Rill
Encyclopedia
A Rill can be a:
geomorphology
, a rill is a narrow and shallow incision into topsoil layers, resulting from erosion
by overland flow or surface runoff
. Rills are most common on slopes of unvegetated ground and agricultural land. However, they can occur on a variety of surfaces. Rills may even be found on the surface of certain soluble rocks like limestone. Rills are often seen as the first signs of major soil erosion, and if left to grow, may evolve into larger fluvial features like gullies, streams, or rivers.
Formation of Rills
Rills are created when water erodes the topsoil on hillsides, and so, are significantly affected by seasonal weather patterns. They tend to appear more often in rainier months. Rills begin to form when the runoff shear stress, the ability of surface runoff to detach soil particles, overcomes the soil’s shear strength, the ability of soil to resist force working parallel to the soil’s surface. This begins the erosion process as water breaks soil particles free and carries them down the slope. These forces explain why sandy, loamy soils are especially susceptible to the formation of rills, whereas dense clays tend to resist rill formation.
Rills cannot form on every surface, and their formation is intrinsically connected to the steepness of the hillside slope. Gravity determines the force of the water, which provides the power required to start the erosional environment necessary to create rills. Therefore, the formation of rills is primarily controlled by the slope of the hillside. Slope controls the depth of the rills, while the length of the slope and the soil’s permeability control the number of incisions in an area. Each type of soil has a threshold value, a slope angle below which water velocity cannot produce sufficient force to dislodge enough soil particles for rills to form. For instance, on many non-cohesive slopes, this threshold value hovers around an angle of 2 degrees with a shear velocity
between 3 and 3.5 cm/s.
After rills begin forming, they are subjected to variety of other erosional forces which may increase their size and output volume. Up to 37% of erosion in a rill-ridden area may derive from mass movement, or collapse, of rill sidewalls. As water flows through a rill, it will undercut into the walls, triggering collapse. Also, as water seeps into the soil of the walls, they weaken, amplifying the chance of wall collapse. The erosion created by these forces increases the size of the rill while also swelling its output volume.
Significance of Rill Erosion
Although rills are small, they transport significant amounts of soil each year. Some estimates claim rill flow has a carrying capacity of nearly ten times that of non-rill, or interrill, areas. In a moderate rainfall, rill flow can carry rock fragments up to 9 cm in diameter downslope. In 1987, scientist J. Poesen conducted an experiment on the Huldenberg field in Belgium which revealed that during a moderate rainfall, rill erosion removed as much as much as 200 kg (in submerged weight) of rock.
Unfortunately, the considerable effect rills have on landscapes often negatively impact human activity. Rills have been observed washing away archaeological sites. They are also very common in agricultural areas because sustained agriculture depletes the soil of much of its organic content, increasing the erodibility of the soil. Agricultural machines, such as tractors, compact the soil to the point where water flows over the surface rather than seeping into the soil. Tractor wheel impressions often channel water, providing a perfect environment for the generation of rills. If left alone, these rills may erode considerable amounts of arable soil.
Luckily, rills are small and are easily repaired by tilling the soil. This will prevent, for a time at least, the rills from growing and eroding the landscape more rapidly with time.
; of stone
, brick
, concrete
, or other lining material; usually rectilinear
in cross section
; for water transportation
from a source such as a river
-creek
, spring
, reservoir
, qanat
, or aqueduct
; for domestic
consumption or agricultural
irrigation
of crop land
uses.
Rills were traditionally used in Middle East
ern and Mediterranean climate
cultures of ancient and historical eras; and other climates and continents worldwide. They are distinguished from a 'water ditch
' by being lined to reduce absorption losses and to increase durability. The Falaj irrigation system at the Al Ain
Oasis
, in present day Abu Dhabi Emirate
, uses rills as part of its qanat
water system. Sometimes in the Spanish language
they are called Acequia
s.
s, and often tile
d and part of a fountain
design.
The historical origins are from paradise garden
religious images that first translated into ancient Persian Gardens
. Rills were later exceptionally developed in the Moorish
(Spanish) Gardens
of Al-andalus
, such as at the Alhambra
in Granada
; and also in other Islam
ic gardens, cultures, and countries. Early 20th century examples are in the Maria Louisa Park
gardens in Seville
, Spain
; and at the Casa del Herrero
gardens in Montecito, California
.
form for playback.
- 1.) natural fluvialFluvialFluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
topographic feature; - 2.) functional constructed channelChannel (geography)In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks.A channel is also the natural or human-made deeper course through a reef, sand bar, bay, or any shallow body of water...
to carry a water supplyWater supplyWater supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...
from a water source some distance away; - 3.) aesthetic gardenGardenA garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form today is known as a residential garden, but the term garden has...
water featureWater featureIn landscape architecture and garden design, a water feature is one or more items from a range of fountains, pools, ponds, cascades, waterfalls, and streams. Before the 18th century they were usually powered by gravity, though the famous Hanging Gardens of Babylon are described by Strabo as...
.
