Thanks to the accurate Navier-Stokes equations solver Gerris, we simulate the impact of a single raindrop of diameter D, at terminal velocity, on water layers of different thickness h: D/10, D/5, D/3, D/2, D, 2D, in order to study pressures and shear stresses involved in raindrop erosion. Such descriptions help to understand the dynamics of the raindrop impact since the pressures and the shear stresses are involved in soil detachment and are crucial for studying soil erosion by raindrops. A self-similar approach is applied to describe the pressure and the shear stress on the soil surface and self-similar profiles are investigated for both quantities as the aspect ratio h/D varies. We find that these quantities have a specific dependence on the ratio between the drop diameter and the water layer thickness and that the scaling laws recently proposed in fluid mechanics are also applicable to raindrops.