Soil erosion processes in sloping land in the east coast of Peninsular Malaysia

Abstract

Understanding soil erosion processes is essential in appreciating the extent and causes of soil erosion and in planning soil conservation. A comprehensive study was conducted on steep slopes on the east coast of Peninsular Malaysia where the rainfall pattern is monsoonal. Rates of rainfall and runoff, and soil loss, were accurately measured from four large plots of 1000 m2 and a bare plot of 20 m2. Instruments used include Parshall flumes, height recorders, a pluviometer and a runoff tipping bucket recording on a datalogger, with the associated computer hardware and software for data processing and analysis. Because of the slope of the land (about 18%) and the existence of large well-defined flow pathways, soil was largely eroded through the processes of entrainment and reentrainment. Soil loss and runoff were particularly high where the pathways were very pronounced. Other factors influencing soil erosion were disturbance to the soil surface, which produced easily entrainable material, and percent contact cover. The parameter β, calculated for a large number of events, was found to vary according to the availability of entrainable material. There was a gradual general decrease of β with time although most values were in the range 0.37 to 0.25. Suspended load was commonly more than 50% of total soil loss. Consequently, high chemical enrichment ratios were obtained. This has important implications on the reduction of soil quality through nutrient and organic matter losses.