1954 Volume 63 Issue 1 Pages 25-32
During the cycle of erosion and sedimentation, there should be a volumetric equilibrium between them. The writers have assumed the volume of sediments in basins is equal to the void space between the summit level and the present topography at each drainage area. In that case, the volume of the youngest Tertiary formation (Shibikawa stage of Plioceneage) at Shonai, Shinjo and Yamagata basin is nearly equal to the erosion volume of the topography covered by the Mogami River. In other words, the formation of the present topography has just begun at the latest Pliocene. Further writers found a key to solve the problems to determine the stage of a geomorphological development by analyzing the present topography. Lastly, there is shown a volumetric relation between the river-length (l) and erosion volume (v) in this district, v = 0.019l2 + 0.12l.