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Headward erosion is
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 ...
at the origin of a
stream channel In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of water or of other fluids (e.g., lava), most commonly the confine of a river, river delta or strait. The word is c ...
, which causes the origin to move back away from the direction of the stream flow, lengthening the stream channel.Essentials of Geology, 3rd Ed, Stephen Marshak It can also refer to widening of a
canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to ...
by erosion along its very top edge, when sheets of water first enter the canyon from a more roughly planar surface above it, such as at
Canyonlands National Park Canyonlands National Park is an American national park located in southeastern Utah near the town of Moab. The park preserves a colorful landscape eroded into numerous canyons, mesas, and buttes by the Colorado River, the Green River, and their ...
in
Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
. When sheets of water on a roughly planar surface first enter a depression in it, this erodes the top edge of the depression. The stream is forced to grow longer at the very top of the stream, which moves its origin back, or causes the canyon formed by the stream to grow wider as the process repeats. Widening of the canyon by erosion inside the canyon, below the canyon side top edge, or origin or the stream, such as erosion caused by the streamflow inside it, is not called headward erosion. Headward erosion is a
fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviogla ...
process of
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 lengthens a
stream A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams are ...
, a
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 ...
or a
gully A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...
at its
head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may not ...
and also enlarges its
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the ...
. The stream erodes away at the rock and soil at its headwaters in the opposite direction that it flows. Once a stream has begun to cut back, the erosion is sped up by the steep gradient the water is flowing down. As water erodes a path from its headwaters to its mouth at a standing body of water, it tries to cut an ever-shallower path. This leads to increased erosion at the steepest parts, which is headward erosion. If this continues long enough, it can cause a stream to break through into a neighboring
watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins * Drainage basin, called a "watershe ...
and capture drainage that previously flowed to another stream. For example, headward erosion by the
Shenandoah River The Shenandoah River is the principal tributary of the Potomac River, long with two forks approximately long each,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed August 15, 2011 in t ...
, a
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 ...
of the
Potomac River The Potomac River () drains the Mid-Atlantic United States, flowing from the Potomac Highlands into Chesapeake Bay. It is long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map. Retrieved Augu ...
in the U.S. state of
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...
, permitted the Shenandoah to capture successively the original upstream segments of Beaverdam Creek, Gap Run and Goose Creek, three smaller tributaries of the Potomac. As each capture added to the Shenandoah's
effluent Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters either untreated or after being treated at a facility. The term has slightly different meanings in certain contexts, and may contain various polluta ...
, or discharge, it accelerated the process of headward erosion until the Shenandoah captured all drainage to the Potomac west of the
Blue Ridge Mountains The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. The mountain range is located in the Eastern United States, and extends 550 miles southwest from southern Pennsylvania through Maryland, West Virgin ...
.


Stream types created by headward erosion

Three kinds of streams are formed by headward erosion: ''insequent streams'', ''subsequent streams'', and ''obsequent and resequent streams'' (''See
Fluvial landforms of streams Fluvial processes have made streams, stream beds, and river valleys which have various classifications. Classification There are five generic classifications: *Consequent streams are streams whose course is a direct consequence of the original s ...
''.) Insequent streams form by random headward erosion, usually from sheetflow of water over the landform surface. The water collects in channels where the velocity and erosional power increase, cutting into and extending the heads of gullies. Subsequent streams form by selective headward erosion by cutting away at less resistive rocks in the terrain. Obsequent and resequent streams form after time in an area of insequent or subsequent streams. Obsequent streams are insequent streams that now flow in an opposite direction of the original drainage pattern. Resequent streams are subsequent streams that have also changed direction from their original drainage patterns.


Drainage patterns created by headward erosion

Headward erosion creates three major kinds of drainage patterns: ''
dendritic Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to: Biology *Dendrite, a branched projection of a neuron * Dendrite (non-neuronal), branching projections of certain skin cells and immune cells Physical *Dendr ...
patterns'', '' trellis patterns'', and ''rectangular and angular patterns''.
*Dendritic patterns form in homogenous landforms where the underlying bedrock has no structural control over where the water flows. They have a very characteristic pattern of branching at acute angles with no common or similarly repeating pattern. *Trellis patterns form where the underlying bedrock contains repeating weaker and stronger types of rock. The trellis pattern cuts down deeper into the weaker bedrock, and is characterized by nearly parallel streams that branch at higher angles. *Rectangular and angular patterns are characterized by branching of tributaries at nearly right angles and tributaries which themselves exhibit right-angle bends in their channels. These usually form in jointed igneous bedrocks, horizontal sedimentary beds with well-developed jointing or intersecting faults. Four minor kinds of drainage patterns also can be created: ''
radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance, a directional coordinate in a polar coordinate system * Radial set * A bearing from ...
patterns'', ''
annular Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * '' Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus c ...
patterns'',
''
centripetal A centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous ce ...
patterns'' and ''
parallel Parallel is a geometric term of location which may refer to: Computing * Parallel algorithm * Parallel computing * Parallel metaheuristic * Parallel (software), a UNIX utility for running programs in parallel * Parallel Sysplex, a cluster of IB ...
patterns''. *Radial patterns are characterized by flow of water outward from a central point, such as down a newly formed cinder volcano cone or an intrusive dome. *Annular patterns form on domes of alternating weak and hard bedrocks. The pattern formed is similar to that of a
bullseye Bullseye or Bull's Eye may refer to: Symbols * ◎ (Unicode U+25CE BULLSEYE), in the Geometric Shapes Unicode block * (Unicode U+0298 LATIN LETTER BILABIAL CLICK), the phonetic symbol for bilabial click Animals and plants * Bull's Eye, '' Eur ...
when viewed from above, as the weaker bedrocks are eroded and the harder are left in place. *Centripetal patterns form where water flows into a central location, such as in a
karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ...
limestone terrain where the water flows down into a sinkhole and then underground. *Parallel patterns are not very common and form on unidirectional regional slope or parallel landform features. They are usually limited to a small, generalized area.


See also

* Lavaka


References

{{Rivers, streams and springs Erosion Hydrology