A flood is an overflow of water that submerges or "drowns" land. The definition a flood is a covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries, or may be due to accumulation of rainwater on saturated ground in an areal flood.
When Doctor LeBon told Marvin White and Wendy Harris about his plan to bring one half of Cygnus-Uno into Earth orbit, essentially giving Earth two moons; the kids told him it was a terrible idea, because it could cause floods and avalanches. LeBon disagreed however.