THE INFLUENCE OF THE NEW LRT PIER TO THE SEDIMENTATION PATTERN AROUND AMPERA BRIDGE IN MUSI RIVER, SOUTH SUMATERA, INDONESIA

Abstract

Sedimentation rate, which is the most important parameters of the inland water way
performance like Musi River becoming one of a major research topic in Indonesia. The influence of
additional pier for the new LRT Bridge constructed parallel to Ampera Bridge to the sedimentation pattern of
Musi River was discussed in this paper. Currently, as most of the rivers in Indonesia, a complete field data
observation of discharge, sediment characteristic is a luxury one to have. That’s why mathematical model,
supported by eligible limited field measurements for model calibration and verification, is commonly used to
predict the above parameters. Hydrometric survey of water level, sediment samples (both suspended and bed
sediment), velocity and bathymetry were conducted to get instantaneous field data. Based on the comparison
of two bathymetry map with difference periods of measurements, it was found that the sedimentation rate,
was different for high and low tide. Tank model of Sacramento and USLE were used to respectively generate
synthetic river discharge and soil surface erosion rate. Hydrodynamic model of SMS 8 was used to predict
annual rate of sedimentation. Good comparison of the field measurement and SMS model results was found
for current and sediment pattern. The maximum sedimentation occurs during the high tide where the
backwater was generated by sea intrusion. The New LRT pier increase the impact of river contractions for
both maximum velocity around the Ampera Bridge up to 1.5 time and sedimentation rate behind the pier
group of the bridges.