Dissection Types of River Terraces in the Ayashi Basin, Miyagi Prefecture

Abstract

In the Ayashi Basin, four levels (I-IV) of river terraces develop along the Hirose River 230-90m in height. They are dissected differently depending upon valley types which are distributed according to the topographical locations. 1) Terraces suffered lateral erosion of the main stream are reduced by way of cliff-retreat, without any dissecting valley (III, IV). 2) Near the margin of terraces, far from the main stream, Kerbtal develops to split the flat surface. 3) The central part of the terrace, where the Muldental-type is predominant, has been transformed into a rolling surface, to the extent of losing the flatness of terrace surfaces (I, II).