MUSLE

The optional K-factor map (soil erodibility) can be provided here. The Wischmeier et al. (1971) formulations are used (see section 2.8) when this is left empty. In that case, a sand, clay and organic matter map should be provided in the PEDOTRANSFER section of the config file (even when the pedotransferfunctions are not used, i.e. if PedotransferFLAG = 0).

The P-factor map indicates the support practice factor, which indicates how conservation measures reduce soil erosion. While other model parameters may also be used to indicate soil conservation, such as the C-factor, this factor is often considered to be 1.

A look-up table needs to be defined for the land use specific model parameters. The user needs to provide a PCRaster table file (*.tbl), where each row represents a landuse class. The following data need to be provided:

Table 12: musle_table

Land use class	C-factor	Retardance coefficient
-99	1	2
1	0.05	0.1
2	0.4	0.4
3	0.2	0.8
…	…	…

The values for C-factor and retardance coefficient can be obtained from several sources. Successful applications with the MUSLE soil erosion model were obtained with the C-factor and retardance coefficient values obtained from Table 8 and Table 9, respectively.

Table 13: C-factor values for different land use classes (de Vente et al., 2009).

Land use classes	C-factor
Urban areas	0
Non-irrigated arable land	0.44
Irrigated land	0.25
Rice fields	0.05
Orchards	0.35
Fruit tree plantations	0.30
Heterogeneous agricultural areas	0.30
Deciduous/evergreen forest	0.002
Coniferous forest	0.004
Mixed forest	0.003
Natural grassland	0.08
Shrubs and transitional woodland / Matorral	0.03
Bare surfaces above 1000 m elevation	0.12
Water surfaces	0

Table 14: Retardance coefficient values for different terrains (Roussel et al., 2005).

Generalized terrain description	Dimensionless retardance coefficient (N)
Pavement	0.02
Smooth, bare, packed soil	0.1
Poor grass, cultivated row crops, or moderately rough packed surfaces	0.2
Pasture, average grass	0.4
Deciduous forest	0.6
Dense grass, coniferous forest, or deciduous forest with deep litter	0.8

Table 15: Range for different model parameters

Model parameter	Model variable	Unit	Range/default
Soil erodibility factor	K	kg h MJ-1 mm-1	0.02-0.69
Erosion control practice factor	P	-	0-1
Crop and management factor	C	-	0-1
Retardance coefficient	N	-	0-1