Sedimentation Rate and Sediment Accumulation at the Estuary of Rokan River, Indonesia

The objective of the study was to analyse the sedimentation rate and sediment accumulation at the estuary of the Rokan River. Sediment samples were collected from 3 sampling points, i.e. Southern, Western and Northern of Berkey Island. The samples were then analysed using 210Pb radioisotope of the alpha spectrometer. The bottom of the Rokan River estuary is dominated by fine silt. It was recorded that sedimentation rate in Southern, Western, and Northern of Berkey Island were 0.3, 0.22, and 0.28 cm/year, respectively. The accumulation of sediment in each station was as follows; 3.13, 2.88, and 3.42 ton/ha/year. The age of sediment in the Southern Berkey Island was 23,71 years at depth 14 cm, Western Berkey Island was 64,26 years, and in Northern Berkey Island was 26,59 years. Sedimentation rate inside was higher than outside of the estuary. Higher sediment accumulation was noted at the outer part of the estuary compared to the inner part. The sediments found in the central part of the estuary are older than those inside and outside.