the risk the levees faced was twofold—the pressure of the river and the malevolence of the humans in their vicinity. The confined river put immense pressure on levees, and an at-risk town’s best defense could be to sabotage the levee on the other side of the river. Once one side failed, the pressure on the other was eased. So, in a real-life prisoner’s dilemma, a community that was threatened and had the means, the desperation, and the shamelessness could stay safe by putting its neighbors underwater.
