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CONTOURS & WATER IN THE LANDSCAPE

CONTOURS & WATER IN THE LANDSCAPE. CONTENTS: What is contour, and why is it important? How can I use it to help my farm designs? What tools can I use to find it? Contours and maps. How do people use contour on the farm?. What is contour? Why is it important?.

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CONTOURS & WATER IN THE LANDSCAPE

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  1. CONTOURS & WATERIN THE LANDSCAPE CONTENTS: • What is contour, and why is it important? • How can I use it to help my farm designs? • What tools can I use to find it? • Contours and maps

  2. How do people use contour on the farm? What is contour?Why is it important? • A contour is a flat line across a slope at the same level. • Water runs down a slope crossing contour. • Farmers can use contour to design systems that… • Slow water and protect against erosion in the wet season • Harvest nutrients and soil that has eroded from higher slopes • Keep more water in the soil for plants in the dry season. • Hold water for plants or animals that love water (e.g. rice, taro, fish, eels, ducks, etc).

  3. Swales (1/2) How can a swale be used to catch water, nutrients and eroded soil before it leaves your farm? What is a swale? • A swale is a ditch on contour across a slope, with the soil put in a mound on the downhill side of the ditch. • It slows the water, protects against erosion, and allows water to absorb into the land. • Swales can also be connected to ponds or dams to increase their water catchment area.

  4. Swales (2/2) If there are very big rains in the wet season at your farm, how should you design a spillway on the swale? e.g. low/high? wide/narrow? When it gets FULL… • The designer can choose where water will overflow from the swale using a spillway. • Spillways should be wide and flat to avoid erosion. • The height of the spillway should be no more than half the height of the swale mound. Where is a good place to make the spillway?

  5. Ponds and Dams What are ponds and dams? • Ponds and dams are designed to hold water and can be used for many purposes • irrigation and washing • aquaculture (fish, shrimp, water plants) • wet terraces (rice, etc) & chinampas • Ponds and dams on a slope can connect with water systems for plants, animals & houses below (downhill). • The higher the pond or dam is above the outlet, then the more pressure is in the water pipe. • Ponds or dams connected to swales have much larger catchment areas & more volume. What is the difference between a pond and a dam?

  6. Terrace Fields & Contoured garden beds Terrace fields are similar to swales, with 2 differences: • the ditch is wide and shallow • usually level • often filled with water or mud e.g. growing wet rice • the mound is very small and is often made of soil that holds the water • Garden beds that are designed on contour work like swales too • They trap nutrients and hold water • Footpaths around the garden beds to irrigate more efficiently than using a hose or water-can.

  7. Alley Crops What are alley crops? • Alley crops are long thin crop areas (alleys) on contour. • Often they use functional plants such as legume trees in between the alleys to protect and help the crops to grow. • Alley crops help to slow water and improve production. • They can be used for: • Trees for timber, firewood and mulch • Animal food • Legumes to feed the soil • Protection for crops (erosion, wind, sun) • Feeding areas for animals e.g. chicken tractors and ducks What could you use alley crops for on your farm?

  8. Other Uses of Contour Can you think of any other uses of contour?

  9. Tools to find contour- A-frame Materials • 2 x 2m sticks • 1 x 1m stick (this stick must be straight) • String, nails or vine to join the ‘A’ frame legs together • 1.5m string • 1 x weight, e.g. a rock Steps • Connect the two long sticks together at the top and then connect the short stick across them so that you have made a shape like the letter ‘A’. • Tie the string to the weight (e.g. rock) so it hangs just below the short stick. • Mark where the 2 ‘feet’ of the A-frame touch the ground. • Let the weight stop moving and mark where the string crosses the short stick. Turn the A-frame around (swap the feet) and mark it again. • Measure with a ruler, and draw a clear line halfway between the marks. This is the centre line. • Now wherever you move, if the string is on this line then the A-frame is on contour.

  10. Using the ‘A’ Frame • Use a bamboo or wood stake to mark the start point on a slope. Put one foot of the A-frame at the stake. • Move the other foot of the A-frame until the string is on the centre line. Mark this foot with a second stake. • Keep repeating and soon you will have marked a contour on the slope!

  11. Tools to Find Contour- Water Level Materials • 2 x 2m sticks (straight) • 10m thin clear plastic tube • Wire or string • Measuring tape or ruler • Pen • Water Steps • Using the measuring tape or rule mark cm’s on one of the sticks starting with 0cm at the bottom. Then take the other stick, stand it next to the first stick and copy the marks. • Attach the ends of the clear plastic tube to the sticks using wire or string. • Fill the tube with water until the it is half way up the sticks. Remove all the big air bubbles. It will not work with air bubbles in the tube.

  12. Using the Water Level You will need two or more people. • Put a marker at the start-point on a slope. Person1 stand with one end of the Water Level (vertical) at this marker. • Person2 take the other end of the Water Level and move a few metres away. Move a little bit up and down the slope until the water is at the same level on each end of the Water Level. Put another marker here. • Repeat to find the contour. Tips • The person with the smaller number on their stick, is on higher ground. • When moving, put your finger over the end of the tube. • The difference in the measurements is the height difference between the sticks.

  13. Contours on a Map • Some maps have contours drawn as lines to show the shape of the land. • sometimes the lines will have a number on them, to show how high the contour is above sea-level. • The level of each contour line is X metres above or below the contour lines next to it. • X is called the contour interval. It will be written somewhere on the map, maybe near the key or legend. • The closer the contour lines are together, the steeped is the slope. • Water moves down a slope and across the contour lines. • After some practice, you can understand the shape of the land by looking at the contour lines. • mountains, valleys, ridges… • You can see where would be a good place for a swale, a dam, or a spillway.

  14. Protecting the soil with Contour • Soil is the basis of all ecosystems • Soil the most important resource for farming and we must take care of it… • especially where it’s already not ideal (HEPA). • It can take thousands of years for a few centimetres of good soil to develop… but only a few hours to lose it by erosion when it rains. • Using contour in these ways can help to: • stop erosion and catch organic matter, • maximise water in the landscape, • save energy, and • encourage diversity and life on your farm!

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