EVALUATION OF SOIL EROSION AND SEDIMENTATION PROCESSES OF PANGASUGAN WATERSHED IN BAYBAY, LEYTE, PHILIPPINES

The main problem of most watersheds in Leyte is the conversion of ri parian vegetation to conventional agriculture which causes environmental concerns such as soil erosion, sedimentation and nutrient loss. This study was conducted to evaluate the processes of soil erosion and sedimentation and assessed the amount of nutrients lost due to erosion in the Pangasugan watershed. Three study sites having different land use systems were chosen in the lower, middle and upper portions of the watershed for the determination of soil erosion rate, sediment yield, nutrient losses and associated environmental factors like slope, vegetation cover, soil erodibility and rainfall. Results showed that soil erosion was highest in the kaingin (slash and burn) land use system followed by the coconut monocropping and the lowest in the intact forest. The average soil erosion rate of the watershed is 38.4 t ha-1year-1 which is much higher than the accepted tolerable value of 11 t ha-1year-1. Sediment yield was also highest in the kaingin land use system which agrees with the soil erosion rate. Vegetation cover and land use management, rainfall, soil erodibility and slope appear to be the factors influencing the soil erosion and sediment yield in the watershed. The results imply that high erosion rate and sediment yield are greatly dependent on the type of land use system. Maintenance of good vegetation cover should be practiced to minimize soil erosion rate, sediment yield and nutrient loss