The impact of the Stella Development Plan, specifically proposed wharf, reclamation and channel extensions, on the hydrodynamics of Tauranga Harbour were investigated using a depth-averaged barotropic numerical model, Delft3D. The model was calibrated and validated using field observations collected in March 2017 after the completion of capital dredging in 2016. The model calibration and validation scores for water level were consistently excellent. Calibration and validation scores for velocity were mostly excellent, but some locations outside the region of interest had lower scores; but are not considered to impact on the reported results. Water elevation changes resulting from the proposed extensions were less than the calibration and validation errors, and indicate negligible impact on tidal elevation and timing. The main impact of the extensions was a large decrease in flow speed within the deepened channel in Stella Passage. No signficant changes were evident beyond the extent of the channel extension, although there were some slight changes in flow direction associated with the abrupt depth transition into the new dredged channel. Comparison between the harbour hydrodynamics before and after the 2015/2016 capital dredging indicated that previous studies that investigated potential impacts of port and marina developments adjacent to Stella Passage will still be valid beyond the immediate area of wharf and channel extension.