A morphological model of Lake Dunstan was developed and used to better predict the future development of the sediment delta in the combined Kawarau/Dunstan Arms, to assess the change in sediment outflow quantity and composition over time and to reassess flood profiles based on future projections of the lake bed. A one-dimensional morphological model of Lake Dunstan has been constructed using the US Bureau of Reclamation’s SRH-1D modelling package. Steady-flow backwater simulations were run using 50 year and 100 year beds output from the 100 year projection simulation. These predictions are best estimates based on current knowledge but are subject to uncertainties in water inflows, sediment supply rate and gradation, and in key parameters such as channel roughness. We recommend continued monitoring of water levels and turbidity at current monitoring sites, along with regular survey of cross-sections and surface grain-size to provide ongoing data to update these predictions. In addition we recommend re-running the morphological model at 10 year intervals to update the estimates of projected flood levels. Several cross-section survey datasets have been used in this study. These datasets were all supplied by OPUS, and were sourced from the MIKE-11 model cross-section database. The representations of cross-section survey data within the SRH-1D model should therefore be identical to the survey data used in previous modelling studies using the MIKE-11 model. Using the calibrated model a 100 year projection simulation was run. Key predictions (from a February 2014 base) are: (a) The thalweg level at the Ripponvale gauging station will rise 2.6 m over 50 years and 4.7 m over 100 years with the rise occurring at a constant rate of 0.035 m/year over the 100 year period of the simulation. (b) A bed thalweg rise of 13 m at the Kawarau/Clutha confluence over the first 10 years, as the sediment tipping point passes the confluence, followed by a steady rise of 0.05 m/year over the remaining 90 years of the simulation. (c) The sediment outflow at Clyde Dam increases over time from an average of 168 kt/year over the first 20 years to 518 kt/year over the last 20 years (i.e. for year 80-100). Correspondingly, the trap efficiency for Lake Dunstan reduces from a 20 year average of 91% for year 0-20, to 72% for year 80-100. (d) The sand content of the outflow increases from 0.4% to 3.3% for years 0-20 and 80-100, respectively, and is almost completely very fine sand grade. We note, however, that it is likely that operation of the bottom sluice of the dam would lead to significantly higher outflows of sand than predicted by the model, as the model does not provide any representation of where vertically or horizontally in the cross-section the outflow occurs. Steady-flow backwater simulations were run using 50 year and 100 year beds output from the 100 year projection simulation. Key results are: (e) The flood level at Ripponvale for a 3200 m3/s flow at Clyde Dam is predicted to be RL 202.92 after 50 years and RL 204.53 after 100 years (c.f. RL 200.49 currently). (f) For the same flow at Clyde Dam, and for a headwater level at Clyde Dam at the design flood level of 195.1 m, the flood level at the Kawarau/Clutha confluence is predicted to be RL 198.95 m after 50 years and RL 200.76 m after 100 years (c.f. RL 195.34 m currently). (g) Flood levels in the Upper Clutha Arm at the Cromwell end of the lake are just 0.05 m higher than at the Kawarau/Clutha confluence for a 3200 m3/s total flow.