In her 40 years living by the water’s edge, Amissa Irakoze never much feared Lake Tanganyika. Floods were frequent, even lapping at her front door, but eventually they always receded. She could never have foreseen what happened in April 2020. Returning from working in the fields, Irakoze found her home in northwest Burundi was under the water and her 10 children missing. “I screamed: ‘My children, my children, my children,’” the single mother said, miming a gesture of desperation. “The children were swept away, but some people nearby who could swim used boats to fish them out and b...