Bunding and TerracingBooklet No. 593 Soil and Water Conservation: SWCS -11 Contents Preface I. Introduction II. Soil-Organic Matter-Moisture-Relation III. Basic Concepts in Slope Management IV. Bunds V. Terraces VI. Agro-forestry VII. Drainages VIII. Conclusion Preface In many parts of the world, farmers have been trying for many years to preserve the top soil by bunding and terracing so that they can have a continuous cultivation of the crops for their sustenance. However, many places the bunds and terraces have been made in the wrong places or wrongly made in the correct places resulting in environmental and agronomic problems. Bunding and terracing should always accompany with drainage, but it is rarely done. Slope is a major factor in determining whether bunds or terraces should be constructed for soil conservation in a given place. It is also important to systematize the theory and practice of bund and terrace making when land is managed commercially. Dr. K. T. Chandy, Agricultural Environmental Education I. Introduction Bunds and terraces are the most commonly used soil conservation measures on the cropping lands by the farmers. And yet in practice most people do not construct them properly. This booklet was necessitated by the observed inability of many trainees of soil conservation courses to conceptualize, plan and implement various types of bunds and terraces for soil conservation. This booklet is in continuation of the earlier booklets No. 47 on "Introduction to Soil Conservation". Bunds are made on cropping lands up to 6 to 8 per cent slopes and terraces are constructed on slopes ranging between 8 to 30 per cent. Bunds and terraces are the simplest of the structures and yet for the proper planning and construction, we need to know quite a bit of engineering procedures and certain theoretical calculations. These calculations are rather difficult for ordinary people to follow and yet they shall be simplified in this booklet to make them intelligible to them. Terracing should never be done on slopes greater than 30 per cent. Whereas due to the scarcity of land people are making terraces on the slopes greater than 30 percent. Before we go into the details of the planning of the construction bunds and terraces we need to see the relationship between the soil, top soil, organic matter and soil moisture. II. Soil- Organic Matter-Moisture-Relation "One foot soil decides the destiny of mankind." In this saying "one foot soil" is referred to the top soil. This saying is literally true because 80% of the food crops require only one foot soil however if there is soil we can make the upper layer of the soil into top soil in few years time by incorporating organic matter systematically. Of course we can develop top soil if there is no top soil. Soil alone consists of mineral matter from the parent rocks. but to form one inch of top soil it takes hundreds of years. In effect the soil acts like the vessel for the water. The productive part of the soil is the top soil which contains the organic matter and fertility. protein. III.to grow. Therefore preservation of top soil is the most important aspect of agricultural production activity on the land. Therefore for the conservation of water soil must be conserved first and also for the production of the crops the-top soil along with organic matter and fertility should contain enough soil moisture. without top soil very little can be produced on the land. In a human body it is the soul. soil conseveration programmes. The top soil makes the soil active and productive. The soil is like a sponge. One foot depth is referred to sufficient depth of top fertile soil required for most of the plants to grow. Fertility refers to the ability of the soil to exchange cations and anions and to supply nutrient elements to the microorganisms and plants. It makes the soil productive: "active or alive". what makes one alive and acting. Dry top soil cannot produce anything unless there is sufficient moisture. vitamins and hormones etc. Organic matter is the soul of the top soil. Now the question arises what is the relationship between the top soil and the moisture in it. The top soil is normally rich in organic matter which is the soul of the soil. command area development programmes. If soil is not there then water cannot be stored on the land. In all these inorganic and organic reactions the water does not break down but remains as an essential medium which facilitates the production process on the land. dry land agricultural programmes and the last among them is the watershed management programmes being implemented at the national and regional level. What is common between . percentage of slope and contour line. The organic matter and fertility of the soil is different from the soil as such. land development programmes. But one foot top soil can be eroded within few seconds and lost for ever from a particular locality. Everything produced by human beings on the land is grown on the top soil. it has many pores in it and the water is being held by the force of adhesion and cohesion. In our experience we find that people tend to get con. drought prone area development programmes. Soil is the vessel in which water is held. Top soil generally refers to