Floods are a key category of geologic processes, as presented in Part I. Examples of flood-related projects the author has worked on were presented in Part II. Part III showed that geologic paradigms can have negative effects on field work, sometimes causing evolutionists to miss or ignore evidence for relatively recent, catastrophic, regional-toglobal processes. Creationists can become so enamoured with "Flood models" that they can likewise miss evidence of small-scale, slow geologic processes (Part III). Both positions present a false dilemma since both current processes and very different past processes contributed to modern landscapes. In this paper, evidence for megafloods is presented along with peculiarities of scale, evidence for equifinality of disparate processes, and some of the limitations of extrapolating from local floods to megafloods and from regional megafloods to the Deluge. While good analogues are essential, it is also essential to recognize their limitations, especially effects of scale.