Absolutely. If only the natives had been more disease resistant and put up a better fight, the area might have developed more on the European model, farms down on some of the best agricultural land in the world, with civilization up in hilltop fortifications to better keep out the looters and marauders. The gold rush might have still brought in a critical mass of crazies though. Silicon castles.
The planet changes sea level up and down by over 100 meters all by itself (and the solar cycles). Humans have migrated miles back and forth with the sea level changes though at least a few ice ages already. They'll just have to figure out how to keep on doing that.