the top one foot soil which is supposed to be suitable for cultivation of crops. It is in the presence of the soil moisture that all the organic matter and the nutrient elements are acted upon by the micro-organisms in successive stages and finally get absorbed into the crop plants along with numerous organic compounds formed during photosynthesis culminating in carbohydrate. Even if we have the best of the top soil which is rich in organic matter and all the other fertilizing elements but have no moisture then the soil will not be productive. Similarly the soul of the soil is the top soil. They are: the degree of slope. Basic Concepts of Slope Management Three basic concepts are used in describing the nature of slope which is the most important factor being considered in deciding and implementing the soil conservation measures. And all the vegetation including big trees in the world derive their nutrients except water from the top one foot soil. In other words. Organic matter refers to the decomposed substances (humus) gets mixed up with the soil. During the past several decades much importance is given to soil and water conservation in all our agricultural and animal husbandry development programmes under various names like catchment area development.fused between these two concepts. This becomes the hypotenuse of the triangle. But we may find certain parts of the rocky mountains 90 degree slope or vertical. The angle forming between the base line and the hypotenuse is the angle of slope. When we make terraces we give a slight slant to the vertical section of the terrace to maintain the angle of retention. The other two angles are the one opposite to the 90 degree angle on the base line indicating the degree of slope (hypotenuse) and the other is made by the hypotenuse and the vertical line. The cut portion of the vertical height is shown in Figure 2 in Appendix. Accordingly we can get infinite number of triangles of successive sizes. Degree of slope Degree is the unit used to measure the angle between two straight lines diverging from a common point. However it should be clearly understood when we measure the slope we can have a maximum slope of only' 90 degree. All these three . When a point (B) at any distance from another point (A) moves around to complete the full circle it has moved 360 degrees. Higher the vertical line greater will be the angle. 1. When the' slope is 90 degree it is called vertical. At 90 degree the vertical will be perpendicular to the base line. These two concepts are further explained here. But normally we don't do this. Higher the slope greater will be the degree of slope and vice versa. Complete the triangle by joining the base line and the vertical line. We can fix the length of the base as 100 units and measure the angle formed by the hypotenuse and base line either in degree or height of the vertical as percentage of the base line.these two concepts is that the slope forms the hypotenuse of an imaginary triangle which can be drawn on the down and the upper side of the hypotenuse. So slope can be measured in degree of angle or in percentage of height over base line. 2. These triangles will be identical and the corresponding angles will be same. Percentage of slope The slope of any land can also be measured with reference to an imaginary base line which we can draw at the base of the slope. Now let us consider the vertical line of triangle with reference to the base of a triangle of the same degree of angle.1 in the Appendix. We can also cut the soil vertically down to make a 90 degree slope. For the same length of the base line of a triangle the angle between hypotenuse and the base line is directly proportional to the vertical height from the end of the base line. But in all these triangles the angle made by the vertical line will be 90 degree. Greater the angle more will be the height of the vertical. The vertical line can be drawn at any point on the base line to join the hypotenuse. With reference to a point on any straight line we can make a slope or hypotenuse of a triangle at any angle except at 180 degrees angle. Any slope can be measured in the degree of angle with reference to this plain line of a leveled land. But we can use the hypotenuse of a triangle to designate the slope of a land only between 1-89 degree angle. In other words the length of the vertical line of a triangle is a measure of the angle. Both triangles together make a rectangle as given in Fig. A well leveled land can be represented by a straight line for which the angle of slope will be 0 degree. On this imaginary plain line at any point we can draw a vertical line of a certain height at 90 degree angle. Depending on the degree of angle the height of the vertical line varies: lesser the angle shorter will be the vertical height and vice verse. Normally no natural land of soil will be 90 degree slope. Beyond 90 degree we can not have a slope. Angle of the slope means the angle between the slope line and the base line. In other words normally the slope of the land is measured only between 0 to 90 degree. But for ordinary people such instruments may not be available. The materials needed for measuring the slope are: (1) two sticks of five to ten feet length and