Agricultural terrace abandonment is accelerating on the loess plateau, yet the conservation function of terraces during this transitional period remains poorly quantified. Here, abandonment is defined as the first year without maintenance, during which natural vegetation recovers while terrace geometry remains largely intact. Rainfall simulation experiments and the Terraced Nutrient Transport (TNT) model were used to quantify runoff, soil loss, and total nitrogen (TN) and total phosphorus (TP) export from six surface configurations: a bare erosional benchmark (EB), a vegetated non-terraced slope (VNS), and four terrace designs under first-year post-abandonment conditions (fish-scale pits, FSPs; zig terrace, ZTr; level bench terrace, LBTr; and ditch terrace, DTr). Rainfall simulations were conducted at 60-150 mm/h under approximately 90% vegetation cover, and the calibrated model was extended to 30-180 mm/h and 30%-90% cover. Terrace geometry strongly controlled event-scale responses: LBTr achieved the highest runoff reduction with a failure threshold of 120.2 mm/h, 7%-10% higher than other terraces, followed by ZTr and DTr, whereas FSPs and VNS were less effective under intense rainfall. TN exports were strongly associated with runoff (rho = 0.91), while TP exports were more closely related to sediment yield (rho = 0.72). TNT reproduced observed runoff, sediment, TN, and TP responses with high accuracy (runoff NSE = 0.99; sediment R 2 = 0.98; TN/TP R 2 = 0.93/0.93). Overall, structurally intact terraces retained substantial runoff, erosion, and nutrient-buffering function during the first year after abandonment, especially LBTr, ZTr, and DTr. Our results thus capture the early post-abandonment phase as a distinct period of functional resilience, during which terrace geometry and vegetation recovery jointly sustain water and soil conservation before the onset of longer-term geomorphic degradation.