THE USE OF RAINFALL SIMULATION TESTS TO ASSESS THE INFLUENCE OF VEGETATION DENSITY ON SOIL LOSS ON DEGRADED RANGELANDS IN THE BARINGO DISTRICT, KENYA

The relationship between cover density and soil loss under simulated r ainstorms of 30 and 60-minute duration and 33 mm h(-1) intensity was i nvestigated. Soil loss varied from 0-7.3 g m(-2) for cover of 55-95% a nd reached maximum values of over 80.0 g m(-2) (30-minute storms) and 140.0 g m(-2) (60-minute storms) for cover of 25% or less. A critical threshold occurred at 55% cover below which erosion rates rapidly incr eased to over 15.0 g m(-2) (30-minute storms) and 30.0 g m(-2) (60-min ute storms) during single rainstorm events. Storm duration and frequen cy were important determinants of erosion over more prolonged time per iods. Total calculated soil loss for an 18-year period under 55% cover for frequent 30-minute storms (frequency: 3-4 times a year) was 6 tim es that for infrequent 60-minute storms (5-year return period).