Hi- Welcome to Just Answer and thanks for your question.Since the end of World War II, West Maui has lost 2.8 miles of beaches to erosion, with Kahana being one of the areas of the worst erosion. The rise in sea levels has almost doubled in the last 10 years. Estimates of sea level rise by the year 2100 is between 1 to 2 meters (~3.28- 6.5 feet).
To see a pictoral reprersentation of the effect, see the following link: http://www.soest.hawaii.edu/hmrg/FloodingOahu/stepbystep_maui.phpThe above information points to the fact that the timeframe is more like several decades rather than just one. However, the process does seem to be speeding up. So it probably will push the sand back a lot, but not for awhile. Remember though, all this is based on estimates. There are no certainties in predictin g the effects of global warming.