graded in inch or centimeters. Therefore the percentage of the slope is calculated using the formula h/b x 100.00 Height (ft) 0. Measure the height on the vertical stick from the ground to the point where the horizontal stick is touching the vertical one. percentage.5 18. Correlation between degree and-percentage of slope There is correlation between the degree of slope and percentage of slope as shown in the ready reckoner table 1 given here.angles in all the triangles will be same however big or small they may be.No. The following method may be used effectively in the field conditions. i. The angle between the base line and hypotenuse is the degree of the slope and is measured using the protractor. But for each length of base line there will be a corresponding vertical line. Measurement of degree & percentage of slope Measurement of the slope can be done using several types of instruments. slope I % = h/bx100 where h = height of the vertical line and b = I length of the base line. Higher the vertical line greater will be the slope of the land. (4) paper. To measure any slope first of all plant vertically one of the sticks at any point on the slope. The angle is 90 degree. the vertical will be the same for any number of triangles. Now in the case of measuring slope in terms of percentage we fix the base line to 100 units of measurements and then we measure the vertical height for the same angle of slope. Plot a triangle on the paper in appropriate scale.80 . Therefore percentage of the height of the vertical line is the expression of the percentage of the slope while the base line is fixed at 100 unit length. Similarly measure the length of the horizontal stick from the slope to the vertical stick. Degree.00 10.5 Base length (ft) 10. Let us assume that the base is 5 ft and the height 2 ft. (3) students geometry instrument box with all the instruments. pencil and eraser. base and height relations of a slope Sl. for every 100 unit length variation in vertical length indicates variation in the degree of slope. Use the spirit leveler to check the horizontality of the second stick. 1 2 Degree of slope 5 10 Percentage slope 8. The length of the horizontal stick will be the base of the triangle and the height will the vertical line of the triangle. The formula for calculating the percentage of slope is h/b x 100. 3 of Appendix. 3. Estimation of the percentage of slope is depicted in Fig. In other words. Place the other stick horizontally in such a way that one end of this stick touches the slope and other end touching the vertically planted stick. The percentage of the slope is calculated from the same measurements of the base (b) and height (h). This means for the same angle we can have any length of the base line. So the degree is measured from the plotted triangle. Table 1. Then the percentage of slope is calculated by applying the same formula and we arrive at 2/5 x 100 = 40% slope. 4.e.85 1. For a particular angle of slope and 100 units of length of the base line. Draw the hypotenuse and complete the triangle. In all the cases the angle of slope remains the same. (2) a spirit leveler. 0 100 10. The total length of the slope is determined as a requirement for estimating the number of bunds or terraces to be made across the slope.0 10. Contour line is an imaginary line joining all the points at the same height from a common base line.40 10.00 It should be noted from the table. The contour line across any sloping land can be traced by using the "A" frame. 5.0 84. 6. If the slope is uniform the plots between bunds . The land sloping between 30-100 per cent or 17-45 degree and is planted under forestry. Under no circumstance the soil of this land should be stirred up. at 45 degree angle the percentage of slope is hundred. In other words any slope which have a vertical height of 5.8 36. We should leave it for natural forest.75 ft or more for every horizontal distance of 5. is tied at the top joint of the "A" frame and is allowed to hang down. If it is placed on a sloping land then the string will show the deflection to the slope side. Thus we can take a number of points across the slope by moving and adjusting the "A" frame across the slope.66 5. The "A" frame consists of a wooden frame exactly like the capital letter "A" in the English language.3 4 5 6 7 8 9 15 20 25 30 35 40 45 26. Slope length also can be measured between two points on a slope. with a small stone or any other weight. Contour line Contour line is the third important concept often used in the slope management. Mark the point of the second leg as the second point.00 10.4 46. A string. Mark the third point. When the "A" frame is kept on a well leveled ground the string with the weight will remain exactly at the middle of the cross beam of the "A" frame. But the field level the " A" frame is used.00 8. Next place the first leg on the mark of the second point and adjust the second leg in such a way that the string will remain in the middle of the cross beam.64 4. It is called contour line because all the points in that line will be at the same height from the sea level or a common base line.6 57. Even without any reference to the sea level height any one can draw a contour line with the help of land survey instruments