In hydrology, run-on refers both to the process whereby surface runoff infiltrates the ground as it flows, and to the portion of runoff that infiltrates. Run-on is common in arid and semi-arid areas with patchy vegetation cover and short but intense thunderstorms. In these environments, surface runoff is usually generated by a failure of rainfall to infiltrate into the ground quickly enough (this runoff is termed infiltration excess overland flow). This is more likely to occur on bare soil, wit… (More on Run-on)