Effect of change of channel width in the downstream of the check dam on controlling sedimentation in Mrica Reservoir

The increasing sedimentation of Mrica reservoir shows that the sedimentation control has not been effective. The sedimentation control has been made include the disposal of sediments that settle in the reservoir by dredging or flushing. However, the results are not optimal. This is caused by the large volume of sediment entering the reservoir each year. The controlling volume of sediment that goes into the reservoir has also been carried out by conducting a watershed conservation program and building a check dam in the upstream Mrica reservoir. However, the existing check dam is still less effective in controlling sediments, especially suspended load sediments, that are transported in the river. Therefore this study was carried out by adopting the sediment trap concept to deposit sediments that escaped from the check dam. This study simulated changes in the width of the downstream channel of the check dam by three variations using HEC-RAS. There was a width of 20%, 40%, and 60% wider than the initial width. The results showed the effect of changing the channel width on volume sediment deposited. Based on the results of the study, the change in width to wider than the initial width could increase the volume of sediment deposits.