<p>Hydraulic implications occur when rainfall and overland flow move across the vegetative structure of the Caatinga, the shrubland native to Brazil’s semi-arid region, which is a climate change hotspot. Can the Caatinga structure’s effects on rain interception, along with water retention caused by hydraulic resistance, significantly increase water infiltration? How can overland flow at low Reynolds numbers be affected? Twelve simulated rain events were conducted in a Brazilian semi-arid watershed, focusing on these questions in a degraded Caatinga area also used for growing semi-arid crops. The entire Caatinga vegetation and litter reduced flow velocity by 55.24% and 60.55%, respectively, and increased hydraulic resistance by 68.64% and 61.18%, respectively, compared to bare soil conditions. Hydraulic resistance was governed by the Froude number, as shown by a very good exponential decay function with a very high coefficient of determination (R² = 0.9902). Caatinga’s structural vegetative elements, such as litter (fallen leaves on the soil surface), and the entire Caatinga structure increase hydraulic resistance, providing an efficient environmental protection against overland flow. Therefore, even under the stress conditions of the dry season, Caatinga, as part of the semi-arid ecosystem, remains alive and ecologically active, responding hydraulically to overland flow.</p>