Preliminary Modeling of Characteristics of Current and Batimetry in the Confluence of Mahakam River and Karang Mumus River

Abstract

The movement of currents at the confluence of the Mahakam River and Karang Mumus River is highly influenced by tides and fluvial discharge can result in the movement of mass water. Research at low tide on January 21-22, 2019 at Spring tide. Data used current velocity, current direction, depth and bathymetric map from DISHIDROS of Indonesian Navy. The study aimed to compare the contours of the river measured against bathymetric map from DISHIDROS of Indonesian Navy and the current and vertically and horizontally flow patterns. Research used quantitative methods. Vertically and horizontally current distribution using Surfer software 11. The results of recording bathymetry data compared with bathymetric map from DISHIDROS of Indonesian Navy. the results of the study showed that the vertical velocity from upstream. they were before the confluence of rivers reached 0.11 m/s where the upper layer was down, the middle layer and the bottom layer were horizontal. Meanwhile, the current velocity at the confluence of rivers vertically showed the upper layer and bottom layer towards the middle layer as if it were mixing with its ranging from 0.02 - 0.32 m/s. while, the vertical velocity was larger in the downstream range of 0.04 - 0.38 m/s. the current velocity from upstream reached 1.1 m/s horizontally. they entered confluence of rivers a two-way flow was present. The flow on the right side of the curve was caused by flow output from the Karang Mumus River at a velocity of about 0.8 m/s, the flow on the left side still followed the river flow but the velocity decreased slightly 1 m/s. Then, in the downstream side by side the flow occurred until it merged into the straight part of the river channel from the velocity of 0.8 m/s to 1 m/s. the declining flow velocity at the confluence of the river can occur sediment deposition. It was also seen with bathymetry measured against the DISHIDROS map in 2011 where there was a decrease in depth or deposition along the confluence of rivers.