Flood stage is a term used in weather and hydrology to describe the level of water in a river or a lake that causes flooding of the surrounding areas. Flood stage is measured by a device called a stream gauge or a tide gauge, which records the height of the water surface. When the water level exceeds the flood stage, it can pose a risk to lives, property, or commerce, and trigger flood warnings or advisories. Flood stage varies depending on the location and the characteristics of the water body and the land. It is not necessarily the same as bankfull stage, which is the level at which the water fills the channel of the river or lake.