like dumpy level etc.00 2.7 70.00 10. Slope length The length of the slope is the total length of a sloping land measured along the slope. The ultimate base line usually considered is the average sea level.00 ft should not be cultivated even for perennial crops. Beyond 45 degree angle we need not consider any land use pattern. It should be kept in mind while implementing soil conservation measures that beyond 30 % slope no agricultural operations should be done on the land.77 7.68 3.00 10. When we join these points we get the contour line. Place one leg of the "A" frame at any point on the slope and adjust the other leg in such a way that the string remains in 'the center of the cross beam. 3a and 3b in the Appendix dices the "A" frame at different levels.00 10.00 10. A base line can be fixed at the any point at base of the slope and all the contour lines can be drawn with reference to this base line. Fig. The land above 100 per cent or above 45 degree should be placed under permanent forests. Bunds are ridges or embankments or long and narrow projections constricted on the surface on the land at selected places and in selected directions. 1. lateral bunds. side bunds. The top width will always be less or at the most equal to one-third width of the bottom width. Graded bunds When the contour bunds are made with slight deviation from the contour line towards one direction to drain out the surplus water that may occur during the rain. Contour bonds When bunds are constructed across the slope in a contour line they are called contour bunds. The length of the slope is also a factor to decide the number of bunds and terraces to be made. The earthen dam is also a bund. But in the case of graded bunds the side bund is constructed as part of the drainage channel on the side towards which the water is drained. Side bonds Side bunds are the bunds that are constructed at the extreme ends of the contour bunds along the line of slope. For a casual observer the graded bunds look like contour bunds. 3. They are constructed to reduce the length of the slope by dividing slope into different sections and to impound the running water at different sections to increase percolation. The length of the slope is a parameter that is considered for the management for soil conservation. For the same height and width (top and bottom) the bund can be of any length in any direction. The bunds may be of different sizes and heights and constructed for various purposes. 2. Greater the length more will be the soil erosion. but is constructed to stop and store large amount of water coming down through a river: for example Hirakud darn. Bunds have a top width and a bottom width. But if the slope of the slope-length is not uniform then the size of the plots between bunds and the terraces will not be uniform. Bonds Bunds are the most common soil conservation measures adopted by people in most of the cultivated lands. Sometimes the top may be made round instead of flat. They are normally constructed on lands with 1-6 per cent slope. If the slope of the slope-length is not uniform and the slope length is in contour lines.and the terraces will be of uniform size. But side bunds are constructed on both sides of the contour and graded bunds. Bunds are usually made on lands less than 8 % slope. Graded bunds are made on land with slope between 2-8 per cent. A. Lateral bonds Bunds constructed along the slope between two side bunds in order to prevent concentration of water along one side and to break the length of the contour bund into . graded bunds. marginal bunds and shoulder bunds. the plots and the terraces will be irregular. IV. But bunds may be constructed up to eight per cent slope. Types of bonds Depending on the purpose the bunds are classified as contour bunds. Between two bunds is the space of land either terraced or left unterraced and used for cultivation. they are called graded bunds. 4. 10.convenient bits are called lateral bunds. However all these rules and calculations can be reduced to some simple guidelines as following. Shoulder bonds Shoulder bunds are those constructed at the outer edge of a terraced plot. bottom width and the slope of the sides of the bunds. These calculations are difficult for ordinary peopIe. river or stream margins. Besides there are a number of calculations to decide the height. These depends on the slope of the land. 4. One should be able to walk over the bunds as a path without their getting destroyed or sunkened. 5 in Appendix. never from the upper side. are made in contour lines. Like the side bunds the lateral bunds also should be accompanied by drainage channel to drain out the excess of rain water. It has a wider bottom.the bund is constructed on a plain ground. The slope of the side of the bunds is around 1:2 to 1:2. When contour bunds are made on the slopes the length of the lower side slope of the bund will be longer than the length of the upper side slope. boundaries. 