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WAYS TO IDENTIFY THE EROSIONAL FEATURES • Highlight Seven indicators of soil movement are described and Cheir reliability for indicating soil loss (erosion) is explained. The indicators are: (1) soil movement, (2) pedestalling, (3) surface litter, (4) surface rock fragments, (5) flow patterns, (6) rills, and (7) gullies. The qualitative approximation of soil movement due to erosion has proved to be reasonably reliable. Soil Movement The real cause of soil movement on watersheds lies in soil instabil- ity. Some of the factors affecting soil instability are: (1) splash erosion, wind, velocity; (2) soil texture, structure, infiltration, and permeability; (3) slope gradient and length; and (4) cover, such as vegetation, litter, mulch, and stones. However, any disturbance of cover, such as by land use and fire, can accentuate the natural soil instability. Soil movement is most obvious during windstorms, heavy rainstorms, sudden snowmelt or when intensive land uses (livestock grazing by trampling) are occurring on loose soils. Dust clouds and muddy stream runoff as examples of obvious soil movement, but much of the soil movement occurs without such obvious signs. • A certain amount of soil movement is natural on most wildlands. Rodent and ant activity and frost heaving frequently causes soil move- ment. However, soil movement is abnormal if the soil mantle is dis- turbed to create soil losses in excess of those which occurred under natural conditions. Soil Movement Indicators A single feature of soil loss cannot be used to accurately determine the erosion condition. It must be supported by additional evidence when evaluating the erosion condition of a site writeup area or sampl- ing unit. For example, soil movement alone is a poor indicator of, ecological trend. By the time erosion is apparent, profound changes usually have taken place in cover or a drastic change in soil mantle disturbance (as shown in Fig. 6). Inadequate soil cover may be obvious as an indicator of accelerated soil movement. trhere ground cover is depleced to less than the minimum density required to protect the soil mantle, soil movement from relatively small areas may increase at an accelerated rate. A fourfold increase in soil loss as bulk density increases from 0.8 to 1.4 may occur if ground cover_S_s__ significantly decreased. ~~ -_ Other indicators of unstable soil may be Bullied drainageways with active bank cutting and sediment deposition in water bodies and at channel confluences. 27