Natural
In fluvialFluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
, a rill is a narrow and shallow incision into topsoil layers, resulting from erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
by overland flow or surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
. Rills are most common on slopes of unvegetated ground and agricultural land. However, they can occur on a variety of surfaces. Rills may even be found on the surface of certain soluble rocks like limestone. Rills are often seen as the first signs of major soil erosion, and if left to grow, may evolve into larger fluvial features like gullies, streams, or rivers.
Formation of Rills
Rills are created when water erodes the topsoil on hillsides, and so, are significantly affected by seasonal weather patterns. They tend to appear more often in rainier months. Rills begin to form when the runoff shear stress, the ability of surface runoff to detach soil particles, overcomes the soil’s shear strength, the ability of soil to resist force working parallel to the soil’s surface. This begins the erosion process as water breaks soil particles free and carries them down the slope. These forces explain why sandy, loamy soils are especially susceptible to the formation of rills, whereas dense clays tend to resist rill formation.
Rills cannot form on every surface, and their formation is intrinsically connected to the steepness of the hillside slope. Gravity determines the force of the water, which provides the power required to start the erosional environment necessary to create rills. Therefore, the formation of rills is primarily controlled by the slope of the hillside. Slope controls the depth of the rills, while the length of the slope and the soil’s permeability control the number of incisions in an area. Each type of soil has a threshold value, a slope angle below which water velocity cannot produce sufficient force to dislodge enough soil particles for rills to form. For instance, on many non-cohesive slopes, this threshold value hovers around an angle of 2 degrees with a shear velocity
Shear velocity
Shear velocity, also called friction velocity, is a form by which a shear stress may be re-written in units of velocity. It is useful as a method in fluid mechanics to compare true velocities, such as the velocity of a flow in a stream, to a velocity that relates shear between layers of flow.Shear...
between 3 and 3.5 cm/s.
After rills begin forming, they are subjected to variety of other erosional forces which may increase their size and output volume. Up to 37% of erosion in a rill-ridden area may derive from mass movement, or collapse, of rill sidewalls. As water flows through a rill, it will undercut into the walls, triggering collapse. Also, as water seeps into the soil of the walls, they weaken, amplifying the chance of wall collapse. The erosion created by these forces increases the size of the rill while also swelling its output volume.
Significance of Rill Erosion
Although rills are small, they transport significant amounts of soil each year. Some estimates claim rill flow has a carrying capacity of nearly ten times that of non-rill, or interrill, areas. In a moderate rainfall, rill flow can carry rock fragments up to 9 cm in diameter downslope. In 1987, scientist J. Poesen conducted an experiment on the Huldenberg field in Belgium which revealed that during a moderate rainfall, rill erosion removed as much as much as 200 kg (in submerged weight) of rock.
Unfortunately, the considerable effect rills have on landscapes often negatively impact human activity. Rills have been observed washing away archaeological sites. They are also very common in agricultural areas because sustained agriculture depletes the soil of much of its organic content, increasing the erodibility of the soil. Agricultural machines, such as tractors, compact the soil to the point where water flows over the surface rather than seeping into the soil. Tractor wheel impressions often channel water, providing a perfect environment for the generation of rills. If left alone, these rills may erode considerable amounts of arable soil.
Luckily, rills are small and are easily repaired by tilling the soil. This will prevent, for a time at least, the rills from growing and eroding the landscape more rapidly with time.
Functional
A constructed functional rill is a small canalCanal
Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...
; of stone
STONe
is a Japanese manga written and illustrated by Sin-Ichi Hiromoto. Kodansha released the two bound volumes of the manga on April 23, 2002 and August 23, 2002, respectively.The manga is licensed for an English-languague released in North America be Tokyopop...
, brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
, or other lining material; usually rectilinear
Rectilinear
Rectilinear may refer to:* Rectilinear grid, a tessellation of the Euclidean plane* Rectilinear lens, a photographic lens* Rectilinear locomotion, a form of animal locomotion* Rectilinear polygon, a polygon whose edges meet at right angles...
in cross section
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...
; for water transportation
Water transportation
Water transportation is the intentional movement of water over large distances. Methods of transportation fall into three categories:* Aqueducts, which include pipelines, canals, and tunnels,...
from a source such as a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
-creek
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
, spring
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...
, reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
, qanat
Qanat
A qanāt is a water management system used to provide a reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates...
, or aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....
; for domestic
Domestic market
A domestic market is a financial market. Its trades are aimed toward a single market. A domestic market is also referred to as domestic trading...
consumption or agricultural
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
of crop land
Arable land
In geography and agriculture, arable land is land that can be used for growing crops. It includes all land under temporary crops , temporary meadows for mowing or pasture, land under market and kitchen gardens and land temporarily fallow...
uses.
Rills were traditionally used in Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
ern and Mediterranean climate
Mediterranean climate
A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin, and is a particular variety of subtropical climate...
cultures of ancient and historical eras; and other climates and continents worldwide. They are distinguished from a 'water ditch
Ditch
A ditch is usually defined as a small to moderate depression created to channel water.In Anglo-Saxon, the word dïc already existed and was pronounced 'deek' in northern England and 'deetch' in the south. The origins of the word lie in digging a trench and forming the upcast soil into a bank...