1. The normal structure of a bund on the plain land and on slopes are depicted in Fig. 3. gully margins and the like are called marginal bunds. To the ordinary man they all may be confusing. Regarding planning of field bunds the readers will come across literatures and engineers with different theories and practices. The distance between two bunds of the same height are kept in such a way that lower bund should be 30 cm higher than the bottom line of the upper bund. Structure of a bond The basic structure of the bund is trapezoidal. When a terraced plot is used for wet paddy cultivation it is bunded on the outer side in order to retain the water. 6. two sloping sides and a height. In other words the slope of the upper side of the bund will be steeper than the slope of the lower side even in the clay soil. The minimum slope of the sides of the bunds would be 1:! for clay soils. Marginal bunds Bunds constructed along margins of the watershed. 7. the top width. 5. Usually the lateral bunds are constructed when the contour or graded bunds are more than 300 metres long. 9. B. 6. 2. Some times shoulder bunds are constructed in order to prevent the rain water flow out of the terraced plot and thereby allow more percolation into the plot. narrow top width. Normally the top width of the bund is made equal to the height of the bund 5. the amount of rain fall of the place. 12. They serve as boundary bunds. 8. Take the bottom soil for bund making and save the top soil. Take the soil for bund making from lower side of the bunds. The area of cross section of the bund is maintained around one square metre for field bunds. The sides are equal when . . The bunds on a gently sloping land for soil conservation. 11.5 for loamy soil. The slope of the side of the bunds is around 1:3 to 1:5 for sandy soil. The maximum height of the field bunds is not kept more than 80 cm. the vertical interval of bunds and the type of soil. But when they are constructed on a slope the bottom of the bund will be the same as the slope of the land and the side of the bund on the slope side will be more than that of the side on the bund on the upper side of the slope and as a result the basic trapezoidal structure is changed. road margins. Check periodically the alignment of the contour line and the dimensions of the bund being made. There are a number of theoretical and practical aspects for the construction of the bunds according to various literatures and engineers. This strip of land between the bund and the area from where the bund-making soil is taken is called berm.The shape and structure of the bunds are adjusted according to these twelve guidelines. 12. The dug up soil is placed on the stirred up area and gradually make the bund as per dimension of the bottom width. The stone gathered while digging the bottom soil may be placed on the berm as a basal support to the bund being made. Compact very well every basket of soil placed for the bund making. Demarcate the area on the slope occupied by the bottom of the bunds. 16. Demarcate the area for taking the bund-making soil leaving about 30 -45 cm away from the lower edge of the bottom side of the bund. the berm and the area from which the bund making soil is taken and the channel between berm and the plot (See Fig. 3. These procedures are more suitable for the construction of contour bunds and graded punds. Note the area from which the bottom soil is to be taken to make the bund. C. However some simple guidelines may be given as follows. 4. the height and the slope of the sides of the bund. Estimate the bottom width. Employ enough people specially for compacting. 7. Slightly stir the soil of the area where the bottom of the bund will be resting so that the newly placed soil may be well jointed with the bottom soil already there. Construction of bund While constructing the bunds care should be taken that the top soil is not used for the bund making. However placing too many stones may not be advisable. Still excess drainage water is there make a common drainage from the all the trenches of all the plots. Demarcate the contour lines of the bunds at distances . 5. For this the top soil from the area which will be occupied by the bund and the area from where the soil is taken for the construction of bund should be scraped off and be kept aside and later it is spread on the place from where the bottom soil was taken for the construction of the bund. Suitable adjustments and modifications are done for the construction of other types of bunds. They can be better burried in the bund itself. Scrape the top soil from these areas except berm and keep it at the lower side. If one wants to level gradually the land between two bunds take bund making soil only from the lower side of the slope in relation to the bund. 8. following the first guide line given regarding the structure of the bund. The bottom soil is dug up in uniform depth from the area from which the soil is to be taken for the bund making. 5 in Appendix). height and the slopes of both sides of the bunds. . 10. Plant suitable trees on the bunds which will be allowed to grow straight up by pruning the branches periodically. The procedure is as follows. 9. 13. 14. After the construction of the bund is over the top soil is pushed into the area from where the bund-making soil was taken. 15. 6. If graded blinds are made leave a trench of suitable width and depth just next to the berm on the lower side while filling the excavated area with the top soil and make a proper outlet for the excess water at the end on the graded bunds to drain out into the trench from the upper side. 1. 