**3.1.2 Climate**

The data of the initial model that characterized the rainfall erosivity have been conserved. Concerning the number of days when the rainfall intensity is above 10 mm, we made an average monthly counting for the 1991-2004 period starting from the network of meteorological stations presented previously. For the average monthly positive hydrological balance, we used the monthly data of hydrous budget reports used in the initial version of the SCALES model.

Monthly classes are the following. For DI10: =1; =2;=3;=4; >=5 For YPHB: <30 mm; [30-60 mm[; [60-90 mm[; [90-120 mm[; >=120 mm Those are respectively comparable with the levels of pressure 1, 2, 3, 4, 5.

## **3.1.3 From monthly data to seasonal data**

In order to estimate the soil erosion hazard at seasonal scale, we calculated, for the initial data rate of plant covering, DI10 and YPHB, the average of values of the months that characterized each season. Thus, the value relative to the spring results from the average of values obtained for March, April and May. The values of June, July and August provide the summer value ; the ones from September, October and November give the autumnal value and the ones from December, January and February are the winter value. Thus, the monthly classes presented previously are reused to estimate the seasonal levels of pressure for the initial data that showed an intra-annual variability.
