The distribution of volcanic and volcaniclastic deposits in both space and time gives important clues to their origins. Distance from volcanic source, depositional setting, and stratigraphic associations are important spatial characteristics. Timing of volcanic flows with respect to associated eruptions, as well as timing of flows with respect to each other, provide additional insight into emplacement processes. Magnitudes of lahars and volcanic water floods are highly influenced by size and type of associated eruptions, which affect the extent, severity, and character of landscape disturbance, including the particle size, bulk volume, and spatial distribution of fresh primary deposits. Magnitudes of volcanic debris avalanches, which may or may not be triggered by eruptions, are highly influenced by height and volume of source volcanic edifices, by the tectonic setting and strength of a source edifice’s foundation, and by the structural integrity of source edifices themselves, which can be greatly reduced by hydrothermal alteration of the constituent rock. All three types of volcanic wet flows are capable of mobilizing sediment in volcanic drainage basins at volumes per unit drainage area and per unit time far in excess of volumes of sediment mobilized by most nonvolcanic processes.