' by being lined to reduce absorption losses and to increase durability. The Falaj irrigation system at the Al Ain
Al Ain
Al Ain |Spring]]), also known as the Garden City due to its greenery, is the second largest city in the Emirate of Abu Dhabi and the fourth largest city in the United Arab Emirates. With a population of 374,000 , it is located approximately 160 km east of the capital Abu Dhabi and about...
Oasis
Oasis
In geography, an oasis or cienega is an isolated area of vegetation in a desert, typically surrounding a spring or similar water source...
, in present day Abu Dhabi Emirate
Abu Dhabi (emirate)
Abu Dhabi, officially the Emirate of Abu Dhabi, , is one of seven emirates that constitute the United Arab Emirates . It is the capital of UAE and is the largest emirate by area , and second-largest by population , accounting for approximately 86% of the total land area of the UAE...
, uses rills as part of its qanat
Qanat
A qanāt is a water management system used to provide a reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates...
water system. Sometimes in the Spanish language
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
they are called Acequia
Acequia
An acequia or séquia is a community-operated waterway used in Spain and former Spanish colonies in the Americas for irrigation. Particularly in Spain, the Andes, northern Mexico, and the modern-day American Southwest, acequias are usually historically engineered canals that carry snow runoff or...
s.
Aesthetic
A Rill may also refer to narrow channels of water inset into the pavement of a garden, as linear water featureWater feature
In landscape architecture and garden design, a water feature is one or more items from a range of fountains, pools, ponds, cascades, waterfalls, and streams. Before the 18th century they were usually powered by gravity, though the famous Hanging Gardens of Babylon are described by Strabo as...
s, and often tile
Tile
A tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, or even glass. Tiles are generally used for covering roofs, floors, walls, showers, or other objects such as tabletops...
d and part of a fountain
Fountain
A fountain is a piece of architecture which pours water into a basin or jets it into the air either to supply drinking water or for decorative or dramatic effect....
design.
The historical origins are from paradise garden
Paradise garden
The Paradise garden is a form of garden, originally just paradise, a word derived from the Median language, or Old Persian. Its original meaning was "a walled-in compound or garden"; from pairi and daeza or diz...
religious images that first translated into ancient Persian Gardens
Persian Gardens
The tradition and style in the garden design of Persian gardens has influenced the design of gardens from Andalusia to India and beyond. The gardens of the Alhambra show the influence of Persian Garden philosophy and style in a Moorish Palace scale from the era of Al-Andalus in Spain...
. Rills were later exceptionally developed in the Moorish
Moorish architecture
Moorish architecture is the western term used to describe the articulated Berber-Islamic architecture of North Africa and Al-Andalus.-Characteristic elements:...
(Spanish) Gardens
Spanish garden
A traditional Spanish Garden is a style of garden or designed landscape developed in historic Spain, incorporating principles and elements of garden design from precedents in ancient Persian gardens and Islamic gardens, and the great Moorish gardens of the Al-Andalus era on the Iberian Peninsula...
of Al-andalus
Al-Andalus
Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...
, such as at the Alhambra
Alhambra
The Alhambra , the complete form of which was Calat Alhambra , is a palace and fortress complex located in the Granada, Andalusia, Spain...
in Granada
Granada
Granada is a city and the capital of the province of Granada, in the autonomous community of Andalusia, Spain. Granada is located at the foot of the Sierra Nevada mountains, at the confluence of three rivers, the Beiro, the Darro and the Genil. It sits at an elevation of 738 metres above sea...
; and also in other Islam
Islam
Islam . The most common are and . : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...
ic gardens, cultures, and countries. Early 20th century examples are in the Maria Louisa Park
Plaza de España (Seville)
The Plaza de España is a plaza located in the Parque de María Luisa , in Seville, Spain built in 1928 for the Ibero-American Exposition of 1929...
gardens in Seville
Seville
Seville is the artistic, historic, cultural, and financial capital of southern Spain. It is the capital of the autonomous community of Andalusia and of the province of Seville. It is situated on the plain of the River Guadalquivir, with an average elevation of above sea level...
, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
; and at the Casa del Herrero
Casa del Herrero
Casa del Herrero is a home and gardens located in Montecito near Santa Barbara, California. It is an estate designed and constructed in the Spanish Colonial Revival Style architecture. It is listed on the National Register of Historic Places, and made a National Historic Landmark on January 16, 2009...
gardens in Montecito, California
Montecito, California
Montecito is an unincorporated community in Santa Barbara County, California. As a census-designated place, it had a population of 8,965 in 2010. This does not include areas such as Coast Village Road, that, while usually considered part of Montecito, are actually within the city limits of Santa...
.
Other
A rill may also refer to the groove in a vinyl record where the information is stored in analogAnalog recording
Analog recording is a technique used for the recording of analog signals which among many possibilities include audio frequency, analog audio and analog video information for later playback.Analog recording methods store signals as a continual wave in or on the media...
form for playback.