2. These may be unintelligible to most of the people who want to construct the bunds in their field. top width. 11. top width. 17. broad bench terraces. One has to make his own decision on the width of these four types of terraces. 6. stones and any type of vegetation etc. Bunds made of cement and stones. At times one may come across different types of classification of terraces based on the width and percentage of slope. The choice of the material depends on their availability. S is percentage of the slope. Bunds made of mud or soil. broad bench terraces made on slope between 12 to 20 per cent. Greater the slope lesser will be the width of the terrace for the same height of the cut portion to make the terrace. 12. Bunds made of stone or bricks on one side and other side soil. Bnds made of stones alone by arranging them heaped in a line. Terrace is cut and leveled portion of land on a slope. From the names anyone can understand the constructional materials needed the shape it assumes while constructing and the constructional details. Terracing Terracing is perhaps the second most commonly used method for soil conservation cropping land. bench terraces made on slopes between 20 to 25 per cent and narrow bench terraces made on slopes between 25 to 30 per cent. A. Bunds made of soil and grasses or bushes and trees. 4. 10. Bunds made of stones and soil together. Width wise though tour types of terraces are named. Make sure that the plants grow well and straight up. 11. purpose. 9. bench terraces and narrow bench terraces. finance. Bunds made of cement and bricks. 9. Three dimensions are taken into consideration while planning to construct terraces: (1) width of terrace. 5. These three are related to each other as shown in the formula VI = W x S/100 where VI is vertical interval. (2) vertical interval of terraces and (3) percentage or degree of slope of the land to be terraced. 2. strength and . 7. Bunds with double walls on both sides made of stones or bricks with cement or clay with lime. V. durability required. Width Depending on the width the terraces are divided into broad bed terraces or broad base terraces. D. Bunds made of a combination of soil. Construction material Bunds are mostly made of soil though they can be made of any material. W is width of the terrace. 8. Repair bund in case any damage occurs during the construction period. slope and the material used for the construction of the terrace wall. Bunds made of wood and soil together. Broadly we can say that broad base terraces are made on slope between 6 to 12 per cent.18. No clear cut divisions are there between these tour types. The width of the terrace depends on the degree or the percentage of slope. 3. Terraces are classified on the basis of width. Bunds made of clay and bricks. 14. 19. Bunds made of clay and stones. Depending on the material the bunds may be classified in to the following. Bunds made of wire mesh and stone like gibbons. Bunds made of wood or wooden pieces. . 1. 13. 10.50 0. vertical interval. 5.00 1.00 Width of the terraces (metres) 20 10 5 0.00 2.60 Using the formula VI = W x S/100 one can estimate VI or W or S for any two of them are known and thus the table 2 can be expanded for any percentage of slope or for any vertical interval or for any width of the terrace.04 0.75 4.25 2. the width of the terrace (W) to be cut is 5 metres. a) Keep the maximum width of the terraces up to 50 metres when the slope of the land is 2 per cent.0 12.50 9. 15. Though theoretically speaking we can make terraces on slopes up to 100% or 45 degree angle it is strongly discouraged not to make them on slopes beyond 30% or 17 degree.10 0.00 1.50 0. Find out the vertical interval (VI). The vertical interval in this case will be one metre.00 4.50 6.00 1.50 0.00 0.40 0. While making the terraces the cut portion of $e land will not be exactly vertical but .5 metres Similarly we can find W or S if we know the rest of the parametres.60 1.50 5. The slope of the land normally to be terraced vary from 2 to 30 per cent and hence the width and the vertical interval too will be varying.25 6. But all these may be simplified as follows. 25 and 30 per cent slope. For example let the percentage of slope (S) be 10.30 0.00 2. Vertical interval in Metres of bench terraces on various slope with various widths Slope % 2 5 10 15 20 25 30 50 1.00 7.00 0. Table 2.6 metre. Construction There are a number of calculations recommended to be done while planning for construction of terraces. Applying the formula VI = W x S/100 VI = 5 x 10/100 = 0. The width of the terraces is also known as horizontal interval. 20. 