Sheet erosion or sheet wash is the even erosion of substrate along a wide area. It occurs in a wide range of settings such as

coastal plain A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Co ...

s, hillslopes,

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells ...

es,

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

plains and

semi-arid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-ar ...

plains. Water moving fairly uniformly with a similar thickness over a surface is called sheet flow, and is the cause of sheet erosion. Sheet erosion implies that any flow of water that causes the erosion is not canalized. If a hillslope surface contains many irregularities, sheet erosion may give way to erosion along small channels called

rill In hillslope geomorphology, a rill is a shallow channel (no more than a few inches/decimeters deep) cut into soil by the erosive action of flowing surface water. Similar but smaller incised channels are known as microrills; larger incised c ...

s, which can then converge forming

gullies 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 la ...

. However, sheet erosion may occur despite some limited unevenness in the sheet flow arising from clods of earth, rock fragments, or vegetation. Sheet erosion occurs in two steps. First, rainsplash dislodges small particles of the substrate and then the particles are carried away, usually short distances, by a thin and uniform layer of water known as sheetflow. Transport by the sheetflow is usually over small distances, meaning that sheet erosion is a low magnitude process. However, the frequency over time with which this occurs may be high, compensating for the small change observed in each individual episode of sheet erosion. A sheetflood can be distinguished from an ordinary sheetflow by its much greater magnitude and much lesser frequency. Sheetfloods have been associated by various scientists with a number of causes, including: high-intensity rain,

low relief Relief is a sculptural method in which the sculpted pieces are bonded to a solid background of the same material. The term ''relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the impression that the ...

, lack of vegetation, low permeability of the substrate, strong weather contrast between seasons, slope form and climate change. Sheetfloods are commonly turbulent while sheetflow may be laminar or turbulent. Sheet erosion is common in recently plowed fields and bare ground where the substrate, typically soil, is not consolidated. The resulting loss of material by sheet erosion may result in the destruction of valuable

topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic matte ...

s. Tough

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns and ...

, such as

vetiver ''Chrysopogon zizanioides'', commonly known as vetiver and khus, is a perennial bunchgrass of the family Poaceae. Vetiver is most closely related to ''Sorghum'' but shares many morphological characteristics with other fragrant grasses, such as ...

, hinders the development of sheet flow. The sheet erosion caused by a single rainstorm may account for the loss of up to hundred tons of small particles in an acre. It has been argued that in the late Neoproterozoic Era, sheet erosion was a dominant erosion process due to the lack of plants on land. As such, sheet erosion may have contributed to shape important landforms like the

Sub-Cambrian peneplain The sub-Cambrian peneplain is an ancient, extremely flat, erosion surface (peneplain) that has been exhumed and exposed by erosion from under Cambrian strata over large swathes of Fennoscandia. Eastward, where this peneplain dips below Cambrian an ...

that covers much of the

Baltic Shield The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean a ...

References

{{reflist Erosion

See also

References