What would happen to the memories if Jonas fell in a river and drowned?

As Receiver-in-Training, Jonas is tasked with not just containing all the memories of the community but also all of the emotions. When the novel first opens, the reader is unaware that the community is built on only law and order and practicality; as the story progresses and more is revealed, primarily through interactions the Giver has with Jonas, it becomes clear that the community is sheltered from a true and meaningful life experience. They don't hold painful memories (as the Receiver/Giver hold those for them), but they also do not have memories of love. Families are structured based on their compatibility and everyone agrees to cooperate for the betterment of the community. When Jonas realizes how much the community could be, he really struggles with how they choose to interact with each other, devoid of all emotional connections.
The Receiver cannot die before his memories are transferred to the next Receiver-in-Training (which is a highly selective process) because all the memories that the Receiver holds would be released to the community. Not only would they then know of love, but they would also know of hate and sorrow. The community members have no understanding of these feelings, and it would lead to massive confusion as they all tried to simultaneously process these previously unknown emotions. Nevertheless, Jonas continues pondering the idea of somehow releasing the memories to his community because, as he tells Gabriel, "There could be love" (Chapter 16). This idea continues to gain momentum in his thoughts as the novel nears its end.

In the unfortunate event that Jonas should fall into the river and drown, the community would be able to access the difficult memories Jonas received from the Giver during his training, and chaos would ensue. The Giver explains to Jonas that the community suffered greatly when the previous Receiver of Memory requested release, which is why Jonas is not allowed to request to be released. According to the Giver, when the previous Receiver of Memory requested release, her memories drifted into the atmosphere, where the community had access to them. The painful, difficult memories caused chaos and panic throughout the community because the citizens could not handle the traumatic memories. In Jonas's community, comfort and safety are paramount, and citizens are not exposed to the difficult memories and experiences that Jonas and the Giver understand. Since being released is simply a euphemism for dying, the community would suffer from Jonas's loose memories the same way they suffered when the previous Receiver of Memory was released.