Source characteristics and tectonic impacts on cluster debris flow hazards assessment: Evidence from the Tieba River Basin, NE Qinghai-Tibet Plateau

A clustered debris flow event triggered by extreme rainfall on August 17, 2020 in the Tieba River basin has been investigated. Unlike typical debris flow-prone areas, the absence of landslide-derived source materials was notably observed, indicating a unique genetic mechanism. To address this, a novel approach utilizing remote sensing and GIS has been proposed, focusing on the characteristics of solid material sources and structural impacts. To systematically analyze the phenomenon, debris flow gullies and key geomorphological parameters were initially identified through multi-source remote sensing and field surveys. The analysis revealed two critical genetic factors: (1) debris flow scale is derived from source characteristics, and (2) tectonic regulation of drainage patterns (tectonic impacts). Subsequently, solid material sources were classified into three groups, and the volume of loose solid materials (Vs) was estimated for each catchment. Then, the rainstorm-flood method was applied to 24 selected debris flow cases to calculate total discharge (Qₜ), which represents the debris flow scale under specific rainfall frequencies. Through regression analysis, a relationship between Qₜ and Vₛ was derived, followed by the development of predictive models for the deposition extent (width B and length L). This step not only linked sediment supply to flow dynamics but also enabled preliminary hazard zone delineation. To further incorporate tectonic influences, the angle (T) between debris flow channels and regional stress fields was quantified. By integrating Vₛ, T, and six geomorphic factors (F, Re, Ds, J, S, HI), a comprehensive hazard assessment system was constructed, bridging source materials, tectonic controls, and geomorphic conditions. Finally, an integrated model was developed using information entropy theory. The results indicate that 16 gullies have a medium to high hazard level, accounting for 66.7% of the total 24 gullies, which is largely consistent with the actual disaster situation. This study establishes a quantitative framework for debris flow hazard assessment in landslide-derived sediment-scarce, tectonically active regions, providing actionable insights for risk management.