Knowing how to dig a sloped trench in the right way can help provide extra drainage to your lawn or garden. If you have flat land and are surrounded by hills or property on higher ground, a sloped trench can get rid of excess moisture in your soil. The change in slope does not need to be very great for you have a sufficiently sloped trench.
Place stakes in the ground at either end of the area where you would like a sloped trench and stretch string between them. If you are building a long trench, you may need to add a few more stakes to keep the line straight.
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Cut the sod or the top 2 to 3 inches of soil away and fold it over next to where the trench will be. The amount cut away should be the width of your spade or the width of whatever diameter pipe you plan to install. You can replace the sod afterwords if you plan to fill in your trench.
Dig down half the length of your spade for the entire length of where you want the trench. This initial trench should be about 9 to 12 inches deep, depending on your spade.
Divide your trench into segments. Each segment should be 1/5 of the total.
Choose one end of your trench to be the high end. Starting at where you placed the first marker, 1/5 of the distance from the high end, dig down an additional 3 inches until you come to the next marker. When you come to this marker, dig an additional 3 inches for a total of 6 inches. Continue adding 3 inches of depth for each segment until you come to the end of your trench. The last section should be 1 foot deeper than the first.
Smooth out the bottom of your trench by blending the differences in depth together.