MEASURING THE PERCENT OF SLOPE
| Purpose: | To apply measuring and math skill in determining the steepness of a slope. |
|---|---|
| Season: | All |
| Materials: | Yard (meter) stick or measuring tape, a straight stick or board, carpenters level or flat bottle half filled with colored water |
| TEKS: | 5.1A 5.2A,B,C,D 5.4A,B 5.8B |
| Procedure: | Slope is expressed in percent, meaning the number of units the land falls (or rises) in 100 units of horizontal distance. The higher the percent, the steeper the slope. Example: a slope that drops ten vertical feet in one hundred horizontal feet is a 10% slope (vertical drop/horizontal distance times 100). |
| A transit is the most accurate instrument for measuring slope. A transit is a telescopic sighting instrument mounted on a tripod that has adjustable legs and gears for leveling the telescope. Usually a transit is not available for student use. You can measure how steep a slope is using some simple materials. | |
| Place the 50-inch stick horizontally on the ground. Put the level on the 50-inch stick, and move the lower end of the stick up until the bubble shows that the stick is level. Measure the distance from the ground to the end of the level 50-inch stick in inches. To determine percent on slope you may divide the distance from ground to end of level stick by 50 inches and multiply by one hundred or do it the simple way and multiply the distance from ground to end of level stick by two. | |
| Slope is a very important land feature. It often determines whether a piece of land should be used for grass, trees, or cultivated crops. Slope also determines the rate at which water flows downhill. Water flows slowly over a gentle slope and rapidly over a steep one. The steepness of a slope can be evaluated as follows, according to the United States Department of Agriculture's Soil Conservation Service: | |
| Nearly level (0-2%). Has no limitation on its uses. Any limitations are the result of other factors, such as drainage. | |
| Gently Sloping (3%-6%). Desirable for almost any type of development; may have erosion problems; limitations are due mostly to factors other than slope. | |
| Moderately Sloping (6%-12%). May have severe erosion problems and has a strong appeal for single-family development. | |
| Strongly Sloping (12%-18%). Has severe limitations for all types of construction. Residential development is sometimes considered because of the scenic views associated with such terrain, or when other sites are unavailable. | |
| Steep Slopes (18% and over). Undesirable for most development. May be suitable for split-level and earth-sheltered buildings, with expensive precautions. |