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Subclass T (Topography) RatingsIn Table 7, no Subclass T ratings occur because level topography is assumed . However, onsloping topography, Subclass T must be taken into account, and can be approximately determinedfrom Tables 8 and 9, which have been adapted from O.I .P . Publication No . 89-2 (16) .Soil Erosion InterpretationsSoil erosion by water can be a serious problem on many soils of the Vine-Marie map area,particularly on slopes of the varved, glacio-lacustrine silts and clays.Attempts were made to determine the erodibility (K) and potential soil erosion loss (RKLS)of soils on the Ville-Marie map sheet, using the Universal Soil Loss Equation (USLE) . Thisequation uses a widely accepted water erosion relationship, A = RKLSCP, to predict averageannual soil loss through sheet and rill erosion, where :A is the average annual soil loss ;R is the rainfall erosivity factor ;K is the soil erodibility factor ;L. is the slope length factor ;S is the slope gradient factor ;C is the crop cover factor ;P is the management practice factor ., The average annual soil loss `A' is calculated in tons/acre/year and converted totonnes/hectare/year by multiplying `A' by 2.24 . K-values were computed by the method outlinedby Wischmeier and Smith (17) . To compute these K-values, available data on surface textures andorganic matter content, was used from Table 16. Unfortunately, this data was quite limited, soderived K-values are usually only based on 1 or 2 samples . Also, there was no data for many soils,so that estimations of K had to be done by extrapolating from similar soils on the Ville-Marie sheetor elsewhere . Derived and estimated K-values are shown in Table 10 . No K-values are shown fororganic soils .In Table 10, a representative slope class has been assigned to all mineral soils, based onpublished slope information . Slope classes are described in Table 11 . Also, in Table 11, theaverage slope gradient %.nd estimated average slope lengths, have been determined for each slopeclass, and used to calculate LS-values.In Table 10, the most typical slope class was determined for each soil, and assigned theappropriate LS-value from Table 11 . Then potential soil loss (RKLS) values for bare soil, weredetermined, by multiplying R, K and LS-values together, The R (rainfall erosivity) value for theVille-Marie area was estimated to be 80 (18) .Potential soil erosion loss values for K-values and slope groups other than those shown inTable 10, can be determined from Table 12 . Potential soil erosion loss classes, descriptions andranges are shown in Table 13 . The potential soil loss class for each soil, and its typical slope class,is shown in Table 10.Table 11 shows the LS-values derived for the Ville-Marie map sheet area, and the slopegroups, mean slope gradients and mean slope lengths used in their derivation.Table 12 shows potential soil erosion .(RKLS) losses for given K-values and various slopeconditions in the Ville-Marie area .