Side valleys and tributary valleys are

valleys 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 ove ...

whose

brooks Brooks may refer to: Places ;Antarctica *Cape Brooks ;Canada *Brooks, Alberta ;United States * Brooks, Alabama * Brooks, Arkansas *Brooks, California *Brooks, Georgia * Brooks, Iowa * Brooks, Kentucky * Brooks, Maine * Brooks Township, Michigan ...

or rivers flow into greater ones. Upstream, the valleys can be classified in an increasing order which is equivalent to the usual

orographic order Orography is the study of the topographic relief of mountains, and can more broadly include hills, and any part of a region's elevated terrain. Orography (also known as ''oreography'', ''orology'' or ''oreology'') falls within the broader discipl ...

: the tributaries are ordered from those nearest to the source of the river to those nearest to the mouth of the river. A

confluence In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); o ...

is where two or more tributaries or rivers flow together.

Orographic order (e.g. Humber)

In the orographic classification (order of rivers) the

tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage ...

river has order ''n+1'', if ''n'' describes the primary (or main) river. A river which flows directly into the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

(e.g. the English rivers

Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the R ...

Humber The Humber is a large tidal estuary on the east coast of Northern England. It is formed at Trent Falls, Faxfleet, by the confluence of the tidal rivers Ouse and Trent. From there to the North Sea, it forms part of the boundary between t ...

) has the orographic order n=1, the River Ouse n=2, the Wharfe n=3 and so on.

Geomorphology

The term "side valley" is used for ''higher order valleys'' near mountains (example above: the Pennines), as opposed to lower valleys that do not have a strong relief. This is because the " main stem river" (into which the secondary river flows) passes much more water than its tributaries and therefore * has a lower current. * has finer

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

s that are deposited in a more flat manner. The higher the order of a valley, the steeper the

hill A hill is a landform that extends above the surrounding terrain. It often has a distinct summit. Terminology The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally considered to be not a ...

sides. Looking upstream, the steepest slopes are normally near the source of a brook (with the exception of very hard rocks in downstream direction).

Hanging valleys

The

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

of broad rivers lies in flat regions (river flats) rather than in regions with higher elevation. Therefore, the

stream gradient Stream gradient (or stream slope) is the grade (slope), grade (or slope) of a stream measured by the ratio of drop in elevation per unit horizontal distance, usually expressed as metre, meters per kilometre, kilometer or Foot (length), feet per mile ...

of the tributary near its mouth is small (e.g. 1 m per km), but much more at waters of higher order (in the

Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...

up to 100 m per km). This is one reason for the large number of

hanging 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 ...

s in some mountain ranges (e.g.

Salzburg Salzburg (, ; literally "Salt-Castle"; bar, Soizbuag, label=Bavarian language, Austro-Bavarian) is the List of cities and towns in Austria, fourth-largest city in Austria. In 2020, it had a population of 156,872. The town is on the site of the ...

or Graubünden). Glaciologic or geologic reasons: * The

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

s of the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

caused major

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

that resulted in many

U-shaped Many shapes have metaphorical names, i.e., their names are metaphors: these shapes are named after a most common object that has it. For example, "U-shape" is a shape that resembles the letter U, a bell-shaped curve has the shape of the vertical ...

"glacial valleys", especially at an altitude of 400–800 m which is typical for alpine main valleys. * A

valley shoulder 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 ...

appears at the place where the tributary flowed into the river before the glacial period. The side valley loses its height and develops into a hanging valley. * In permeable rock like

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

) a side-valley becomes a

gorge A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tenden ...

. * In

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

or other crystalline areas a

waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in several wa ...

may result. These stages of valley genesis can be seen in higher mountain ranges - e.g. in the "young"

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

, in the "old" ranges and

fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Förden and East Jutland Fjorde, Germany, ...

s of

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...

, or in the Eastern Alps (

Salzach The Salzach (Austrian: �saltsax ) is a river in Austria and Germany. It is in length and is a right tributary of the Inn, which eventually joins the Danube. Its drainage basin of comprises large parts of the Northern Limestone and Central E ...

Inn Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

valley).

Sandbanks Sandbanks is an affluent neighbourhood of Poole, Dorset, on the south coast of England, situated on a narrow spit of around 1 km2 or 0.39 sq mi extending into the mouth of Poole Harbour. It is known for its high property prices and for it ...

often occur at reaches with slow current, especially near river banks. Studying the various

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

rock types is an excellent and cheap

survey Survey may refer to: Statistics and human research * Statistical survey, a method for collecting quantitative information about items in a population * Survey (human research), including opinion polls Spatial measurement * Surveying, the techniq ...

for a summarized

geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

of the rivers watershed (catchment area). Generally the main river and tributary are easily identified, as one stream is both longer and carries more water than the other. Occasionally one stream is longer, but the other carries more water. This case offers no fixed rules, but the longer valley is usually chosen as the main valley. In

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

the long Alpine

Rhine ), Surselva, Graubünden, Switzerland , source1_coordinates= , source1_elevation = , source2 = Rein Posteriur/Hinterrhein , source2_location = Paradies Glacier, Graubünden, Switzerland , source2_coordinates= , so ...

is chosen as the main stream, although the Aar carries more water. The

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it f ...

carries more water while the Missouri River is much longer, but is still rated the tributary.

Shape

Whereas the valleys near river flats don't have special forms, the shape of alpine valleys depends much more from the former glaciology and of the rock type. Side- or secondary valleys can be V-shaped or U-shaped.

Valley floor 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 ove ...

s vary - from just a few meters up to some 100 m (e.g.

Bad Gastein Bad Gastein (; formerly ''Badgastein''; Southern Bavarian: ''Bod Goschdei'') is a spa town in the district of St. Johann im Pongau, in the Austrian state of Salzburg. Picturesquely situated in a high valley of the Hohe Tauern mountain range, it ...

or St. Moritz, where small towns have been developed instead of 1000 or 1500 m altitude). Some valleys are stepped in longitudinal direction (German "Talstufe") which means that these zones show a quicker

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

than average. The brook digs its own canal and the eroded sediments are deposed at the end of each clammy, forming a series of local

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

s. They are an excellent sites for alpine

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or sw ...

References

{{DEFAULTSORT:Side Valley Valleys Hydrography Hydrology Geography terminology