# INCA

INCA soil erosion model requires the following land use specific model parameters (inca\_table):

**Table 33: inca\_table**

| Land Use Class | Vegetation Cover (V) | Ground Cover (CG) | Calibration Parameter (a4) | No Erosion |
| -------------- | -------------------- | ----------------- | -------------------------- | ---------- |
| **-99**        | 1                    | 2                 | 3                          | 4          |
| **1**          | 8.5                  | 0.65              | 0.7                        | 0          |
| **2**          | 5                    | 0.35              | 1.5                        | 0          |
| **3**          | 3.5                  | 0.3               | 5                          | 0          |
| **…**          | …                    |                   |                            |            |

The vegetation cover (V) is similar to the canopy cover of the other soil erosion models, but multiplied with a factor 10. The vegetation cover is determined by LAI ∙ 10 in case the vegetation module is used. The ground cover (Cg) and “no erosion” columns are similar to the ones used by MMF. The calibration parameter a4 is described below.

The soil erodibility for splash (ESP) and flow erosion (EFL) can be used for model calibration and have default values of 0.005 kg m-2 s-1 and 0.003 kg km-2 s-1.

The splash detachment scaling parameter CX1 is a constant with a value of 3 s m-1.

The model parameters a1-a6 include constants and parameters that can be used for model calibration. The constants include a2 (=0 m2 s-1), a3 (=0.15) and a5 (=0 m2 s-1). The other parameters can be used for model calibration. The calibration parameter a4 can be given as a fixed value for all model domain or be land use specific using inca\_table (Table 33).

**Table 34: Model parameters**

| Model Parameter                                | Model Variable | Unit        | Range/Default |
| ---------------------------------------------- | -------------- | ----------- | ------------- |
| **Vegetation cover**                           | V              | -           | 0-10          |
| **Ground cover**                               | Cg             | -           | 0-1           |
| **No erosion**                                 |                | -           | 0 or 1        |
| **Soil erodibility for splash erosion**        | ESP            | kg m-2 s-1  | 0.005         |
| **Soil erodibility for flow erosion**          | EFL            | kg km-2 s-1 | 0.003         |
| **Splash detachment scaling parameter**        | CX1            | s m-1       | 3             |
| **Flow erosion scaling factor**                | a1             | s m-2       | 7-15          |
| **Flow erosion direct runoff threshold**       | a2             | m2 s-1      | 0             |
| **Flow erosion non-linear coefficient**        | a3             | -           | 0.15          |
| **Transport capacity scaling factor**          | a4             | kg m-2 km-2 | 0.7-10        |
| **Transport capacity direct runoff threshold** | a5             | m2 s-1      | 0             |
| **Transport capacity non-linear coefficient**  | a6             | -           | 0.73-0.9      |
