富士川の河床変動に関する研究

Abstract

Fujigawa River has a steep slope with a large amount of sediment discharge andmuch river bed variation. Observations for the variation of the river bed and of thetalweg have been conducted since 1918 to the present time. Also the grain-size distrib-utions of the sediment along the river course and below the stream bed surface wereobtained.In this paper, the author conducted the various analyses for the above data includinga spectral analysis, and revealed some interesting characteristics concerning for the sedi-ment distribution and the river bed variation. Main results are as follows, Torrentsinto the main river have large effects on the sediment distribution along the main river, andthe sediment from the torrents does not follow to the relation between the grain-sizeand the shear velocity found in the main river.River bed variations are composed of three scale components; dunes, bars and thelarger scale configuration.The scale of dunes is less than the river breadth, but has large amplitude which hasan important effect on the bank protection. Two or more prominent wave length ofdunes were obtained by the spectral analysis. Bar is due to the meander and the length(a hafe of meander length) is about 3-4 times of river breadth. The larger scalecomponent may be due to the variation of the river geomorphology.Variation of talweg is rather random, but the mean value reveals the periodicvariation along the river course with a wave length corresponding to the bars.The standard deviation of talweg from the mean value which is a measure of the riverstablization is rather large but the value decreases at the large deviation from the rivercenter.