The Orange River Re-Planning Study (ORRS, 1997) recommended that the proposed Noordoewer/Vioolsdrift Dam (NVD) site be further investigated as possible dam development downstream of Vanderkloof Dam, in the lower reach of the 2200 km long Orange-Senqu River. The Lower Orange River Management Study (LORMS, 2005) recommended that a re-regulating dam be constructed at the NVD site on the border between Namibia and South Africa in order to increase the availability of water to meet both the future human and ecological water requirements for the Lower Orange River and the river estuary. This paper addresses the NVD feasibility study findings based on the joint study by Namibia and South Africa related to sedimentation. The sedimentation investigation consists of two phases i.e. (1) the determination of the sediment yield at the proposed NVD site and (2) the reservoir sedimentation hydrodynamic modelling, including the flood level simulations due to sedimentation and the feasibility of flushing sediment from the reservoir. From the sediment yield analysis, the proposed long-term sediment load at the NVD site is 16.4 million t/a. Based on the 2D hydrodynamic modelling, the proposed NVD reservoir would have 47% and 77% of the original storage capacity after 100 years of operation, for the 70 m and 90 m high dam scenarios respectively. The reservoir traps 97 % of the sediment load. Reservoir sedimentation mitigation measures were investigated to extend the life of the dam, based on ICOLD (1999) guidelines. Simulations were carried out to evaluate reservoir drawdown flushing during floods and local pressure flushing at the dam outlet for irrigation. Based on the expected relatively large sustainable equilibrium FSC of 70 % of the original FSC for the NVD project, it is proposed that the 70 m high dam (or a lower dam), with a smaller dead storage for sedimentation, is designed with drawdown flushing during floods.