Investigation of river stage simulation before and after bengoh dam construction: case study of Sarawak River Basin Malaysia

This research was conducted to study river stage behavior at Sarawak River before and after Bengoh Dam construction. The relationships of Bengoh Dam and Sarawak River stage are thoroughly analyzed and discussed based on four scenarios namely a) before dam construction, b) after dam construction and reservoir fully filled with water, c) after dam construction but reservoir empty, and d) constant flow release after dam construction. Besides, each scenario will be further analyzed with the operation of barrage gates at Sarawak River mouth, both in fully opened or closed modes. InfoWorks RS was employed to model Sarawak River using January 2000 hydrological data. The study demonstrated that after construction of Bengoh Dam, river stage level at Sarawak River at upper reach will be reduced and the flood issue can be mitigated. Besides, Sarawak Barrage also plays a significant role in influencing the river behavior. When the barrage gates are closed, the river stage level will rise to certain extent, which severely inundates multiple locations at the river downstream. In contrast, when the barrage gates are opened and sea level is lower than the river level, the river water will flow towards South China Sea at constant rate