Effect of river cleaning on lowland drainage in South‐Eastern Sumatra

Abstract We study a tropical river in South‐East Sumatra, where land drainage in the coastal zone has resulted in subsidence and increased flooding risks, exacerbated by sea tides. The novelty of this research is in determining the effect of tide on the lowland drainage system for forestry in a coastal tropical region and the impact of river cleaning on flood management. Five monitoring stations were set up along the Lebong Hitam river and its primary channels to observe flow characteristics, water level, and bathymetry. The results show how the tide effects water level in the river and the adjacent drainage area with Eucalyptus plantations. Cleaning of the river had a significant effect on each station and increased the discharge and velocity by more than five times and reduced the water depth by more than 40%. In light of this research, it can be concluded that the cleaning up process improves flood risk management by decreasing the water level and increasing the discharge and velocity at each of the upstream stations. The cleaning did not have a significant effect on downstream sections of the river where sea levels control the water level in the river to a large extent. The work provides an analysis of tidal river and provides recommendations for current and future drainage and water management.