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Ruiliang Pu

Lab 5. Soil Loss Modeling


I. Soil Loss Modeling-- a Revised Universal Soil Loss Equation (RUSLE)

A = RKLSCP
where: A = the computed annual soil loss (T/acre/year),
R = the rainfall-runoff erosivity factor,
K = a soil erodibility factor,
LS = a topographic factor combining slope length, L, and land surface slope angle, S,
C = land cover and management,
P = erosion-countrol practice for crops.

II. Running the RUSLE Model within a GIS

1. R subfactor here is a constant = 350.

2. K subfactor is plotted in following plot. The k value varies from 0 to 1 with five classes.

3. LS subfactor is dividied into five classes shown in following plot.

4. C subfactor also is classified into five classes as in following plot.

5. P subfactor also is a constant 1 here due to no crop on the island.

III. A plot of soil loss

On this plot above, the unit in the legends is tonnes/arce/year. From the plot, the high risk areas of the basin are indicated in red color and take a certain proportion of the basin while the lowest risk areas of the basin occupy the largest proportion of the basin. In general, the size of the polygons covering the lowest risk areas seems larger than tha of other soil loss risk classes.



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