A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. Check dams themselves are not a type of new technology; rather, they are an ancient technique dating from the second century A.D. Check dams are typically, though not always, implemented in a system of several dams situated at regular intervals across the area of interest.
A check dam placed in the ditch, swale, or channel interrupts the flow of water and flattens the gradient of the channel, thereby reducing the velocity. In turn, this obstruction induces infiltration and reduces eroding. They can be used not only to slow flow velocity but also to distribute flows across a swale to avoid preferential paths and guide flows toward vegetation. Although some sedimentation may result behind the dam, check dams do not primarily function as sediment trapping devices.
Check dams could be designed to create small reservoirs, without possibility of silting. A self desilting design was published in Invention Intelligence, August, 1987, which while being permanent, would also remove silt as it is formed, keeping the reservoir capacity maximum. The design includes an awning, going very near the bottom level, extending to the width of the dam, and embedding into the sides. When freshets occur, the silt is automatically carried over to down stream, keeping the reservoir clear.
Check dams have traditionally been implemented in two environments: across channel bottoms and on hilly slopes. Check dams are used primarily to control water velocity, conserve soil, and improve land. They are used when other flow-control practices, such as lining the channel or creating bioswales, are impractical. Accordingly, they are commonly used in degrading temporary channels, in which permanent stabilization is impractical and infeasible in terms of resource allocation and funding due to the short life period. Or, they are used when construction delays and weather conditions prevent timely installation of other erosion control practices. This is typically seen during the construction process of large-scale permanent dams or erosion control. As such, check dams serve as temporary grade-control mechanisms along waterways until resolute stabilization is established or along permanent swales that need protection prior to installation of a non-erodible lining.
Many check dams tend to form stream pools. Under low-flow circumstances, water either infiltrates into the ground, evaporates, or seeps through or under the dam. Under high flow - flood - conditions, water flows over or through the structure. Coarse and medium-grained sediment from runoff tends to be deposited behind check dams, while finer grains flow through. Floating garbage is also trapped by check dams, increasing their effectiveness as water quality control measures.
In arid areas, check dams are often built to increase groundwater recharge in a process called managed aquifer recharge. Winter runoff thus can be stored in aquifers, from which the water can be withdrawn during the dry season for irrigation, livestock watering, and even drinking water supply. This is particularly useful for small settlements located far from a large urban center as check dams require less reliance on machinery, funding, or advanced understandings as compared to large-scale dam implementation.
As a strategy to stabilize mountain streams, the construction of check dams has a long tradition in many mountainous regions dating back to the 19th century in Europe. Because of the steep slopes in the mountain region, it may be difficult for large construction machinery to reach mountain streams; therefore, check dams have been implemented in place of large-scale dams. Because the typical high slope causes the flow velocity to move faster, a terraced system of multiple closely spaced check dams is typically necessary to reduce velocity and thereby counteract erosion. Such consolidation check dams, built in terraces, attempt to prevent both headward and downward cutting into channel beds while also stabilizing adjacent hill slopes. They are further used to mitigate flood and debris flow hazards.
Before installing a check dam, engineers inspect the site. Standard practices call for the drainage area to be ten acres or less. The waterway should be on a slope of no more than 50% and should have a minimum depth to bedrock of 2 ft. Check dams are often used in natural or constructed channels or swales. They should never be placed in live streams unless approved by appropriate local, state and/or federal authorities.
Check dams are made of a variety of materials. Because they are typically used as temporary structures, they are often made of cheap and accessible materials such as rocks, gravel, logs, hay bales, and sandbags. Of these, logs and rock check dams are usually permanent or semi-permanent; and the sandbag check dam is implemented primarily for temporary purposes. Also, there are check dams that are constructed with rockfill or wooden boards. These dams are usually implemented only in small, open channels that drain 10 acres (0.04 km2) or less; and usually do not exceed 2 ft (0.61 m) high. Woven-wire can be used to construct check dams in order to hold fine material in a gully. They are typically utilized in environments where the gully has a moderate slope (less than 10%), small drainage area, and in regions where flood flows do not typically carry large rocks or boulders. In nearly all instances, erosion control blankets, which are biodegradable open-weave blankets, are used in conjunction with check dams. These blankets help enforce vegetation growth on the slopes, shorelines and ditch bottoms.
Check dams are usually less than 2 ft (0.61 m) to 3 ft (0.91 m) high. and the center of the dam should be at least 6 in (0.15 m) lower than its edges. This criteria induces a weir effect, resulting in increased water surface level upstream for some, if not all flow conditions.
