LIFE+ Programme (European Commission)
LIFE08ENV/IT/000428
EXPLAINATION OF THE DATA AND MODEL OF SOIL EROSION
UPLOADED IN THE SICILIAN FRAMEWORK OF THE SMS (27/04/2011)
1 SOIL EROSION RISK USLE MODEL .............................................................................................. 2
1.1
CALCULATION OF R FACTOR .......................................................................................... 2
1.2
CALCULATION OF K FACTOR ......................................................................................... 2
1.3 CALCULATION OF C FACTOR ................................................................................................ 3
1.4 CALCULATION OF L FACTOR ................................................................................................ 3
1.5 CALCULATION OF S FACTOR ................................................................................................ 3
1.6 MODELS FOR SOIL VULNERABILITY AND SENSIBILITY TO WATER EROSION........ 3
1.7 MODEL FOR EROSION RISK ................................................................................................... 4
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1 SOIL EROSION RISK USLE MODEL
1.1 CALCULATION OF R FACTOR (file name: r)
The calculations are based on climatic data of UCEA.
We calculated for every station the R factor with the next formula:
R factor = Σ (MMPi2 / MAP)
Where MMPi are the mean monthly precipitation of the ith month (January, February…)
MAP is the mean annual precipitation
This calculation has been done for every meteorological station and than the R factors has been
interpolated by regression kriging to obtain the R factor grid of Sicily.
1.2 CALCULATION OF K FACTOR (file name: k)
For the calculation of the K factor, data on soils texture and soil organic carbon content have been
obtained from the Pedological Map of Sicily (1:250.000).
The K factor has been calculated on the base of the next table:
Organic matter content
FIND K VALUE ACCORDING TO
TEXTURE SYMBOL AND
ORGANIC MATTER %
Sand
Loamy sand
Sandy loam
Loam
Silt loam
Silt
Sandy clay loam
Clay loam
Silty clay loam
Sandy clay
Silty clay
Clay and heavy clay
Textural
Symbol
(Italian)
K for less
than 2 % OM
K for
more
than 2 %
OM
S
SF
FS
F
FL
L
FSA
FA
FLA
AS
AL
A
0.0040
0.0066
0.0184
0.0448
0.0540
0.0830
0.0277
0.0435
0.0461
0.0198
0.0356
0.0316
0.0013
0.0053
0.0158
0.0342
0.0487
0.0790
0.0250
0.0369
0.0395
0.0184
0.0342
0.0277
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1.3 CALCULATION OF C FACTOR (file name: c)
The C Factor has been obtained from Corine 2006 with the next table.
Crop Type
Grain Corn
Silage Corn, Beans & Canola
Cereals (Spring & Winter)
Seasonal Horticultural Crops
Fruit Trees
Hay and Pasture
wood 75-100% cover
wood 45-70% cover
wood 20-400% cover
Vineyard tilled inter-row
Vineyard tilled inter-row, (natural grass in winter)
Viveyard with grassed inter-row 20%cover
Viveyard with grassed inter-row 40% cover
Viveyard with grassed inter-row 60% cover
Viveyard with grassed inter-row 80% cover
Olive grove (soil with no grass cover)
Olive grove (soil with grass cover)
Rotation of 1 year corn, 1 year grain, 2 years hay pasture
or 3 years corn, 3 years hay pasture
Rotation of 2 years corn, 4 years hay pasture
C Factor
0.4
0.5
0.35
0.5
0.1
0.02
0.0006
0.003
0.007
0.65
0.35
0.2
0.1
0.042
0.013
0.1
0.02
0.16
0.12
1.4 CALCULATION OF L FACTOR (file name: l)
First slope_length has been calculated (in meters) with SAGA GIS from the DEM.
The L factor has been calculated from slope_length with the next formula:
(slope_length * 3.2808 / 72.6) 0.5
1.5 CALCULATION OF S FACTOR (file name: s)
The slope has been calculated as % from DEM.
The S factor has been calculated from slope with the next formula:
0.065 + 0.0456*slope + 0.00654*slope2
1.6 MODELS FOR SOIL VULNERABILITY AND SENSIBILITY TO WATER
EROSION (file names: erpotentthay and erosion_thay2)
The soil vulnerability to water erosion (potential soil erosion, that is not considering the effect of land
cover) has been calculated with the next formula:
eros_t_ha_y_potential= k_layer*r_layer*l_layer*s_layer
where eros_t_ha_y_potential (file name: erpotentthay) are the t ha-1year-1 of soil eroded
potentially, that is, not considering the effect of land cover.
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The soil sensibility to water erosion (actual soil erosion, that is considering the effect of land cover)
has been calculated with the next formula:
eros_t_ha_y= c_layer*k_layer*r_layer*l_layer*s_layer
where eros_t_ha_y (file name: erosion_thay2) are the t ha-1year-1 of soil actually eroded,
that is, considering also the effect of land cover.
1.7 MODEL FOR EROSION RISK (file names: t_ha_sic and erosion_years)
To calculate the erosion risk we have evaluated the damage of soil erosion in terms of years necessary
to completely loss the soil. To that purpose we have derived from the Pedological Map of Sicily
(1:250.000 scale) a grid of the ton/ha of soils (file name: t_ha_sic). Then we have calculated the risk
with the next formula:
years_to_complete_soil_loss= t_ha/eros_t_ha_y
where years_to_complete_soil_loss (file name: erosion_years) are the years theoretically
necessary to have a complete soil loss, t_ha are the ton/ha of the Sicilian soils, eros_t_ha_y
is the actual soil erosion.
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