Abstract
This paper discusses effects of cover plants on surface runoff on the basis of hydrological observations for three years in five plots. Four of these plots were cover-plant plots vegetated with Cynondon dactylon Pers., Dichondra repens Forest. and Artemisia princes Pampan., and the other one was a bare-surface plot. Comparison of runoff records in these plots showed that cover plants reduces both total runoff and peak runoff. The total runoff from cover-plant plots was 26-39% of that from bare-surface plot, and the peak runoff from the cover-plant ones was 24-35% of that from the bare-surface one. A rainfall-runoff model was developed, in which overland flow was described as Manning type and infiltration process was expressed by the Horton's equation. Calculated hydrographs by the model were in good agreement with observed ones. The results of rainfall-runoff analysis using the model showed that infiltration in cover-plant plots exceeded that in the bare-surface plot for the same rainfall pattern. The asymptotic infiltration rates in cover-plant plots were about four times as large as that in the bare-surface plot. Besides, the results showed that occurrence of surface runoff in cover-plant plots was less frequent than that in the bare-surface plot, which suggests that cover plants suppress the occurrence of surface runoff.
