Flooded Settlement

looking up the arrow head lake from 5min through the ferry crossing at galena bay in BC canada.
while on the ferry I overheard a conversation about how at one time the land under the mountain on the right used to be above the water a far way, so much so that it was a valley and had a native settlement that was on the riverfront. the river was flooded and damed several times so now the water level is 30-50 meters from where it used to be.