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J <br /> There is an upper limit to this half rule:You must also apply knowledge about maximum sustainable <br /> grades.Very steep trails will erode even if their grade meets the half rule. For example,a trail with a grade of <br /> 24 percent that traverses a steep,50-percent sideslope may be unsustainable even though it complies with the 1 <br /> I half rule. <br /> 1 <br /> 0 The Ten Percent Average Guideline <br /> Generally, an average trail grade of 10 percent or less is most sustainable.Also called overall trail grade, <br /> average trail grade is the slope of the trail from one end to the other. <br /> This does not mean that all trail grades must be kept under 10 percent. Many trails will have short <br /> sections steeper than 10 percent,and some unique situations will allow average trail grades of more than <br /> 10 percent. <br /> A trail's average grade is calculated by dividing total elevation gain by total length, multiplied by 100 to <br /> convert to percent. For example,a trail that gains 1,000 feet of elevation and is 2 miles long would have an <br /> average grade of 9.4 percent. (1,000 ft./10,560 ft.x 100 =9.4%) <br /> For trails that undulate rather than climb or descend consistently, average trail-segment grade can be <br /> calculated for certain sections. For example,a trail that is relatively flat with only one small climb may have <br /> an average trail grade of only 2 or 3 percent.In this case, it would be more helpful to evaluate the average <br /> , trail-segment grade in a critical climbing section only. <br /> Average Trail Segment Grade <br /> { <br /> r, <br /> r:�- . N, . <br /> Elev.458 feet <br /> 4% Rise=8 feet <br /> z <br /> 15% <br /> ,y�yx?. <br /> ,=A..- Run= 100 feet <br /> 8 = 100x100=8% <br /> a Average Grade=8% <br /> Elev.450 feet <br /> , <br /> t <br /> 64 <br /> Trail Solutions <br />