Flood issue in Samarinda almost surrounding every year, especially in the rainy season (October – April). Its issue depends on the several factors such as drainage condition,topographical area and also the problems of Karang Mumus river. This paper focused on the river problem. This river has decreasing capacity caused by constriction. Its affected by a lot of people live on the riverbank area and the worst of it is impossible to relocate all of them. In this study, we tried to analyze how to reduce the discharge. The analysis covered by hydrological analysis by using several scenarios. Most of the results exhibit the discharge of the river decrease than the current condition. The discharge decreased until 59,2% after scenario was applied.