1986 年 59 巻 8 号 p. 470-479
Measurements of downward-erosion rates in rill and interrill areas were carried out in a small bare land area of the subtropical Okinawa island (Figs. 1 and 2). The bare land is composed of BC layer of red soil derived from phyllite.
Interrill-erosion rate in the first-order divide segment has no consistent relationship to the divide segment length and the divide segment gradient (Fig. 4 and Table 1). This indicates that the erosive action is almost uniform in the first-order divide segment of interrill area.
Rill-erosion rate, Er, increases with increasing total rill length, and the rate of increase becomes lower as total rill length increases (Fig. 8 and Table 2). Figure 9 shows that Er also increases parabolically with an increase in the product of rill catchment area and rill gradient. On the basis of the assumption that rill discharge is proportional to rill catchment area, the result shown in Fig. 9 suggests that Er per unit total stream power decreases with increasing total stream power in a downstream direction.