Parts of South Sudan are on the “brink of famine” as the nation braces for a “horror scenario” ahead of the worst floods in decades, a British charity warned Wednesday. Since it gained independence in 2011, the world’s newest nation has remained plagued by instability and violence, despite rich oil reserves. South Sudan is expected to “suffer its worst floods in 60 years that will drive parts of the country to the brink of famine,” Save the Children said, citing data from the Famine Early Warning Systems Network, established by USAID. “A horror scenario is unfolding in South Sudan,” Save the C…