Understanding rainfall-driven hydrodynamic variations is critical for elucidating sediment transport patterns and connectivity on sloping farmlands, yet quantifying the distribution mechanisms of sediment fractions modulated by tillage-induced microtopography is still unclear. This study investigated the dynamics of in-situ disturbed sediments (S-D), translocated sediments (S-H), sediment loss (S-L) across flatting cultivation (T-FC), horizontal cultivation (T-HC), artificial digging (T-AD), and hoeing cultivation (T-HE), under six simulated rainfall duration (RD). Sheet flow surface velocity (V-S) stabilized at 0.32, 0.32, 0.30, and 0.24 m/s for T-FC, T-HE, T-AD, and T-HC, respectively, under simulated rainfall. Correspondingly, loss velocity (V-L) plateaued at 0.32, 0.32, 0.31 and 0 m/s. Correction factor alpha transitioned from alpha< 1 to alpha> 1 after runoff initiation. S-L was predominantly generated at 5, 10, and 15 min rainfall for T-FC, T-HE and T-AD. No S-L detected under T-HC. S-D were illustrated by T-HC ([10.6, 43.2] g/min), followed by T-AD ([10.1, 43.3] g/min), T-HE ([8.2, 43.2] g/min), and T-FC ([7.3, 42.9] g/min). S-H demonstrated reductions of 42%, 56%, and 79% under T-HE, T-AD and T-HC, respectively, with increasing rainfall duration. Loss Proportion to Translocated Sediment (R-SL(y)), representing the proportion of sediment loss from slope on translocated sediments, increased and stabilized under T-HE (67%) and T-AD (38%) with the extension of rainfall duration. Loss Proportion to Disturbed Sediment (R-SL), exhibiting proportion of sediment loss on in-situ disturbed sediments from the slope, under T-FC were superior than T-HE (1%), T-AD (2%) and T-HC (3%). Random Forest Analysis confirmed that S-D was significantly controlled by rainfall simulation and sheet flow feature, compared to S-L primarily governed by hydrodynamics. S-H showed significant response to the synergistic effects of microtopographic spatial variation. Structural Equation Model elucidated that tillage-induced microtopography modulated sheet flow hydrodynamics mediated by rainfall, which exerted effects on sediment distribution, verified by RMSEA, CFI, and R-2. This study offers a comprehensive framework for understanding the coupled influence of rainfall-driven hydrodynamics and microtopography on sediment connectivity, providing valuable insights to refine erosion modeling and optimize tillage-based soil conservation strategies on loess sloping farmlands.