Floods are a key category of geologic processes. Creationists often refer to "Flood geology," while those who try to emphasize evidence for intelligent design without any reference to the Bible often avoid geology entirely, and those with traditional old earth beliefs sometimes downplay the effects of floods. Floods observed in today’s world make important analogues to megafloods, including the Deluge of Noah’s day. This paper provides some examples of geologic work by floods and related processes in Central Montana as experienced by the author and also provides ideas about how these may apply to the study of earth history. It is important to recognize the limitations of analogues, especially effects of scale with these episodic events.—Part I introduces flood geology and provides data and interpretations related to observed floods, starting with basic open channel flow equations and principles of scour analysis. Initial scour estimates for a flood in the study area are presented. Scour analysis is complex and beset by much uncertainty, but it is still very useful since science must be constrained by real world data.