大的床摩擦角来模拟的。通过反复试验拟合幕之泽雪崩的观测结果，得出非森林地区的河床摩擦角为 13-14°，森林地区为 25°。我们使用与幕之泽山谷雪崩相同的方法对岩手山雪崩进行了模拟，并获得了观测与模拟之间的良好一致性。模拟显示，如果没有森林，雪崩将比幕之泽山谷的森林实际末端移动至少 200 m，而在岩手山则至少移动 200 m，甚至可能最多 600 m。因此，这项研究清楚地表明森林对雪崩具有制动作用。
Although the disaster reduction effects of forest braking have long been known empirically, they have not been known in detail down to recent. In this study, we ascertained forest braking effect by numerical simulations using the avalanche dynamics program, TITAN2D, to model large-scale avalanches. One of these avalanches occurred in the Makunosawa valley, Myoko, and damaged a cedar forest; the others occurred on Mt. Iwate and damaged a subalpine forest. All avalanches damaged many trees and terminated within the forests. In our simulations, the resistance of the forests to avalanches is simulated using a larger bed friction angle. Fitting the observations from the Makunosawa avalanche by trial and error, a bed friction angle of 13–14° in the non-forested area and of 25° in the forested area is obtained. We conducted simulations of the Mt. Iwate avalanches using the same method as for the Makunosawa valley avalanche, and obtained good agreement between observations and simulations. Simulations reveal that without the forest, the avalanche would have traveled at least 200 m farther than the forest's actual end in the Makunosawa valley, and at least 200 m and possibly up to 600 m farther on Mt. Iwate. This study therefore clearly shows that forests provide a braking effect for avalanches.