Coulee, or coulée ( or ) is a term applied rather loosely to different landforms, all of which refer to a kind of valley or drainage zone. The word ''coulee'' comes from the

Canadian French Canadian French (french: français canadien) is the French language as it is spoken in Canada. It includes Varieties of French#Canada, multiple varieties, the most prominent of which is Quebec French, Québécois (Quebec French). Formerly ''Can ...

''coulée'', from

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

''couler'' 'to flow'. The term is often used interchangeably in the

Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

for any number of water features, from ponds to

creek A creek in North America and elsewhere, such as Australia, is a stream that is usually smaller than a river. In the British Isles it is a small tidal inlet. Creek may also refer to: People * Creek people, also known as Muscogee, Native Americans ...

s. In southern Louisiana the word ''coulée'' (also spelled ''coolie'') originally meant a gully or ravine usually dry or

intermittent Intermittency is a behavior of dynamical systems: regular alternation of phases of apparently periodic and chaotic dynamics. Intermittent or intermittency may also refer to: *Intermittent river or stream, the one that ceases to flow every year or ...

but becoming sizable during rainy weather. As stream channels were dredged or canalized, the term was increasingly applied to perennial streams, generally smaller than

bayou In usage in the Southern United States, a bayou () is a body of water typically found in a flat, low-lying area. It may refer to an extremely slow-moving stream, river (often with a poorly defined shoreline), marshy lake, wetland, or creek. They ...

s. The term is also used for small ditches or canals in the swamp. In the northwestern United States, coulee is defined as a large, steep-walled, trench-like trough, which also include spillways and

flood channel Flood control channels are large and empty basins which let water flow in and out (except during flooding) or dry channels that run below the street levels of some larger cities, so that if and when a flood occurs, the water will run into these ch ...

s incised into the basalt plateau.

Types and examples

* The dry, braided channels formed by glacial drainage of the

Scablands The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods w ...

of eastern Washington, such as Grand Coulee and Moses Coulee. Moses Coulee and Lenore Canyon, lower Grand Coulee, have hanging valleys, where pre-flood tributaries enter the coulees at least above the coulee floor. * The furrowed

moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...

s channeling rain runoff in the area east of the

Missouri Coteau The Missouri Coteau, or Missouri Plateau, (french: Coteau du Missouri) is a large plateau that stretches along the eastern side of the valley of the Missouri River in central North Dakota and north-central South Dakota in the United States. In t ...

in the western United States and western Canada at the base of the Rocky Mountains. * In the western United States, tongue-like protrusions of solidified lava, forming a sort of canyon. * In Wisconsin it is applied to valleys. These valleys tend to have high, steep walls. "Hollow" is used as a synonym, often for the smallest of such valleys. The term is also applied to the greater

La Crosse, Wisconsin La Crosse is a city in the U.S. state of Wisconsin and the county seat of La Crosse County. Positioned alongside the Mississippi River, La Crosse is the largest city on Wisconsin's western border. La Crosse's population as of the 2020 census w ...

metropolitan area (i.e. the "Coulee Region"). * The Gassman Coulee in North Dakota may have been a contributing factor to the flooding of the Souris River in June 2011.

Geomorphology

Aside from those formed by volcanic eruptions, coulees are commonly canyons characterized by steep walls that have been shaped by erosion. These types of coulees are generally found in the northwestern United States and southwestern Canada. In the American west, rapid melting of glaciers at the end of the last ice age caused catastrophic flooding which removed bedrock by massive down-cutting erosion, forming deep canyons. Some coulees may be seasonally dry or contain small streams, however these small misfit streams do not have the magnitude of force necessary to form such expansive erosion. In Wisconsin, they are the product of nearly a half million years of erosion, unmodified by glaciation (see Driftless Area). The loose rocks at the base of the wall form what are called scree slopes. These are formed when chunks of the canyon wall give way in a rockslide. Left alone, the valleys are often woodland, with the ridgetops transitioning into tallgrass prairie when not turned into pasture or used for row crops. Coulees provide shelter from wind and concentrated water supplies to plants which would otherwise struggle to survive in the xeric sagebrush steppe. Trees are often found in riparian habitats along streams in coulees and at the base of their walls.Easterbrook, Don J. (1999). Surface Processes and Landforms. Prentice Hall, Upper Saddle River New Jersey. Pp. 381-385

References

{{Rivers, streams and springs Fluvial landforms Erosion landforms

Types and examples

Geomorphology

See also

References