In order to effectively slow water velocity to reduce erosion and to protect the channel between dams in a larger system, the spacing must be designed properly. The check dams should be spaced such that the toe of the upstream check dam is equal to the elevation of the downstream check dam's crest. By doing so, the water can pond between check dams and thus slow the flow's velocity down substantially as the water progresses downslope.
Check dams are a highly effective practice to reduce flow velocities in channels and waterways. In contrast to big dams, check dams are implemented faster, are cost effective, and are smaller in scope. Because of this, their implementation does not typically displace people and communities nor do they destroy natural resources if designed correctly. Moreover, the dams are simple to construct and do not rely on advanced technologies – thereby they can be applied in more rural and less advanced communities, as they have been in India's drylands for some time now.
Check dams still require maintenance and sediment removal practices. They become more difficult to implement on steep slopes, as velocity is higher and the distance between dams must be shortened. Check dams, depending on the material used, can have a limited life span but if implemented correctly can be considered permanent though not encouraged.
Check dams require regular maintenance as they are used primarily as a temporary structure and thereby are not designed to withstand long-term use. Dams should be inspected every week that it is sited in the channel and after every large storm. It is important that rubble, litter, and leaves are removed from the upstream side of the dam. This is typically done when the sediment has reached a height of one-half the original height of the dam.
Further, maintenance is required when removing the check dam altogether. In order to ensure the future flow is not adversely altered, the check dam must be fully removed, including any parts that may have been dislodged and washed downstream or any newly developed bare spots where the check dam once was situated.
Amekawa Dam (Japanese: 雨川ダム) is a check dam on Ame river in Saku, Nagano Prefecture, Japan. The primary purpose is reducing water flow velocity to counteract erosion. It is also used for water supply.
The pole of inaccessibility of Japan lies near this dam.Arakawa River (Fukushima)
The Arakawa River (荒川, Arakawa) is a river in Fukushima, Fukushima, Japan.Arroyito Dam
The Arroyito Dam (in Spanish, Embalse de Arroyito) is the fifth of five dams on the Limay River in northwestern Argentine Patagonia (the Comahue region), at 315 metres (1,033 ft) above mean sea level. It was inaugurated in 1979.
The dam is made of compacted loose materials. It has a volume of 4 million cubic metres (140×10^6 cu ft), measuring 37 metres (121 ft) in height and 3,500 metres (11,500 ft) in length. It is used primarily for the generation of hydroelectricity, with an installed power of 127.8 megawatts (171,400 hp). It generates on average 560 gigawatt-hours (2,000 TJ) per year. It also serves as a check dam for El Chocón, located upstream.
The reservoir has an area of 38.6 square kilometres (14.9 sq mi) and a volume of 300 million cubic metres (11×10^9 cu ft). Its depth is 7.7 metres (25 ft) on average (maximum: 15 metres (49 ft)).Celt (tool)
In archaeology, a celt is a long, thin, prehistoric, stone or bronze tool similar to an adze, a hoe or axe-like tool.Cumberland point
A Cumberland point is a lithic projectile point, attached to a spear and used as a hunting tool. These sturdy points were intended for use as thrusting weapons and employed by various mid-Paleo-Indians (c. 11,000 BP) in the Southeastern US in the killing of large game mammals.Dam
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. The earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC.
The word dam can be traced back to Middle English, and before that, from Middle Dutch, as seen in the names of many old cities. The first known appearance of dam occurs in 1165. However, there is one village, Obdam, that is already mentioned in 1120. The word seems to be related to the Greek word taphos, meaning "grave" or "grave hill". So the word should be understood as "dike from dug out earth". The names of more than 40 places (with minor changes) from the Middle Dutch era (1150–1500 CE) such as Amsterdam (founded as 'Amstelredam' in the late 12th century) and Rotterdam, also bear testimony to the use of the word in Middle Dutch at that time.Grattoir de côté
A Grattoir de côté (translates from French as Side Scraper) is an archaeological term for a ridged variety of steep-scrapers distinguished by a working edge on one side. They were found at various archaeological sites in Lebanon including Ain Cheikh and Jdeideh II and are suggested to date to Upper Paleolithic stages three or four (Antelian).Grinding slab
In archaeology, a grinding slab is a ground stone artifact generally used to grind plant materials into usable size, though some slabs were used to shape other ground stone artifacts. Some grinding stones are portable; others are not and, in fact, may be part of a stone outcropping.
