21
where P is the annual precipitation (mm), and p i is the monthly rainfall.
In this study, the rainfall erosivity has been determined using the average annual
precipitation (Eqs. 3.5 and 3.6). We used these equations because they have been
widely used in similar studies (Amanambu et al. 2019; Mukanov et al. 2019; Yang
et al. 2003). The data used to derive the R factor are gridded WorldClim data of
precipitation and the GCMs.
3.2.2 Soil Erodibility Factor (K)
The K factor quantitatively determines the cohesive nature of the soil type, which
depends on the physical and chemical properties of the soil, thereby contributing to
its erodibility. These numerical indicator actions the vulnerability of soil to erosion
rainfall impacts (Renard et al. 1997; Wischmeier and Smith 1978). The main soil
properties affecting the K factor are soil texture, organic matter, soil structure, and
soil profile permeability (Uddin et al. 2016). Soil data were obtained from the Food
and Agriculture Organization, the Harmonized World Soil Data (FAO HWSD)
(Nachtergaele et al. 2010; Nachtergaele et al. 2009). The soil erodibility affects the
transportability of sediments and the vulnerability of the soil surface to erosion.
Equation (3.10), proposed by Yang et al. (2003), is expressed as follows:
K
S AN
SIL
S IL
CLA
§
©
¨
·
¹
¸
ª
¬
«
º
¼
»
®
¯
½
¾
¿
1
7 6
0 2 0 3
0 0256
1
100
.
.
. exp
.
§
©
¨
·
¹
¸
§
©
¨ ¨
·
¹
¸ ¸
SIL
OM
OM
OM
SN
S
0 3
1
0 25
3 72 2 95
1
0 75
.
.
exp .
.
.
N N
S N
§
©
¨ ¨
·
¹
¸ ¸
exp
.
.
5 51 22 9
(3.10)
where SN = 1 − SAN/100, and SAN % is the content of sand, SIL % is the content of
silt, CLA % is the content of clay, and OM is % the content of organic matter.
3.2.3 Slope Length and Steepness (LS) Factor
The topographic (LS) factor is the product of the coefficient of the slope length (L)
and steepness (S). The LS factor layer resulted from the Shuttle Radar Topography
Mission (SRTM) Digital Elevation Model (DEM) 90 m, which was obtained from
the USGS Earth Explorer database (Table 3.3). The L factor was calculated using
the methodology described by Desmet and Govers (1996).
3.2 RUSLE Model and Its Factors
where P is the annual precipitation (mm), and p i is the monthly rainfall.
In this study, the rainfall erosivity has been determined using the average annual
precipitation (Eqs. 3.5 and 3.6). We used these equations because they have been
widely used in similar studies (Amanambu et al. 2019; Mukanov et al. 2019; Yang
et al. 2003). The data used to derive the R factor are gridded WorldClim data of
precipitation and the GCMs.
3.2.2 Soil Erodibility Factor (K)
The K factor quantitatively determines the cohesive nature of the soil type, which
depends on the physical and chemical properties of the soil, thereby contributing to
its erodibility. These numerical indicator actions the vulnerability of soil to erosion
rainfall impacts (Renard et al. 1997; Wischmeier and Smith 1978). The main soil
properties affecting the K factor are soil texture, organic matter, soil structure, and
soil profile permeability (Uddin et al. 2016). Soil data were obtained from the Food
and Agriculture Organization, the Harmonized World Soil Data (FAO HWSD)
(Nachtergaele et al. 2010; Nachtergaele et al. 2009). The soil erodibility affects the
transportability of sediments and the vulnerability of the soil surface to erosion.
Equation (3.10), proposed by Yang et al. (2003), is expressed as follows:
K
S AN
SIL
S IL
CLA
§
©
¨
·
¹
¸
ª
¬
«
º
¼
»
®
¯
½
¾
¿
1
7 6
0 2 0 3
0 0256
1
100
.
.
. exp
.
§
©
¨
·
¹
¸
§
©
¨ ¨
·
¹
¸ ¸
SIL
OM
OM
OM
SN
S
0 3
1
0 25
3 72 2 95
1
0 75
.
.
exp .
.
.
N N
S N
§
©
¨ ¨
·
¹
¸ ¸
exp
.
.
5 51 22 9
(3.10)
where SN = 1 − SAN/100, and SAN % is the content of sand, SIL % is the content of
silt, CLA % is the content of clay, and OM is % the content of organic matter.
3.2.3 Slope Length and Steepness (LS) Factor
The topographic (LS) factor is the product of the coefficient of the slope length (L)
and steepness (S). The LS factor layer resulted from the Shuttle Radar Topography
Mission (SRTM) Digital Elevation Model (DEM) 90 m, which was obtained from
the USGS Earth Explorer database (Table 3.3). The L factor was calculated using
the methodology described by Desmet and Govers (1996).
3.2 RUSLE Model and Its Factors