Abstract
Characteristics of snowcover-snowmelt, freezing-thawing, runoff and soil-loss were investigated by a slope lysimeter for defining soil erosion at the snowmelt and thawing period were investigated using observations. The results are summarized as follows:
1) Runoff percentage of snowmelt at the freezing plot was higher than that at the unfrozen plot, because of the ground depression intake due to freezing. Also, the percentage at freezing grassland was higher than that at freezing bare soil. It is supposed that the intake rate of grassland is higher than bare soil due to the influence of grass roots.
2) Soil loss of the frozen bare lysimeter with snowmelt is more than 13 times the unfrozen lysimeter. It is thought that the permeability and erodibility of soil were changed with ground freezing.
3) Soil erosion was controlled efficiently by grass, that is, the soil loss from the grassland was 1/6 times than that of bare soil under the freezing condition. In addition, a similar effect was recognized even for the unfrozen condition.
4) Runoff of the unfrozen lysimeter was much more than the prefrozen lysimeter after snowmelt and thawing. It is because the permeability of ground increases due to freezing and thawing.
5) Soil loss changes with rainfall were normal. Namely the soil loss was between the prefrozen and unfrozen for rainfall of small EI30. For large EI30, the soil loss after thawing was much more than the unfrozen plot. This is due to the increasing of the surface soil erodibility through freezing and thawing.
