We applied rainfall and tracers on two 8 m wide runoff plots to better understand runoff generation processes in pre-Alpine catchments with low permeability gleysols. The results highlight the frequent occurrence of infiltration and exfiltration of water, the importance of preferential flow, and the quick runoff response (i.e., high celerity) and transport of solutes (i.e., high velocity). These results help to understand why streams in the study region respond very quickly to rainfall.