Studies on the improvement of Rainball simulator and effective experiments of soil erosion

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K.Hosoyamada and K.Kakita newly developed a rainfall simulator "hanging pressurized spray type" and showed the relations between a pressure of the reservolrs,open and close time of electro magnetic valves,rainfall intensity, falling velocity of raindrops and raindrop diameter.Next,they calculated the rainfall energy in each cases. On the erosivity factor R of natural rainfall,they showed that the results of calculation by convenient method were highly correlative to the ones by original calculation.T.Fujiwara et al. showed the experimental results of radial and angular distribution of soil splashed by a waterdrop impact.As a result of statistical analysis of the experimental data,it became clear that radial angular distribution density fuction was expressed by the exponential type function, <GAMMA>type respectively.T.Kusaka investigated the application of soil loss calculation for the actual field compairing the results at test plots with the ones at experimental laboratory.Next.he obtaind the relations between rainfall and surface runoff statistically and set up an estimate equation.N.Minami et al. Investigated the properties of the non-pressurized rainfall simulator consecutively and obtained the local distribution and the changing range of rainfall and calculated the rainfall energy.K.Onaga showed that rainfalls with certain intensity at Okinawa has high energy.Moreover he investigated the soil properties(grading,structgure etc.)and cropping systems,and summarized the actual conditions and the countermeasures for soil loass.Y.Shiotsuki calculated the rainfall energy by means of regenerating the distribution of raindrop size using the data of 10 minutes rainfall.Moreover he found out that the rainfall energy at a concentrated rainfall is gained by means of extrapolation of calculation equation of the rainfall energy based on space density N_d of raindrops.