The maximum length of a base bund is recommended to be 100 meters. Permaculture building a contour bund with a plough youtube. Bund is an engineering measure of soil conservation, used for creating obstruction across the path of surface runoff to reduce the velocity of flowing water. For the love of physics walter lewin may 16, 2011 duration. Graded bund specification type of soil bottom width m top width m height m side slope. High intensity rainfall is characteristic of large areas of the sahel causing widespread rainfall runoff and erosion. A line drawn on a map or plan connecting points of equal elevation. That is what how to design various the cross section or various other parameters related to contour bunds. It retains the running off water in the watershed and thus to helps to control soil erosion. Every fifth contour line is made thicker for easy readability. When there is rainfall, contour bund acts as a barrier to the water flow and checks the velocity. Technical manual for iwmp gujarat state watershed management agency page 4 2.
The bund cross section is the same as that recommended for contour bunds on lower slopes. Manual on small earth dams a guide to siting, design and construction 64 fao manual on small earth dams a guide to siting, design and construction. Check dams a check dam is generally constructed on small streams and long gullies formed by the erosive activity of water. The base bund can be 50300 meters long, while the arms are usually 20100 meters long. In 1981, efforts were made to refine the design of the contour bunding system to increase crop yields. Bunds are not generally built to eventually extract water, but rather to add soil moisture or contribute to groundwater recharge. Contour bunding is practiced to intercept the runoff flowing down the slope by an embankment with either open or closed ends to conserve moisture as well as to reduce erosion. Nomographs to design uniform graded bund in heavy soils have been developed for various combinations of discharge, channel slope, land slope, rainfall and vegetative cover conditions. A modified contour bunding system for alfisols of the semi. In general, 400 to 500m is the maximum length of bund.
It looks a bit like a massive ditch with closed ends, trapping all of the water as opposed to having it flow anywhere. Permaculture building a contour bund with a plough. Contour bund the bunds constructed exactly on contour or with permissible deviation from the contour, are called contour bunds. Design and fabrication of bunds purging machine koruth sam k1, priyanka b2, arul. Final bunding bunding bunding it is an engineering. Bunds play a critical role in retaining moisturewater on sloped ground, providing access to fields, and delineating ownership. Ridges follow the contour at a spacing of usually 1 to 2. Narsanna demonstrates to us how a contour bund can be built with the help of a plough. Contour bunding agricultural engineering technique indiaagronet. Bunds occupy a significant portion of the arable rice production area in many parts of the world. Bunding it is an engineering soil conservation measure, used for retaining the water, creating obstruction, and thus controlling the soil erosion bunds are the embankment like structure, constructed across the land slope constructed on the contour of the area, are called contour bund when grade is provided, they are known as graded bund effective slope length of the area is reduced by dividing. One such measure, the use of stone bunds built on natural contour lines, has been promoted and supported by governments, ngos, extension agents and farmers for more. Farm bunds are constructed on agricultural land with the aim of arresting soil erosion and improving the soil moisture profile.
The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant. Bund spacing is expressed as the vertical or the horizontal distance between corresponding points on two adjacent bunds. In india, construction of bund is done by manual labour, but bullockdrawn buck. But different architects may have different approaches to this. Gatedoutlet contour bund with water stagnation gatedoutlets are shown in inset. A study was undertaken to carry out the hydrological design of contour bund cbwith surplus weir swsystem and continuous. Rainwater harvestinggroundwater rechargebunds wikiversity. Design of earthen tanks welcome to provincial irrigation. The bund retains the runoff and carries it over the distance equal to bund length in one direction. The layout of bunds on contours makes no provision for any longitudinal slope to the field. Contour bunds are preferred for construction in areas receiving annual rainfall less than 600 mm and where soil moisture is a. Design b is also a short slope catchment system, but can accommodate limited runoff from an external source. Construction of bunds is usually done by manual labour in india, but. Contour bunding agricultural engineering technique.
A contour maps consists of contour lines which are imaginary lines connecting points of equal elevation. Stone pitched contour bund this measure involves construction of horizontal lines of stone pitched contour bunds across the sloping land surface. Ideally, bunds on farms should be made on the contour line. Waste weir ww wwsurplus weirsor rubblegrass outlets are normally provided in valley points by using loose stones properly embedded in soil to avoid scouring and to drain the excess water accumulated against bund. Contour bunding helps in soil and water conservation. More of contemporary practices a look at some of the common practices adopted to harvest rain. What are the steps involved in the design of the contour. Due to their halfmoon design, semicircular bunds are well suited for planting individual trees. The diagram below shows an earth bund and a pond as if it has been cut open to show how it is designed. Contour bunding is the construction of small bund across the slope of the land on a contour so that the long slope is cut into a series of small ones and each contour bund acts as a barrier to the flow of water, thus making the water to walk. Contour bund with gatedoutlet inset system on an alfisol at icrisat center. The type of bund contour or graded bund to be constructed depends upon the rainfall and soil condition.
