Page 72 - Nutrient Management Planning Guide

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Chapter 3.1

Figure 3.1.10 Using GPS Technology to Determine Length of Slope

Slope Length

Unlike grade, there are no regulations on slope length so there is less need for a precise measurement. There are a number of simple ways to estimate slope length including:

Estimate the length of the slope in relation to a •

known distance. Pace out short slopes. If stride-length is known and •

consistent, pacing will provide a reasonable estimate of distance covered. Keep in mind that sloping land will affect a normal stride. Use a vehicle’s odometer. This strategy should not be •

used on sites with steep slopes where there is a risk of rollover.

Slope Length in Relation to a Known Distance

A quarter section of land is approximately 800 m by 800 m (half a mile by half a mile). Based on an in-field assessment and aerial photos, a slope travels at least half the length of a quarter section. Therefore, the length on this slope would be at least 400 m.

Pacing out Slope Length

A landowner travels 10 paces up a slope at a distance of 8.8 m. It takes him 122 paces to travel the entire slope from base to crest. The estimated length of the slope is:

Slope length = average distance travelled per pace x length of slope (in paces) = 8.8 m ÷ 10 paces x 122 paces = 0.88 m per pace x 122 paces

= 107.4 m is the estimated length of this slope

Management Implications »

The grade and length of slope are natural risk factors for soil erosion due to runoff. Topography also influences the pattern of surface water flow.

In general, runoff and erosion risks increase as slope grade increases. Erosion redistributes nutrients (dissolved and sediment-bound) and organic matter within the landscape. Erosion from slopes adjacent to water bodies can increase nutrient transport to surface water. Choosing appropriate land management practices to mitigate erosion depends on whether runoff flow is concentrated or more generalized (e.g., grassed waterway versus vegetative filter strip).

more info

See template for a simple homemade clinometer (along with instructions for use) in Appendix 3.