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Stream gradient is the
grade Grade or grading may refer to: Arts and entertainment * Grade (band) Grade is a melodic hardcore band from Canada, often credited as pioneers in blending metallic hardcore with the hon and melody of emo, and - most notably - the alternating scr ...
measured by the ratio of drop in elevation of a
stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the No ...

stream
per unit horizontal distance, usually expressed as
meter The metre ( Commonwealth spelling) or meter (American spelling Despite the various English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English ...
s per
kilometer The kilometre (SI symbol: km; or ), spelt kilometer in American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the Eng ...
or
feet The foot (plural: feet) is an anatomical Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemist ...
per
mile The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and US customary unit United States customary units (U.S. customary units) are a system of measurements commonly u ...
.


Hydrology and geology

A high gradient indicates a steep slope and rapid
flow Flow may refer to: Science and technology * Flow (fluid) or fluid dynamics, the motion of a gas or liquid * Flow (geomorphology), a type of mass wasting or slope movement in geomorphology * Flow (mathematics), a group action of the real numbers on ...
of
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
(i.e. more ability to erode); where as a low gradient indicates a more nearly level
stream bed A stream bed or streambed is the channel bottom of a stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; lit ...
and sluggishly moving water, that may be able to carry only small amounts of very fine
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
. High gradient streams tend to have steep, narrow V-shaped
valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...

valley
s, and are referred to as young streams. Low gradient streams have wider and less rugged
valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...

valley
s, with a tendency for the stream to
meander A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediment Sediment is a naturally occurring material that is broken down by processes of weath ...

meander
. Many rivers involve, to some extent, a flattening of the river gradient as approach the terminus at sea level.


Fluvial erosion

A stream that flows upon a uniformly
erodible
erodible
substrate will tend to have a steep gradient near its source, and a low gradient nearing zero as it reaches its
base level In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processe ...
. Of course, a uniform substrate would be rare in nature; hard layers of
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
along the way may establish a temporary base level, followed by a high gradient, or even a
waterfall A waterfall is a point in a river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its cour ...

waterfall
, as softer materials are encountered below the hard layer. Human
dam A dam is a barrier that stops or restricts the flow of surface water An example of surface water is Lake Kinney. Surface water is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tas ...

dam
s,
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...
, changes in
sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloquial, ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in th ...

sea level
, and many other factors can also change the "normal" or ''natural'' gradient pattern.


Topographic mapping

On
topographic map In modern mapping, a topographic map or topographic sheet is a type of map A map is a symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond wh ...
s, stream
gradient In vector calculus Vector calculus, or vector analysis, is concerned with differentiation Differentiation may refer to: Business * Differentiation (economics), the process of making a product different from other similar products * Prod ...
can be easily approximated if the scale of the map and the contour intervals are known.
Contour lines A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve In mathematics, a curve (also called a curved line in older texts) is an object similar to a line (geometry), line, but that does not have to be ...
form a V-shape on the map, pointing upstream. By counting the number of lines that cross a certain segment of a stream, multiplying this by the contour interval, and dividing that quantity by the length of the stream segment, one obtains an approximation to the stream gradient. Because stream gradient is customarily given in feet per 1000 feet, one should then measure the amount a stream segment rises and the length of the stream segment in feet, then multiply feet per foot gradient by 1000. For example, if one measures a scale mile along the stream length, and counts three contour lines crossed on a map with ten-foot contours, the gradient is approximately 5.7 feet per 1000 feet, a fairly steep gradient.


See also

*
Channel typesA wide variety of river and stream channel types exist in limnology, the study of inland waters. All these can be divided into two groups by using the Stream gradient, water-flow gradient as either ''low gradient channels'' for streams or rivers with ...
*
Discharge (hydrology) In hydrology Hydrology (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popu ...
*
Hydraulic gradient Fluid flows from the tank at the top to the basin at the bottom under the pressure of the hydraulic head. Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum A vertical datum, altimetric dat ...
, concept used for aquifers * Relief ratio *
Rapid Rapids are sections of a river where the river bed has a relatively steep gradient In vector calculus Vector calculus, or vector analysis, is concerned with differentiation Differentiation may refer to: Business * Differentiation (ec ...

Rapid
s *
Types of waterfall
Types of waterfall


References

Limnology
Geomorphology Geomorphology (from the Greek words ''Ge'' = earth, ''morfe'' = form and ''logos'' = study) is the science of surface features and landforms including the forces and processes that create them. Geomorphology has strong ties to geologic structure, ...
Rivers Water streams Water and the environment {{geo-term-stub