PART F - HOW TO MEASURE SLOPES
Slope is a comparison of the amount of rise or fall of the ground as compared to a
known distance on the ground. In order to determine the percent of slope of a
given area, you must know how much horizontal distance on the ground there is
between contours, and how much ground distance lies between two index contours.
The horizontal distance (distance on the ground measured on a plane) is obtained by
making a measurement on the map in the following manner:
* Locate the high and low points on the map.
* Place the edge of a piece of paper on the map so the edge touches the two
* Make tick marks on the paper where it touches the two points on the map.
* Move the paper to the bar scales in the marginal data of the map and measure
the distance between the tick marks.
* Record the distance obtained from the measurement.
The vertical distance (rise or fall of the ground) is obtained by:
* Finding the elevation of the high and low points.
* Subtracting the elevation of the low point from the elevation of the high
Now the vertical distance (VD) and the horizontal distance (HD) are known the
percent of slope can be determined by using the following formula:
VD X 100 = Percent of slope