Analysis of erosion and sedimentation in predicting the life time of the Cieunteung Retention Basin

The high rates of erosion and sedimentation as the impacts of changes in land use cause the problem of sedimentation. The aim of this research is to analyse erosion and sedimentation in the Upper Citarum sub-basin, which will impact the life time of the Cieunteung retention basin. The SWAT model was used to simulate the hydrological process and erosion mechanism by using the formula of MUSLE. Based on the results of simulation data, the highest average erosion equalled 1, 094 tons/ha/year in 2013 while the lowest average erosion equalled 71.16 tons/ha/year in 2009. The results of SWAT model calibration in 2008-2018 were R² = 0.89 and NS = 0.95, which means the model performance is categorized as very good. The simulation results showed the anticipative indicators of watershed disaster, as the erosion hazard index in terms of land cover and the coefficient of river regime in terms of water availability, have a very close relationship and positive correlation with the average of R² = 0.8. The incoming sediment to the Cieunteung retention basin is 105, 418 ton/year or 72, 551.961 m³/year. By using sediment trap efficiency with a value of 4.37%, this research estimated that the dead storage capacity of 113, 670.3 m³ will be filled with sediments in 35.87 years. Furthermore, the long-term retention basin conservation effort by land terracing can reduce total sediments by 22% to 81, 948 tons in 2018, and thus the life time of the Cieunteung retention basin becomes 46.15 years.