Multi-scale analysis on the geomorphic evolution of Macao debris flow gully (NW China)

Abstract

The multiscale geomorphic evolution of the Macao debris flow gully was analyzed by integrating field surveys and quantitative analysis of morphometric parameters derived from multi-temporal 2.5 m-resolution Digital Elevation Models (DEMs) (2014–2024). At the watershed scale, temporal trends in hypsometric integral and surface incision parameters indicate an early-maturation stage with a paradoxical shift toward rejuvenation, driven by sustained incision-erosion dynamics. Channel-scale analysis reveals a systematic rightward deflection of flow trajectories, resulting in an 11 % increase in steepness on the right slope versus the left over the decade, alongside pronounced asymmetry in slope development stages (the right slope being younger than the left). Cross-sectional profiles exhibit a U-shaped morphology dominated by lateral erosion, with erosion rates on the right-slope exceeding those on the left in multiple channel segments. The persistent rightward deflection of flow trajectories and the associated amplification of right-slope erosion are consistent with Coriolis-induced centrifugal force imbalances, suggesting that rotational effects play a role in controlling lateral erosion at channel bends. These findings establish a process-form feedback framework linking morphometrics to macroscale gully evolution, offering actionable insights for enhancing erosion prediction models and optimizing terrain-specific mitigation strategies in subtropical debris flow systems.