最上川における砂レキ流動に対して盆地・峡谷のもつ意義
1974 年 26 巻 3 号 p. 123-129
詳細
1974 年 26 巻 3 号 p. 123-129
The writer surveyed the river bed sediments in the Mogami River at 17 stations (Fig. 1), where he gathered the sands and gravels of one square metre surface area and 30cm depth at the water edge and surveyed their lithology (on those of more than 64mm in diameter) and diameter.
The lithology and the diameter distribution of gravels are shown in Figs. 3, 4 and 5.
These figures show that a lot of sand and gravels are furnished in the gorges and deposited in the intermontane basins downstream.
Based on the lithology of gravels the writer divides the Mogami River into 6 parts, i. e., (1) The Matsuzawa River in Yonezawa Intermontane Basin, (2) The Shirakawa River and the main Mogami in Nagai Intermontane Basin, (3) The River course in Arato Gorge and Yamagata Intermontane Basin, (4) River course in Oyodo Gorge and Obanazawa Intermontane Basin, (5) River course in Shinjo Intermontane Basin and (6) Mogami Gorge and Shonai Plain.
From the view point of river bed sediments, the Mogami is a combination of six different reaches, which alternate erosion and deposition respectively.
The clear differences in lithology and diameter of gravel of the six reaches show that the depositional function of the intermontane basin is very important.
