# 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 29: 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 30 and Table 31, respectively.

**Table 30: 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 31: 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 32: 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           |
