'A “hundred-year flood” sounds like a factor of time, as if the land were expected to flood only once every 100 years, but what it’s really meant to express is risk — the land has a 1 percent chance of flooding each year. As waters rise, though, flooding in low-lying places without sea walls will become more and more common until the presence of water is less about chance and more about certainty. And few insurers are willing to bet against a certainty. Critics argue that safer building practices created a perverse incentive — to build, and to stay, in flood-prone areas by bailing people out repeatedly and by spreading, and in that way hiding, the true costs of risk leaving the government on the hook for disaster assistance after floods. “Constant risk — that’s not what insurance is about.” As climate insecurity mounts, the math will get harder.'