This paper aims to evaluate the efficiency of dredging scenarios in Malun Stream by using a CCHE2D
hydrodynamic model. The dredging scenarios were: do-nothing, dredge at the main stream with a compound cross-
section, and dredge at the confluence of the Malun Stream and Lanyang River. Considering the different depths of
dredge at the confluence, there were six dredging scenarios investigated in the present study. Through the simulation
of the bed changes in a flood event, the aggregation of the dredging areas was used to evaluate the efficiency of dredging scenarios. The verification of the CCHE-2D model showed the Modified Engelund & Hansen formula with the adaptation length equal to 1000 meters successfully represented the bed changes in the study areas. The simulation results showed the average height of aggregation was about 1.5 meters near the Malun Bridge in the do-nothing scenario. The corresponding value of the dredge at the main stream increased to 1.7 meters, because the sediment was trapped in the dredging areas. Near the Malun Bridge, this resulted in a decrease of the area of the cross-section and a corresponding decrease of ability to pass flood level. However, the dredge at the confluence showed an increase of flow velocity and ability of sediment transport. Moreover, the height of aggregation decreased with the increase of dredging depth. With the dredging depth ranging from 1.5~2.0 meters, the height of aggregation was less than 1.0 meters. The dredging at
the confluence of the Malun Stream and Lanyang River was found to be the most effective dredging scenarios among
the one studied here.
Keywords: Hydrodynamic model, dredge, efficiency, Malun stream