Deep
The force of a tsunami is enough to put a gash in a tree about pi (3.14) feet deep. Tsunamis are pretty powerful, so the force of the water alone is enough to cut into a tree several feet deep.
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ふか
None
Some tsunamis cut so deep that they flat out chop the tree right off its stump. In areas like this, you have to be careful not to bang a shin (しん) on them. These stumps are right about shin height, so you want to be cautious when walking around them as to not injure yourself.