From the consideration of simplified mechanism of debris transport and hydraulic geometry of stream channels, it is derived that the gradient of valley bed can be expressed by a power function of the length of stream channel from the divide. The exponent represents the concavity of lougitudinal valley profile. The applicability of the power function to actual valleys is confirmed by the results of morphometric measurements of 30 valleys in mountain basin. The values of the exponent obtained by morphometry are between -0.5 and -0.7 in the upper reaches of valleys, while in the lower reaches the values are less than -1.0. The gradiedts of valley beds where this discontinuity occurs are 10°-14°. In the upper stream mass movement is a dominant process, and in the downstream tractive force of water flow is a main agent. The difference of the concavity of valley profile is inferred to be due to this difference of transporting agent.

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Alternating Bar is one of the most general river bed forms in Japan, and its downstream movement is the very important character. And in swift stream rivers, groundsels are constructed in order to prevent river beds from erosion.
Therefore, the influence of these groundsels on the formation and the movement of ‘Sarekitai’ whs investigated by experiment, then clarified as follows.
1) When a groundsel has no fall or a small one between its upper and lower sides: Alternating Bars are formed continuously, and move downstream having no influence of the groundsel.
2) When a groundsel has a large fall: Alternating Bars are forced to retard just at the lower side of the groundsel, however, they are still formed continuously and move downstream.
3) When a groundsel has a sediment control function: At first, sand is accumulated at the upper side of the groundsel. On the contrary, sand is dug up at its lower side, so that Alternating Bars cannot be formed there. When the upper side is filled up with sand, Alternating Bars are begun to form continuously crossing over the groundsel.

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