Bayous and Swamps: Where are they commonly found?

This is an interactive map of wetlands from the continental United States. It shows the locations of water bodies named Bayou, Swamp, Bog, Marsh, Slough, and Coulee. For names and types hover over the map. Zoom out to see Alaska and Hawaii. Zoom in to see all wetlands in detail.
Bayou Swamp Bog Marsh Slough Coulee


This map was inspired in my experiences as a Graduate Student in the South. I knew about the swamps in the area, but the Bayous were a completely novel term. Later I lived in Bayou City (Houston). Which highlighted the importance of the term in the South. As other wetlands, they are important features in the landscape that provide numerous beneficial services for people and for fish and wildlife" (EPA).This iconic feature of the South that has been ubiquitous in my American trips, and deserved a chart of its own. Furthermore, it needed to be visualized next to swamps, to see the pattern of their distribution.

I made this map initially with just Swamps and Bayous. After posting it on Map Porn from Reddit, I received different comments, and was suggested to use the GNIS. The initial map lacked a lot of locations. Following these suggestions I used the new data source, and was able to include other names associated to wetlands. With a bit more research I realized this map had been done before. I found that Paul Fly has a collection of maps with US Toponymy. I also found a good compilation of name maps from Roaring Brook Maps by Gregory diSanto. After checking these maps I decided I would create one that included Bayous, Swamps, Marshes, Bogs, Sloughs, and Coulees. Unlike the previous maps, this one is interactive and allows for the selection of each wetland, view their names, classification, exact location, and altitude.

The definition for Bayous from the National Geographic Encyclopedia states that "A bayou is a slow-moving creek or a swampy section of a river or a lake. They are usually found in flat areas where water collects in pools. Bayous are often associated with the southeastern part of the United States. Bayous are usually shallow and sometimes heavily wooded. They can be freshwater, saltwater, or a combination of both."

I thought Bayou was a French/Creole term. But it "originated from the Choctaw word “bayok”, which refers to a small stream. The current spelling of the word comes from the Louisiana French variation of the word “bayouque.”see Facts about Louisiana Bayous.

Bogs are mossy wetlands. Most of their water comes from rain and snow. Water in bogs is low in oxygen, very acidic and often cold. Sphagnum or peat moss is common in bots. Source: Nature Works.

"Marshes are produced by flooding, and, as a consequence, have distinctive soils, microorganisms, plants, and animals. The soils are usually anoxic or hypoxic, allowing vast numbers of microorganisms, particularly bacteria, to transform elements including nitrogen, phosphorus, and sulfur among different chemical states. Marshes are some of the most biologically productive habitats in the world, and therefore support large numbers of animals, from shrimps and fish through to birds and mammals." From: Science Direct.

A swamp is an area of land permanently saturated, or filled, with water. Many swamps are even covered by water. There are two main types of swamps: freshwater swamps and saltwater swamps. Swamps are dominated by trees. They are often named for the type of trees that grow in them, such as cypress swamps or hardwood swamps. Swamps exist in many kinds of climates and on every continent except Antarctica. From: National Geographic.

A slough is typically used to describe wetlands. Sloughs along the edges of rivers form where the old channel of the river once flowed. These areas are also referred to as oxbows because they tend to form at a bend in the old river bed, making them look like the U-shaped collar placed around the neck of an ox to which a plow is attached. Along the West Coast, sloughs are often named for the quiet, backwater parts of bays and therefore, they are part of the estuary, where freshwater flows from creeks and runoff from land mix with salty ocean water transported by the tides. Source: NOAA.

Coulees are geographical features common in southwestern parts of Canada and Northwestern regions of the United States. The word coulee is from the French-Canadian word coulee which in turn is a derivative of the French word couler which means ‘to flow.’ The name of these features is, therefore, an indication of how they form. Coulees are generally gullies or ravines, often dry ones, which were sculpted by the action of moving water. They are the products of intense erosion by water. The definitions, and as a result the features of coulees, vary from place to place. In the Great Plains, a coulee is employed interchangeably to refer to any number of water features ranging from creeks to ponds. In southern Louisiana, on the other hand, a coulee means a dry ravine or gully that becomes more sizeable as a result of rainy weather. This term has also been used to refer to small ditches and canals in swamps and perennial streams. Depending on the definition one would adopt of coulees, these geological features may be characterized by steep slopes, the vast erosive action caused by water. Most coulees today occupy ancient river beds." Source: World Atlas.


The data was downloaded from the Geographic Names Information System (GNIS), maintained by USGS. Data cleaning was done with R Project for Statistical Computing. At first I used only the data classified as Lakes. Eventually I realized that Bayous maybe classified as streams or Lakes. Therefore you will see that each name might have different classifications. I tried to leave classifications referring to water features. The Shapefiles for this map were downloaded from Natural Earth. The code was obtained and altered from Chris Williams’s Block.

Made by Luz K. Molina with D3.js.

map wetlands icluding swamps, marshes and bayous of USA