ElRay L. Christiansen says earth was "depopulated" by the Flood.
ElRay L. Christiansen, Conference Report (April 1961): 72–73
According to the writings of Moses, the history of the world from the beginning to the end was revealed to Enoch when Enoch was permitted to look upon the world and see it as it was in the days of Noah, as it was in the Meridian of Time, and as it would be in the last days, or the days in which we now live. Enoch beheld all of the inhabitants of the earth. He saw that after the flood had depopulated the earth, because of wickedness, it was after a time inhabited again. But then he saw that after a time, men were again forgetting God and were rebelling against the truth. He saw the Savior in the Meridian of Time lifted up on the cross as a sacrifice for mankind and as the Redeemer of the world. When Enoch saw all this, he wept. And he beheld also that Jesus wept. And Enoch asked of him, "How is it that thou canst weep, seeing thou art holy, and from all eternity to all eternity?"
"The Lord said to Enoch: Behold these thy brethren; they are the workmanship of mine own hands, and I gave unto them their knowledge, in the day I created them; and in the Garden of Eden, gave I unto man his agency" (Moses 7:29, 32)
The Lord went on to explain to Enoch by saying that he and the hosts of heaven wept because of the rebellion of mankind, nevertheless, Enoch was assured that the Lord would come again in the last days, and that before his coming he would cause righteousness and truth to sweep the earth as with a flood, to gather out his elect from the four corners of the earth. (Moses 7:62.) Surely that has been going on ever since the Church came into being.