Define Flood Stages

A flood can be damaging to human life, property and lands surrounding a river or lake in a flood stage. When a flood stage is declared, a river or other body of water has reached a point at which the water is overflowing the banks and posing a risk to safety and mobility in the affected areas.

Stages

• Stages in water level are recorded water levels in comparison to some other piece of information, such as sea level. The stages of a body of water rise in a nonlinear fashion as the volume of water that crosses through any specific point of the water body increases.

Flood Stages

• A flood stage is defined as a rise in the stages of water levels sufficient to cause overbank flowing with the potential to damage properties, cover roads and completely flood lower land. A flood stage is not the same as a general overbank flow, in which the water level tops the channel and impacts the way the channels surrounding the water body are shaped.

Area Impacted

• Floods are not only determined by the stage or the crest of the water, but also by topography. The areas most affected by a flood depend on the slope of the land near the body of water. An area with low slopes and flat topography will be affected more than an area with steep slopes and hilly topography. It is because of this that levees are often created in areas where a river or lake has a low riverbank to steepen the slope and prevent flooding.

Forecasting Floods

• A flood may be forecast by taking history of floods in the area and recurrence intervals in the affected area into account. These calculations and predictions often require complex graphic systems and analysis of the annual maximum discharge of water in the area to calculate the recurrence interval.