FORCE =1 



FigiATe 4 . — The reso lution of a 

 vertiaat unit veotor force of 

 raindrop imyaot striking an 

 inotined surface. 



Then : 



where : 



And: 



where : 



Pf = Vf Sin 



Pf = magnitude of the force parallel to the slope; 

 Vf = magnitude of the force vertical to the slope; and 

 = slope angle, degrees. 



Nf = Vf Cos0 



Nf = magnitude of the force normal to the slope. 



EQ(1) 



EQ(2) 



The soil splash resulting from the normal component is assumed to be displaced equally 

 up and down the slope. Therefore, the downs lope component of soil splash resulting from 

 a unit force of raindrop impact is expected to be: 



D 



Sin0 + 1/2 Cos0 



EQ(3) 



where ; 



Sp = the proportion of total soil splash moving downhill 



It is interesting to note that EQ(3) predicts that virtually all soil splash resulting 

 from vertical raindrop impact will go in a downhill direction on all slopes equal to 

 or greater than 37° (75-percent slope). However, this hypothesis was not tested. 



The total amount of soil splashed from the soil plot was measured for each of the 

 18 test runs. EQ(3) was used to calculate the downslope component of the measured 

 total splash. These data were then analyzed by multiple regression methods. Total 

 calculated downslope soil splash was used as the dependent variable. The independent 

 variables were the same as those for the soil splashed into the bottom pan (i.e., slope 

 steepness, rainfall intensity, soil bulk density, and the proportion of total soil 

 particles and water-stable aggregates between 61 and 2,000 microns in diameter). The 

 resulting regression model (figs. 5A and 5B) explains over 92 percent of the variance 

 associated with the calculated total downslope soil- splash erosion, (R^=0.924). 



8 



