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Accelerated erosion can occur from surface erosion processes due to exposed bare soil, compaction, and poor conservation practices (e.g., by agriculture, surface mining, land clearing, and silviculture). Surface erosion occurring on steep, highly dissected slopes has a higher potential of conversion to stream-transported sediment due to rill and gully erosion. This risk needs to be considered for various surface disturbance activities that potentially affect such processes. A flow chart depicting the assessment methodology at this level is shown in Flowchart 9. The information needed to make this risk assessment is
| a) | Total acres being evaluated for a sub-drainage and soil type erodibility potential |
| b) | Acres impacted |
| c) | Per cent bare ground of impacted acres |
| d) | Drainage density of impacted slope or width of interfluve spacing |
| e) | Slope position and gradient (identify if highly dissected slope) |
| f) | Distance of disturbance to nearest stream |
| g) | Buffer width of riparian corridor |
The data entry, calculations and summaries are recorded on the surface erosion/sediment delivery risk rating worksheet (Worksheet 8, PDF, 72 kb, 1 p). The basic relation used to obtain risk ratings are located in Figure 76.
Sediment delivery potential ratings are obtained through the relations in Figures 86, 89, 90, 91 and 98 (see below). Summaries for the risk ratings are shown in Figure 75. Potential risk for surface erosion can be lowered for specific land uses with site-specific mitigation. If risk ratings are high to very high, then advancing just those identified acres and locations to the PLA is recommended.
The results are again summarized individually by sub-watershed in Worksheets 5a & 5b and for multiple sites/sub-drainages in Worksheet 6.
Worksheet 5a: Printable PDF (10 kb, 1 p.) | Excel Spreadsheet (27 kb)
Worksheet 5b: Printable PDF (9 kb, 1 p.) | Excel Spreadsheet (35 kb)
Worksheet 6: Printable PDF (8 kb, 1 p.) | Excel Spreadsheet (21 kb)
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