Drainage system (geomorphology)

Drainage system (geomorphology)

In geomorphology, a drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. Geomorphologists and hydrologists often view streams as being part of drainage basins. A drainage basin is the topographic region from which a stream receives runoff, throughflow, and groundwater flow. Drainage basins are divided from each other by topographic barriers called a watershed. A watershed represents all of the stream tributaries that flow to some location along the stream channel. The number, size, and shape of the drainage basins found in an area varies and the larger the topographic map, the more information on the drainage basin is available.[1]

Contents

Types of drainage system

Drainage systems can fall into one of several categories, depending on the topography and geology of the land:

Dendritic drainage pattern.
Parallel drainage pattern.
Trellis drainage pattern.

Dendritic drainage system

Dendritic drainage systems (from Greek δενδρίτης, dendrites, "of or pertaining to a tree") are the most common form of drainage system. In a dendritic system, there are many contributing streams (analogous to the twigs of a tree), which are then joined together into the tributaries of the main river (the branches and the trunk of the tree, respectively). They develop where the river channel follows the slope of the terrain. Dendritic systems form in V-shaped valleys; as a result, the rock types must be impervious and non-porous.[2]

Parallel drainage system

A parallel drainage system is a pattern of rivers caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. This system forms on uniformly sloping surfaces, for example, rivers flowing southeast from the Aberdare Mountains in Kenya.

Trellis drainage system

The geometry of a trellis drainage system is similar to that of a common garden trellis used to grow vines. As the river flows along a strike valley, smaller tributaries feed into it from the steep slopes on the sides of mountains. These tributaries enter the main river at approximately 90 degree angles, causing a trellis-like appearance of the drainage system. Trellis drainage is characteristic of folded mountains, such as the Appalachian Mountains in North America.[3]

Rectangular drainage system

Rectangular drainage develops on rocks that are of approximately uniform resistance to erosion, but which have two directions of jointing at approximately right angles. The joints are usually less resistant to erosion than the bulk rock so erosion tends to preferentially open the joints and streams eventually develop along the joints. The result is a stream system in which streams consist mainly of straight line segments with right angle bends, and tributaries join larger streams at right angles.[3]

Radial drainage system

In a radial drainage system the streams radiate outwards from a central high point. Volcanos usually display excellent radial drainage. Other geological features on which radial drainage commonly develops are domes and laccoliths. On these features the drainage may exhibit a combination of radial and annular patterns.[3]

Deranged drainage system

A deranged drainage system is a drainage system in drainage basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological disruption. The classic example is the Canadian Shield. During the last ice age, the topsoil was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation, and a great deal of water to collect in the low points, explaining the large number of lakes which are found in Canada. The watersheds are young and are still sorting themselves out. Eventually the system will stabilize.[1]

Annular drainage pattern

In an annular drainage pattern streams follow a roughly circular or concentric path along a belt of weak rock, resembling in plan a ringlike pattern. It is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness, as in the Red Valley, which nearly encircles the domal structure of the Black Hills of South Dakota.

Footnotes

  1. ^ a b Pidwirny, M. (2006). "The Drainage Basin Concept". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/fundamentals/10aa.html
  2. ^ Lambert, David (1998). The Field Guide to Geology. Checkmark Books. pp. 130–131. ISBN 0-8160-3823-6. 
  3. ^ a b c Ritter, Michael E. The Physical Environment: an Introduction to Physical Geography. 2006. Date visited. http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/title_page.html

External links


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Drainage system (Geomorphology) — In geomorphology, a drainage system is the pattern formed by the streams, rivers, and lakes in a particular watershed. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the… …   Wikipedia

  • Drainage system — may refer to: A drainage system (geomorphology), the pattern formed by the streams, rivers, and lakes in a particular drainage basin. A drainage system (agriculture), an intervention to control waterlogging aiming at soil improvement for… …   Wikipedia

  • Geomorphology — (from Greek: γη, ge , earth ; μορφή, morfé , form ; and λόγος, logos , knowledge ) is the study of landforms and the processes that shape them. Geomorphologists seek to understand why landscapes look the way they do: to understand landform… …   Wikipedia

  • Drainage basin — Example of a drainage basin. The dashed line is the main water divide of the hydrographic basin A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit… …   Wikipedia

  • Drainage — See also: Storm drain and Stormwater Deep inside a Sydney drain in New South Wales Drainage is the natural or artificial removal of surface and sub surface water from an area. Many agricultural soils need drainage to improv …   Wikipedia

  • Land drainage — may refer to:* surface drainage of the land related to: ** geomorphological pattern of natural drains, streams, rivers, etc. see drainage system (geomorphology) ** surface runoff of excess rainfall from the land, see surface runoff ** land… …   Wikipedia

  • Tigris-Euphrates river system — ▪ river system, Asia Introduction  great river system of Southwest Asia, comprising the Tigris and Euphrates rivers, which have their sources within 50 miles (80 km) of each other in eastern Turkey and travel southeast through northern Syria and… …   Universalium

  • List of watershed topics — This list is incomplete; you can help by expanding it. See also: Drainage system (geomorphology) This list embraces topographical watersheds and drainage basins and other topics focused on them. Contents 1 Terms different uses …   Wikipedia

  • talf —    [ geomorphology ]    A geomorphic component of flat plains (e.g., lake plain, low coastal plain, low gradient till plain) consisting of an essentially flat (e.g., 0 1 % slopes) and broad area dominated by closed depressions and a non… …   Glossary of landform and geologic terms

  • river — river1 riverless, adj. riverlike, adj. /riv euhr/, n. 1. a natural stream of water of fairly large size flowing in a definite course or channel or series of diverging and converging channels. 2. a similar stream of something other than water: a… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”