1. The VI and W for other slope-percentages can be calculated using the formula VI = W x 5/100 as already given earlier. In general it can be said that lesser the slope greater will be the width and lesser will be the vertical interval and vice versa.50 1. The vertical interval in this case will be 0.40 0.00 2.50 3. (2) terraces of same width and varying vertical interval and (3) terraces of varying vertical interval and varying widths.00 3. The percentage of slope is already explained.50 10.10 1. When the slope is more than 100% or 45 degree angle the width of the terraces will be less than the.00 7.20 0. Once we have estimated the slope of the land to be terraced we can construct the terraces in three ways: (1) terraces of same vertical interval with varying widths.50 3.00 1.20 0.50 15 30 0. Table 2 is a ready reckoner for anyone who would like to plan for terracing of land with 2.50 2 0.00 5.The vertical interval means the vertical distance between two terraced. b) keep the minimum width of the terraces up to two metres when the slope of the land is 30 per cent. e. Secondly we retain the top soil and use it while the plot is being leveled gradually. Kinds of terraces Depending on the direction of slope terraces are classified as level bench terraces. outwardly sloping terraces and puerto type of terraces. Outwardly sloping When the terraces are sloping outwards they are called outwardly sloping 1erraces. potato. Inwardly slopping When the terraces are sloping towards the hill it is called inwardly sloping terraces. d. Hence the actual width of the terraces will be a little less than the calculated width. As a result the cultivation of . Level bench terrace When the terrace is well leveled it is called level bench terrace. But in this case 'no filling is done soon after the bund making as in the case of other types of terrace making. Stone walled terraces Terracing the sloping land is an ancient way of land development for agriculture. But always take soil from the bottom side of the bund for the bund making.eled automatically. In this method we can save the labour and the expenditure on the cutting and transferring of soil from the upper side of the plot to the lower side of the plot. On this slopes one can plant fodder grasses like napier grass or any other type of perennial grass which will retain the slope as well as give some yield of fodder. Most of the terraces are built with mud walls which collapse very frequently. This method of terracing is possible only on slopes less than 5 to 6 per cent. vegetable are grown they need drained soil The slope is given to the terraces in order to drain out the excess of rain water. harrowed and cultivated from the lower side of each plot turning the sliced soil each plough line towards the lower side. Sometimes we may have to raise the bund further as the plot gets leveled. Such terraces are built in dry land areas so that whatever rain comes maximum run off water is collected and sunk into the land. Puerto type terrace In Puerto type of terracing leveling is done gradually by cultivation. This types terraces are more suitable for the medium rainfall areas. Bunds are constructed on the place where the terrace wall would have been positioned. Fig 6 in the Appendix -.. The vertical interval between the terraces are made very slanting and occupies some space. c. When crops like maize. Instead the land is ploughed. When crops like paddy and sugar cane are planted water should be impounded.slanting sufficiently to maintain the angle of retention. They are briefly explained here. This method also may not be suitable for areas with high rainfall which erodes the top soil in most of the cases. Each terrace in this case will slope towards the hill ending in a ditch or drain which will collect and sink the water into the soil. b. Gradually the plot becomes lev. Between two bunds we get a sloping plot which is usually leveled while making the terraces. When wet paddy is cultivated in terraced lands each terrace will be bounded by a bund to impound the rain or irrigation water.' depicts the different types of terraces. Slopes greater than this will not be able to retain the soil from the influence of erosion forces when it is being cultivated and cropped. 2. a. inwardly sloping terraces. is very good for fodder and green manure purposes. In the short run they can get fodder. green manure and some fruits and in the long run they get substantial amount of money by selling the timber. Similarly the terrace walls can be made of bricks. Shisham and jackfruit trees are very suitable for growing on the bunds and edges of the terraces. Where stone are not available burned bricks or cement hollow blocks can be used. The method is briefly explained as follows. Besides quite a lot of top soil is lost tor ever. The stones are arranged in such a way that on one side they are in the same plane as we see in any wall. They are multipurpose trees excellent as timber trees. All the fruit trees that need pruning or can withstand pruning like jackfruit trees and drumstick trees also can be planted as agro-forestry on the bunds and the edges of the terraces. VIII. They are planted better in the east-west direction. Other trees suitable for agroforestry are subabul and mulberry. Whereas the inner side the stones are positioned in irregular manner and the gap between the mud wall and the arranged stones is packed with soil so that the soil becomes a binding force between the stones. Shisham being a legume. Demarcate the line of terrace wall. But they can be planted in any direction provided they are kept pruned of their branches and made to grow straight upwards. Terraces are permanent assets which will give regular income if they are cultivated properly. They should be permanently made/with non collapsible walls.the collapsed area is disrupted and the possible income is lost for few years. Planting trees on the edges of the stone walled terraces is not advisable as they may break the stone walls. 