Slow-moving thunderstorms, or a series of storms, that move across the same area again and again are frequently the cause of the phenomenon known as ﬂash ﬂooding, and the number of deaths from ﬂash ﬂooding has exceeded deaths from tornados since 1985. Craig Childs, in Soul of Nowhere, evokes the seriousness this way: “The sound becomes familiar. Next I smell it, and that too is familiar. It is the musty scent of death, the unmistakable smell of a ﬂash ﬂood.” What happens during a ﬂash ﬂood is that too much water falls in too short a time for the terrain to absorb or safely channel it. Whether the water falls on the rocky slopes of a Colorado canyon or onto the ﬂat desert in Arizona, or whether what’s trying to hold the water back is a dam, levee, or ice jam, the abrupt and excessive combination becomes deadly. York, the only African American member of the Lewis and Clark expedition of 1804–1805, and a slave since birth, is remembered for having saved William Clark’s life when he plucked him from a ﬂash ﬂood on the Missouri River near Great Falls in present-day Montana.