South Sudan’s oil export road network — a set of gravel and earth corridors linking oilfields in Unity, Upper Nile, and Jonglei states to downstream processing and border infrastructure — is simultaneously exposed to two severe, structurally distinct and potentially compounding hazards: seasonal flooding driven by upper White Nile hydrology, and politically motivated conflict-related disruption ranging from ambush to deliberate infrastructure destruction. Neither hazard has been systematically quantified in engineering terms for this specific network, and their interaction — the possibility that flood damage creates convoy vulnerability windows exploited by armed actors, or that conflict denies access for flood repairs creating cascading network failure — has not previously been formally modelled. This study develops a Multi-Hazard Vulnerability Index (MHVI) for 24 road segments comprising the core oil export corridors in South Sudan, integrating: (1) a hydraulic flood exposure index derived from HEC-RAS steady-flow modelling and 30-year daily discharge records; (2) a conflict exposure index derived from 2010–2023 Armed Conflict Location and Event Data (ACLED) records spatially joined to road corridor buffers; (3) a physical road condition index from SSNRA inspection data and satellite passability monitoring; and (4) a network criticality index based on graph-theoretic connectivity analysis. The MHVI identifies three segments as Critical and seven as High Vulnerability, with the Unity oilfield access roads exhibiting the highest combined hazard exposure. A compound hazard dependence amplification factor δ = 1.82 (95 CI: 1.41–2.31) is empirically estimated from 34 documented closure events, quantifying the structural coupling between flood damage and conflict-related acc