Runoff and erosion in the Black Marls of the French Alps: Observations and measurements at the plot scale

The behaviour was very different during natural rainfall events, in particular summer storms: even if the mean rainfall intensity was lower than 60 mm h− 1 in 30 min, short periods of high intensity (more than 100 mm h− 1 in 5 min) revealed substantial erosion activity: more than 700 g m− 2 on all the plots for a rainfall event of 54 mm in 3 h and more than 600 g m− 2 for an event producing 26 mm. However, the runoff coefficients were on the same order as those of the last experiment under high-intensity conditions (32-55%). The rainfall intensity over the short duration and the kinetic energy of the raindrops were the main factors influencing particle detachment and movement.