Stream

A stream smaller than a creek, especially one that is fed by a spring or seep. It is usually small and easily forded. A brook is characterised by its shallowness.

A creek (/kriːk/) or crick (/krɪk/):[5][6]

• In Australia, Canada, New Zealand and the United States, a (narrow) stream that is smaller than a river; a minor tributary of a river; a brook.[12] Sometimes navigable by water craft and may be intermittent.
• In the United Kingdom, India, and parts of Maryland, New England,[13] a tidal inlet, typically in a salt marsh or mangrove swamp, or between enclosed and drained former salt marshes or swamps (e.g. Portsbridge Creek separating Portsea Island from the mainland). In these cases, the "stream" is the tidal stream, the course of the seawater through the creek channel at low and high tide.

A river is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a navigable waterway.[14]

The linear channel between the parallel ridges or bars on a shoreline beach or river floodplain, or between a bar and the shore. Also called a swale.

A tributary is a contributory stream to a larger stream, or a stream which does not reach a static body of water such as a lake, bay or ocean[15] but joins another river (a parent river). Sometimes also called a branch or fork.[16]

A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel, and the phenomenon is known as river bifurcation. Distributaries are common features of river deltas, and are often found where a valleyed stream enters wide flatlands or approaches the coastal plains around a lake or an ocean. They can also occur inland, on alluvial fans, or where a tributary stream bifurcates as it nears its confluence with a larger stream. Common terms for individual river distributaries in English-speaking countries are arm and channel.

• Branch is used to name streams in Maryland and Virginia.[17]
• Creek is common throughout the United States, as well as Australia.
• Falls is also used to name streams in Maryland, for streams/rivers which have waterfalls on them, even if such falls only have a small vertical drop. Little Gunpowder Falls and the Jones Falls are actually rivers named in this manner, unique to Maryland.
• Kill in New York, Pennsylvania, Delaware, and New Jersey comes from a Dutch language word meaning "riverbed" or "water channel", and can also be used for the UK meaning of 'creek'.
• Run in Ohio, Maryland, Michigan, New Jersey, Pennsylvania, Virginia, or West Virginia can be the name of a stream.[18]
• Run in Florida is the name given to streams coming out of small natural springs.[19] River is used for streams from larger springs like the Silver River and Rainbow River.
• Stream and brook are used in Midwestern states, Mid-Atlantic states, and New England.[18]

• Allt is used in the Scottish Highlands.
• Beck is used in Lincolnshire to Cumbria in areas which were once occupied by the Danes and Norwegians.[20]
• Bourne or winterbourne is used in the chalk downland of southern England for ephemeral rivers.[21] When permanent, they are chalk streams.
• Brook.[22]
• Burn is used in Scotland and North East England.[23]
• Gill or ghyll is seen in the north of England and Kent and Surrey influenced by Old Norse. The variant "ghyll" is used in the Lake District and appears to have been an invention of William Wordsworth.[24]
• Nant is used in Wales.[25]
• Rivulet is a term encountered in Victorian era publications.[26]
• Stream
• Syke is used in the Scottish Lowlands and Cumbria for a seasonal stream.[27]

To qualify as a stream, a body of water must be either recurring or perennial. Recurring (intermittent) streams have water in the channel for at least part of the year. A stream of the first order is a stream which does not have any other recurring or perennial stream feeding into it. When two first-order streams come together, they form a second-order stream. When two second-order streams come together, they form a third-order stream. Streams of lower order joining a higher order stream do not change the order of the higher stream.

The gradient of a stream is a critical factor in determining its character and is entirely determined by its base level of erosion. The base level of erosion is the point at which the stream either enters the ocean, a lake or pond, or enters a stretch in which it has a much lower gradient, and may be specifically applied to any particular stretch of a stream.

In geological terms, the stream will erode down through its bed to achieve the base level of erosion throughout its course. If this base level is low, then the stream will rapidly cut through underlying strata and have a steep gradient, and if the base level is relatively high, then the stream will form a flood plain and meander.

Meanders are looping changes of direction of a stream caused by the erosion and deposition of bank materials. These are typically serpentine in form. Typically, over time the meanders gradually migrate downstream. If some resistant material slows or stops the downstream movement of a meander, a stream may erode through the neck between two legs of a meander to become temporarily straighter, leaving behind an arc-shaped body of water termed an oxbow lake or bayou. A flood may also cause a meander to be cut through in this way.

Typically, streams are said to have a particular profile, beginning with steep gradients, no flood plain, and little shifting of channels, eventually evolving into streams with low gradients, wide flood plains, and extensive meanders. The initial stage is sometimes termed a "young" or "immature" stream, and the later state a "mature" or "old" stream.

The stream load is defined as the solid matter carried by a stream. Streams can carry sediment, or alluvium. The amount of load it can carry (capacity) as well as the largest object it can carry (competence) are both dependent on the velocity of the stream.

A perennial stream is one which flows continuously all year.[39]^: 57 Some perennial streams may only have continuous flow in segments of its stream bed year round during years of normal rainfall.[40][41] Blue-line streams are perennial streams and are marked on topographic maps with a solid blue line.

Generally, streams that flow only during and immediately after precipitation are termed ephemeral. There is no clear demarcation between surface runoff and an ephemeral stream,[39]^: 58 and some ephemeral streams can be classed as intermittent—flow all but disappearing in the normal course of seasons but ample flow (backups) restoring stream presence — such circumstances are documented when stream beds have opened up a path into mines or other underground chambers.[42]

According to official U.S. definitions, the channels of intermittent streams are well-defined,[43] as opposed to ephemeral streams, which may or may not have a defined channel, and rely mainly on storm runoff, as their aquatic bed is above the water table.[44] An ephemeral stream does not have the biological, hydrological, and physical characteristics of a continuous or intermittent stream.[44] The same non-perennial channel might change characteristics from intermittent to ephemeral over its course.[44]

Australian creek, low in the dry season, carrying little water. The energetic flow of the stream had, in flood, moved finer sediment further downstream. There is a pool to lower right and a riffle to upper left of the photograph.

A small, narrow stream flowing down a tiny dell in Pennsylvania.

Washes can fill up quickly during rains, and there may be a sudden torrent of water after a thunderstorm begins upstream, such as during monsoonal conditions. In the United States, an intermittent or seasonal stream is one that only flows for part of the year and is marked on topographic maps with a line of blue dashes and dots.[39]^: 57–58 A wash, desert wash, or arroyo is normally a dry streambed in the deserts of the American Southwest, which flows after sufficient rainfall.

In Italy, an intermittent stream is termed a torrent (Italian: torrente). In full flood the stream may or may not be "torrential" in the dramatic sense of the word, but there will be one or more seasons in which the flow is reduced to a trickle or less. Typically torrents have Apennine rather than Alpine sources, and in the summer they are fed by little precipitation and no melting snow. In this case the maximum discharge will be during the spring and autumn.

An intermittent stream can also be called a winterbourne in Britain, a wadi in the Arabic-speaking world or torrente or rambla (this last one from arabic origin) in Spain and Latin America. In Australia, an intermittent stream is usually called a creek and marked on topographic maps with a solid blue line.