Vegetation Components as Nature‐Based Solutions to Reduce Runoff and Soil Loss in a Brazilian Semi‐Arid Ecosystem

ABSTRACT Hydraulic roughness (log f ) is invoked as an integrator of vegetation effects on overland flow in semi‐arid catchments, yet the quantitative contribution of individual cover components remains poorly resolved. This study aimed to elucidate the mechanisms by which shrub vegetation, surface litter and tree canopy modulate runoff generation, effective infiltration and interrill detachment on Inceptisols of the Brazilian Caatinga and to establish hydraulic roughness (log f ) as a process‐anchored indicator of vegetation–overland flow coupling. Sixteen single‐event rainfall simulations (88 mm h −1 , 30 min) were applied on 1 × 2 m plots in the Jacu River watershed (north‐eastern Brazil), comparing four cover treatments ( n = 4 each), namely, shrub (T1), litter (T2), canopy only (T3) and bare soil (T4). Runoff coefficients fell from 0.700 in T4 to 0.430 in T1 and 0.380 in T2, whereas effective infiltration rose from about 20 to 42–44 mm h −1 and soil loss declined from 0.440 to 0.120–0.170 t ha −1 . Hydraulic roughness reached log f = 1.410 in T2 and 1.340 in T1 against 0.660 in T4 and was inversely associated with the runoff coefficient and soil loss and positively associated with infiltration. Canopy alone (T3) recovered only about half of the infiltration gain delivered by shrub and litter covers, indicating that surface‐contact elements rather than overhead protection govern flow attenuation. The treatment ranking was preserved under perturbations of the velocity‐correction factor and the infiltration estimate. The results support log f as a transferable, mechanism‐anchored indicator of vegetation effects on overland flow and erosion in semi‐arid drylands, conditional on the rainfall intensity and textural class tested.