Inquiry on Natural Levees

Abstract

Tatsuo WAKOThe author has exmained the explanations on natural levees from several text books, and reached the following results. (1) As far as Japanese literatures are conerned, the term "natural levees" is often used without distinction between true natural levees and point bars. (2) Also in Japan, it is often said that the natural levee areas are situated between fan areas in the upstreams and the delta areas in the downstream. If so, it is necessary to discuss the forming and modifying processes of natural levees not only from the view-point of the hydrological study of stream regime but from the chronological study of the flood plain as a whole. The followings must be studied: the mode of erosion in the source areas of stream load, the relation of the extended river development and the flood plain formation with the regression or the transgression of the sea. Beside such a treatment on the idea of geological stage, the ages of parts of flood plains must be known, because it seems to be true that the germ of a natural levee is brought about by the occupation by scrub on certain parts of the flood plain as explained by Lange et al, (1962).