|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1997 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)
To estimate the amount of soil loss, a number of soil loss equation, such as USLE equation, have been proposed. In order to raise the applicability of the soil loss equation, a number of indoor and outdoor experiments and observations have been carried out. As the experiments have been conducted, the effect on soil loss have been analyzed in terms of vegetation, field-characteristics, and surface run-off by the following methods. With the collected data of soil loss in different cropping-piots under natural rainfall and artificial rainfall, the applicability of the equation been investigated.
In this equations, the rainfall factors has been included considering the mean number of rainfall energy, the maximum of rainfall. But to predict the soil loss precisely in case of a country like Japan with variable distribution of rainfall, It is important to consider variation of each and every type of rainfall. In this study, amount, energy of rainfall have been calculated and analyzed in detail, The result of analysis indicates that Energy of rainfall are more related than amount of rainfall to soil loss,
Next, to investigate the relationship between the rill patterns and soil run-off. Experiments were carried out by supplying artificial rainfall. In this experiment, the time variations of soil run-off were measured, and the relationship between the forms of rill patterns and soil loss was discussed. The effects of surface flow and width farmland on the soil loss and the rill shapes, changing the slope width into three different dimensions, some indoor experiments were carried on to investigate the effect of slope width on the rill shapes. From the experiments, it was found that in case of the identical slope length, the amount of soil loss per unit width with an increase in slope width had a tendency to be constant.