Bayous are either stagnant or slow-moving bodies of water which fill abandoned waterways. The term by itself usually refers to a very slow stream, while the term bayou lake is often used to describe lakes or ponds in similar conditions. A bayou is normally found in very flat regions, as the lack of a slope reduces the speed at which the water flows. It is usually the outflow from a nearby major waterway, such as the Mississippi river, and as such may be affected by flooding in the main waterway.
The word is used primarily in the southern United States. The term "slough" is also used to describe essentially the same geographical feature, although it tends to have a more widespread usage. The bayou is particularly associated with the Cajun culture of Louisiana, and parts of Texas and Alabama. They are also found throughout Arkansas, although most in that state use an alternate spelling of buyou.
Because of its slow-moving nature, and the relative lack of differentiation in height, a bayou often forms a sort of bog or marsh. In fact, the easiest way to think of one is simply as a stream moving through a swamp. Plants and trees may grow up through the bayou, making the water seem to flow haphazardly through the land as a whole. The ecology in these wetlands is quite diverse, and in some cases unique. The land is always damp, leading to specialized plants that do well with little or no oxygen, and which are equipped to make use of the copious water. Cattails, water lilies, bulrushes, and cedar are all examples of vegetation which does well in this environment.
Because of its often maze-like character, eternal dampness, and sometimes haunting vegetation, the bayou is often the location in fiction of frightening stories. Tales of voodoo often take place there, and a number of horror stories are set in the deep bayou, far from civilization. Alligators inhabit much of the bayou in Louisiana, adding to the mystique of fear that surrounds the region.
The city of Houston, Texas is often referred to as Bayou City. This is a reference to the many streams that make their way through the city of Houston, or just outside the city limits. The White Oak Bayou, Buffalo Bayou, and Carpenters Bayou are the most famous of these, but there are more than 18 in the region.