They are adopted to supplement the agricultural practices biological methods. Since the contour bunds are laid along the contours, they are level bunds. Plantation of live vegetation example, shrubs, trees beside the excavated bund. Bunding, also called a bund wall, is a constructed retaining wall around storage where potentially polluting substances are handled, processed or stored, for the purposes of containing any unintended escape of material from that area until such time as a remedial action can be taken.
Rice cultures are the best known example of contour bunds. So ill try to generalise it as much as possible so that it can be applicable to all scenar. In this context it is usually a waterharvesting ditch on contour, also called a contour bund. Priority has therefore been given to a range of measures for runoff and soil erosion control. Assessment of contour bunding technology for improved land and water management in mali technical document produced for the cgiar program on water, land and ecosystem wle birhanu zemadim, ramadjita tabo, bougouna sogoba, fourtet nicolas and suhas p wani science with a human face icrisat is a member of the cgiar consortium science with a human.
The bund crosssection includes base width, side slope and bund height. Contour bunds are used to prevent runoff and soil erosion and supplement. Soil erosion control mechanical measures mechanical measures play a vital role in controlling and preventing soil erosion on agricultural lands. Changing contours indicates a change of ground form. The mechanical measures include contour bund, graded bund, terraceing and contour stonewall etc. The design of crosssection of contour bund, which can store runoff excess from 24 hrs. I have worked on few heavily contoured sites myself. Overflow occurs around the tips of the bund which are set on the contour. Although the horizontal spacing is useful in determining the row arrangement. Bund design has to be adjusted according to local conditions. In addition, the lack of economic motivation has been one major constraint to increased use. Earthen bund this is the most popular soil conservation structure in the country and it is practiced at large scale all over india. A single line of stones, or a stone bund, depending upon the availability of stones, is laid along a contour. Contour bunds divide the length of the slope, reduce the volume of runoff water, and thus preventing or minimizing the soil erosion.
The following parameters should be considered for bund design. Lecture 14 will be on graded bunds, where we will be. For the sake of swale newbies, the basic concept of a swale on contour is to catch water as it drains and hold it in place until it absorbs into the ground. Height of the contour bund should be enough to store the expected peak runoff for a 10 years recurrence interval.
The design of contour bund includes determination of spacing, both horizontal and vertical and bund crosssection. Steps in design of graded bund are similar to that of contour bund. Vertical distance is commonly known as the vertical interval or v. Hydrological design of contour bund and contour trench it. Shear connection between columns and walls and between. Pdf the soil and water conservation is one of the most important components of integrated watershed program. Nala bunds are constructed across bigger streams of second order in areas having gentler slopes. In comparison to normal contour bunds, terraces even out the slope of the ground and therefore make the paddies plain. Design the dimensions of a weir used to discharge excess runoff through a contour bund for the conditions given below land slope 1 5% top width of the bund 45 cm height of the bund 60 cm height of crest above gl 30 cm 10 vi 1m length of the bund 400 m intensity of rainfall for the return period and tirne of concentration 12 cm hr. Such lines are drawn on the plan of an area after establishing reduced levels of several points in the area.
Contour lines identify all of the areas on the site that are at a certain elevation and how. Assessment of contour bunding technology for improved. Stone bunds as soil and water conservation measures in. Design a is a short slope catchment technique, and is not designed to use runoff from outside the treated area, nor to accommodate overflow. These contour lines create a water break which reduces the formation of rills and gullies during times of heavy water runoff. When water starts flowing along the fields bund becomes obstruction for it. The low soil quality combined with the limited soil moisture conditions of the harsh sahelian climate leads to a low efficiency of fertilizers. Due to the obstruction velocity reduces and water percolates behind the bunds. Design of contour bund contour bunding contour bunding is the construction of small bund across the slope of the land on a contour so that the long slope is cut into a series of small ones and each contour bund acts as a barrier to the flow of water, thus making the water to walk rather than run, at the.
Effectiveness of contour bunds and gully plugs as tools for watershed treatment introduction a watershed can be defined as an area demarcated by the ridgeline separating one drainage basin from another. The bund height should be sufficient to store the expected runoff from a rainfall of 10 years recurrence interval. Pdf nomogrpahs for graded bund design in heavy soils. The ideally a check dam is located in a narrow stream with high banks. Bunds sswm find tools for sustainable sanitation and. Graded bunds are designed to dispose excess runoff safely from agricultural field. This swale concept has also been popularized as a rainwater harvesting and soil conservation strategy by bill mollison, geoff lawton, and other advocates of permaculture. Design of the tank shape depends on the soil type, which dictates the. Contour ridges, sometimes called contour furrows or micro watersheds, are used for crop production. This course is developed to identify the fundamentals of site grading design to those. Contour bunding or contour farming or contour ploughing is the farming practice of plowing andor planting across a slope following its elevation contour lines. Contour bunds are also not successful in very shallow soils having a depth loss than 7. If the map size is large, it is written at the ends also. In other words a watershed is the drainage basin or catchment area of a particular stream or river, and the catchment area is that from which.