4. It can be straight line or contour line. 3. VII. 1. The terrace wall takes about one year to establish itself and well established stone wall will last many years and the terraces can be used for any type of cultivation. Establishing agroforestry on the bunds and edges of the terraces is very profitable in the long and short run especially for the small and marginal farmers. . Drainage. In other words the angle of retention is maintained while arranging the stones. The stones are arranged one above the other in such a way that they are able to withstand the force of gravity and maintain the angle of retention. Collect enough stones from the surrounding areas or bring enough bricks. Dig up trench of about one to one and half feet as a foundation for the stone wall. The full length of the wall is completed to a height sufficient enough to have its height a little higher than the bottom of the upper terrace wall. firewood. This is possible wherever stones are available abundantly. for fire wood. 2. One can always find a few suitable species of multipurpose trees every place in India. cement blocks etc. One sided wall is built. Agro-forestry On the field bunds and the edges of the mud walled terraces suitable timber or fire wood trees can be planted. In this matter we can learn from the experience of people in some parts of the world where they make terraces with walls built of stones packed with soil. By ramming the soil and cementing the botrom and the side of the pond we can make the ponds impermeable to water. In the case of terraced land depending on the amount of the excess water one or more terraces may be made into ponds into which the excess water is stored and at the time of scarcity the same water is used for irrigation purposes. fodder crops etc. growing fruit trees. Depending on i the area the water can be used for all types of agricultural I purposes like vegetable growing. Several side drains can be joined together to form a common drain. Besides repairing of the bunds and terraces is an unproductive work and expenditure. Farming is no more a traditional occupation. broad base terraces are made on slopes between 6 to 12% slope. The drainages are better established at the inner side of the terraced plot. it has become a business in which science and technology are applied just like in any other field of human involvement. Conclusion Bunding and terracing are the most common soil conservation methods employed by farmers from the ancient times onwards. People followed these methods traditionally to develop their sloping lands to conserve the soil for cultivation. Several side channels may be joined together to form a common channel to drain out all the excess water from an area bunded for agricultural purposes. The stored water in any trench can be utilized by simple siphoning out whenever needed. Drainages from several terraced plots can be drained into a side drain. If we are able to store water more than six months in these ponds we can go for fish rearing as an additional income. Similarly drainages should be established in each terraced plot. At times the extent and depth of erosion is such that it cannot be recovered at all. We need to have proper and scientific understanding of the theoretical and practical aspects of the bund and terrace making so that even people who are not traditionally the farmers can make them and develop a sloping land. Slope is the major factor that decides whether one should go for bunds or terraces over a given place. . Due to lack of proper drainage facilities in most places the bunds and the terraces are broken almost every year causing loss of top soil and crops. VIII. The excess water can also be stored in deep and wide contour trenches constructed at suitable places in the land.In high rainfall areas or in areas where there is overflow of rain water from the bunded and terraced areas providing effective drainage system is an important factor for the stability of the bunds and terraces. social and agro forestry. These trenches can be made impermeable to water by cementing the bottom and the sides. The best way to use the excess rain run off water is to collect them into ponds or into earthen tanks. broad bench terrace on slopes between 12 to 20 % slope and bench terraces on slopes between 20 to 25 per cent and narrow bench terraces on slope between 25 to 30 per cent. Bunds are recommended on slopes up to 6%. In high rainfall areas graded bunds are made instead of exactly the contour bunds and excess rain water is drained out from all the contour bunds or some of the contour bunds through a side channel. Depending on the amount of water several ponds can be constructed to collect the water from few side channels or from the common channels. Excess drainage water should be collected in well constructed trenches and ponds located at strategic positions in the land. It is foolishness to make bunds and terraces on the agricultural land without the drainages. .Well laid out drainage structures should be part of the bunded and terraced land. . %%%%%%%%%%%% .