What would happen to his memories if Jonas were to fall into the river and drown accidentally in "The Giver"?
The Giver tells Jonas that "memories are forever, and that if he were to fall into the river and drown accidentally, his memories would come back to the people. Since the people would have been completely insulated from the emotions and feelings associated with the memories, they would be woefully unprepared to deal with them. The sudden rush of memories would wreak havoc among the people in the community.
The Giver relates that this is what happened when Rosemary, who was to have been the Keeper of Memories before Jonas, was unable to handle the pain of the memories and asked for release. Rosemary was the Giver's daughter, and her loss was devastating to the old sage. The Giver was so overwhelmed with his own grief and anger at Rosemary's death that he didn't even try to help the people through the turbulent time when the memories returned to them unchecked.
The Giver reflects that he has already transferred to Jonas many more painful memories than he gave to Rosemary. If Jonas should die and his memories should return unchecked to the people, the results could be doubly devastating (Chapter18).