Grinding slabs used for plant processing typically acted as a coarse surface against which plant materials were ground using a portable hand stone, or mano ("hand" in Spanish). Variant grinding slabs are referred to as metates or querns, and have a ground-out bowl. Like all ground stone artifacts, grinding slabs are made of large-grained materials such as granite, basalt, or similar tool stones.Kosasthalaiyar River
Kosasthalaiyar River, also known as Kortalaiyar, is one of the three rivers that flow in the Chennai metropolitan area.Lapasari
Lapasari Village is near Rajkot city in Rajkot district in Gujarat State in India.Muthur
Muthur Tamil: முத்தூர் is a panchayat town in Kangeyam taluk in Tirupur district, Tamil Nadu, India.Nagashima Dam
The Nagashima Dam (長島ダム, Nagashima damu) is a dam on the Ōi River, located in Kawanehon Town, Haibara District, Shizuoka Prefecture on the island of Honshū, Japan.Onakkoor
Onakkoor is a village in Ernakulam district in the Indian state of Kerala Main attractions are Onakkoor River and Onakkoor Temple.Other attractions include Edayan Lake and Onakkoor check dam (chera). Famous writer George Onakkoor is associated with this village, SH-42 High way is passing through Onakkoor. Piravom is the nearest town with markets and hospitals. The dominant religions are Hinduism and Christianity.
Onakkoor is a part of Pambakuda Grama Panchayat (പാമ്പാക്കുട ഗ്രാമ പഞ്ചായത്ത്) and is situated in Muvattupuzha Taluk .Pesse canoe
The Pesse canoe is believed to be the world's oldest known boat, and certainly the oldest known canoe. Carbon dating indicates that the boat was constructed during the early mesolithic period between 8040 BCE and 7510 BCE. It is now in the Drents Museum in Assen, Netherlands.Plano point
In archeology, Plano point is flaked stone projectile points and tools created by the various Plano cultures of the North American Great Plains between 9000 BC and 6000 BC for hunting, and possibly to kill other humans.
They are bifacially worked and have been divided into numerous sub-groups based on variations in size, shape and function including Alberta points, Cody points, Frederick points, Eden points and Scottsbluff points. Plano points do not include the hollowing or 'fluting' found in Clovis and Folsom points.Racloir
In archeology, a racloir, also known as racloirs sur talon (French for scraper on the platform), is a certain type of flint tool made by prehistoric peoples.
It is a type of side scraper distinctive of Mousterian assemblages. It is created from a flint flake and looks like a large scraper. As well as being used for scraping hides and bark, it may also have been used as a knife. Racloirs are most associated with the Neanderthal Mousterian industry. These racloirs are retouched along the ridge between the striking platform and the dorsal face. They have shaped edges and are modified by abrupt flaking from the dorsal face.Tool stone
In archaeology, a tool stone is a type of stone that is used to manufacture stone tools,
or stones used as the raw material for tools.Generally speaking, tools that require a sharp edge are made using cryptocrystalline materials that fracture in an easily controlled conchoidal manner.
Cryptocrystalline tool stones include flint and chert, which are fine-grained sedimentary materials; rhyolite and felsite, which are igneous flowstones; and obsidian, a form of natural glass created by igneous processes. These materials fracture in a predictable fashion, and are easily resharpened. For more information on this subject, see lithic reduction.
Large-grained materials, such as basalt, granite, and sandstone, may also be used as tool stones, but for a very different purpose: they are ideal for ground stone artifacts. Whereas cryptocrystalline materials are most useful for killing and processing animals, large-grained materials are usually used for processing plant matter. Their rough faces often make excellent surfaces for grinding plant seeds. With much effort, some large-grained stones may be ground down into awls, adzes, and axes.Uniface
In archeology, a uniface is a specific type of stone tool that has been flaked on one surface only. There are two general classes of uniface tools: modified flakes—and formalized tools, which display deliberate, systematic modification of the marginal edges, evidently formed for a specific purpose.Vaigai River
The Vaigai is a river in the Tamil Nadu state of southern India; it passes through the towns of Theni, Andipatti and Madurai. It originates in Varusanadu Hills, the Periyar Plateau of the Western Ghats range, and flows northeast through the Kambam Valley, which lies between the Palni Hills to the north and the Varushanad Hills to the south. The Vattaparai Falls are located on this river. As it rounds the eastern corner of the Varushanad Hills, the river turns southeast, running through the region of Pandya Nadu. Madurai, the largest city in the Pandya Nadu region and its ancient capital, lies on the Vaigai. The river empties into the Palk Strait near Uchipuli, close to Pamban bridge in Ramanathapuram District.
The Vaigai is 258 kilometres (160 mi) long, with a drainage basin 7,031 square kilometres (2,715 sq mi) large.