Conclusion

A quantitative assessment of average annual soil loss in Ben Ahmed watershed was made with GIS based USLE equation considering rainfall, soil, land use and topographic datasets. The average erosion rate in Ben Ahmed watershed ranges from 0 to 88 t/ha/year with an average of 1.1t/ha/yr and a standard deviation of 3.7t/ha/yr. The rate of soil erosion varies highly within the landscape mainly due to the changing of land use pattern, topographic abrupt change and soil type distrubution. The results indicate that 94% of the total area watershed lands are subject to low losses, while 5% is severely eroded with rate erosion soil ranging from 10 to 88 t/ha/year. Moreover, rate of soil loss from different sub watersheds is mainly dependent on C, LS and K factors.