| Abstract: | The magnitude and causes of rainwash and runoff variability within small and supposedly “homogeneous” areas were investigated. Artificial rainfall (at 50 mm hr−1 for 30 minutes) was applied to twenty identical 0.0929 m2 (1 ft2) mini-plots arranged within a wetted annular 16.5 m2 in area. Despite the uniformity of techniques used for data collection, there was considerable variability in the rainwash and runoff data (coefficient of variation= 21 to 35% and 20 to 75% respectively) at the three locations in southern Ontario. In comparison with laboratory data, field rainwash variability was similar but field runoff variability was substantially higher. Soil strength parameters, surface roughness and microtopography, as well as aggregation indices, are considered to be the potential causes of the observed variabilities. Operator variance was found to be extremely significant in our study. It is suggested, therefore, that comparison of erosion data collected by different researchers must be conducted with great caution. |
