The relation between river terraces ane annual rings of trees on the terraces in the Ashiarai velley is discussed in this article.
The Ashiarai valley is one of the valleys of Mt. Yake which is an active volcano and takes place in the southern part of the Northern Alps of Japan.
Mud flows have occured frequently and they have worn the base rock and deposited as a terrace in the valley. There are some river terraces which deposited as steps in the trough of the valley. Seven river terraces are made clear by investing the relation between the comparative height and annual rings of trees on the terrace and have shown the forming age of the river terrace. For instance, b terrace was formed five or six years before, because five or six years old trees have grown on b terrace, and so on as illustrated in figure 1.
Also recent history of the Ashiarai valley since more than thirty years is illustrated in figure 1, and the movement quality of the deposit material is calculated such as table 3.
These events may teach us the continuity and periodicity of the sediment production and erosion of the Ashiarai valley such as figure 5. The erosion periodicity of the Ashiarai valley is more than thirty years and the movement quality for these years is more than 250×10⁴m³.

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