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5. The fifth step the technician follows is to total both Che <br />weighted values and the potential values for each item. From <br />• this, a percentage of the potential is obtained and given the <br />name of soil surface factor (SSF). This becomes the numerical <br />expression of erosion activity and is a unitless number which <br />indicates the percentage of the total potential erosion activity. <br />Vo attempt is made to differentiate between accelerated or <br />natural erosion activity. <br />The BLK has developed a classification system to separate the de- <br />gree of erosion into five erosion condition classes. Table 9 <br />shows the relation of numerical values (SSF's) to one of the <br />erosion condition classes. <br />Table 9. Erosion Condition Classes and Soil Surface Factors. <br />Class Factor Range <br />Stable 1 - 20 <br />Slight 21 - 40 <br />Moderate 41 - 60 <br />• Critical 61 - 80 <br />Severe 81 - 100 <br />These tables provide a narrative description having a similar <br />meaning throughout its area of use, in this case, throughout the <br />eleven Western States. If the procedure is used properly and an <br />individual says he has a moderate erosion condition class on the <br />Missouri River Breaks of Montana, anyone familiar with moderate <br />erosion in California will understand what he is describing. <br />Without this procedure, an individual using a term like slight or <br />critical erosion will likely be the only one who really knows <br />what he is describing. <br />6. In the sixth step, three examples, Illustrations 1 through 3, <br />have been prepared to help one understand how to determine the <br />SSF representing a given area. Each example has a rating for <br />soil movement, surface litter, pedestalling, and flow patterns. <br />In addition, for Illustration 1, the area has surface rock frag- <br />ments and potential for rills and gullies. In Illustration 2, <br />the area has gullies, but no potential for surface rock fragments <br />or rills. For Illustration 3, the area has no potential for <br />surface rock fragments, rills, or gullies. <br />L J <br />15 <br />