# 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           |
