Erosion of Selected Hawaii Soils By Simulated Rainfall

Abstract

Abstract Erodibilities, or K values of the universal soil loss equation, were determined for ten soils representing five soil orders on the islands of Oahu and Hawaii. Two successive simulated rainstorms were used, each with an approximate intensity of 6.35 cm/hour and duration of 2 hours. Values obtained covered the wide range from 0 to 0.60 metric tons/ha per metric erosion index × 0.00774 (tons acre ‐1 erosion index ‐2 ) 3 and, in most cases, were higher for the second (wet) than for the first (dry) storm. Erodibility values for cropped Oahu soils, belonging to four soil orders, ranged from 0 to 0.26 for dry storms and from 0.001 to 0.41 for wet storms. Values for volcanic ash soils on Hawaii, belonging to only two orders, had the considerably wider range of 0.08 to 0.60 for dry storms and 0.07 to 0.51 for wet storms. Three of these soils exhibited essentially the same erodibility for dry and wet conditions. Dry and wet values were combined to calculate a weighted mean erodibility for each soil based on the distributions of natural rainfall throughout the year at the test sites. The weighted erodibility of a soil at a given location was in general, inversely related to the amount of natural precipitation at that location.