 This study examined how soil moisture affects the threshold runoff response in a small headwater catchment in the Italian Alps. It found that a sharp threshold exists in the relationship between soil moisture and runoff coefficients, streamflow, and hill slope average depth to water table. During dry periods, low runoff ratios were likely due to the riparian zone being close to saturation. During wet periods, however, subsurface flow was activated on hill slopes, resulting in a major contribution to runoff. Additionally, antecedent wetness conditions controlled the catchment's response time. During dry periods, streamflow reacted and peaked prior to hill slope soil moisture, while during wet conditions the opposite occurred. The study also found that small storms during dry conditions produced low storm flow amounts, likely due to overland flow from the riparian zone, while larger storms during wet conditions resulted in higher storm flow values. This article was authored by D. Penna, H. J. Tromp van Mierveld, Agobi, and others. We are article.tv, links in the description below.