The effect of slope angle on splash detachment in an unmanaged Japanese cypress plantation forest

Abstract

AbstractA field investigation of the effects of rainfall and slope angle on splash detachment was conducted for 5 months, using 27 splash cups in a Japanese cypress plantation in southern Japan. The unit, kinetic energy of throughfall (J m−2 mm−1), was found to be constant and independent of rainfall intensity, indicating that splash detachment can be related to both throughfall intensity and soil slope. The linear correlation coefficient was highly significant for both the maximum throughfall intensity over 1 h (RI1h) and the average splash detachment of all splash cups, although individual cups varied widely. No consistent relationship was found between the splash detachment rate and slope angle for individual periods. This variation in the relationship between splash detachment and slope angle was attributed to the effect of soil crusting and ponding on splash detachment. Splash detachment on a gentler slope (14° ) exhibited a strong relationship with the maximum throughfall intensity lasting for short periods of 10–30 min. In contrast, the splash detachment from slopes > 35° highly correlated with the maximum throughfall intensity over 3 h. This suggests that a longer period is required to prevent the splash detachment due to ponded water on steeper slopes. On gentler slopes, prolonged rainfall may result in a higher ponding depth, thereby reducing raindrop impact and causing less splash detachment. Thus, under forest canopies, the effect of slope angle on the rainfall parameter should be incorporated into future splash erosion models. Copyright © 2010 John Wiley & Sons, Ltd.