Tracing river dynamics: Multi-temporal planform evolution and morphological change analyses in a meandering reach using high-resolution satellite imagery and UAV data

Abstract

This study investigates the spatiotemporal dynamics of meander evolution and morphological change along a 7 km reach of the Atrak River's Chat–Gonbad corridor in northern Iran. Addressing critical gaps in the high-resolution monitoring of river morphodynamics, the research seeks to answer the following: (Ahmed et al., 2019) Which morphometric parameters are most influential in reflecting meander instability? (Amissah et al., 2019) How do extreme hydrological events, particularly the 2019 flood, govern the magnitude and spatial distribution of channel adjustment? (Annayat & Sil, 2020) Can dynamic mapping be used to reliably distinguish stable from unstable reaches to guide future management? A novel dataset of submeter satellite imagery (QuickBird, SuperView, Pleiades) and unmanned aerial vehicle (UAV)-derived orthophotos was compiled for four time points (2005, preflood 2019, postflood 2019, 2024). For 21 meander bends, key morphometric indices—amplitude, channel width, radius of curvature and sinuosity—were extracted. Statistical analyses (ANOVA, Friedman, Wilcoxon tests) revealed that all major parameters underwent significant temporal variability: amplitude varied most strongly (ANOVA F = 8.89, p = 0.00007), while channel width (Friedman X² = 18.6, p = 0.00033) and radius of curvature (X² = 21.52, p = 0.00008) showed marked sensitivity to high-magnitude events. Cumulative bank erosion during the 2019 flood peaked at 18 383.8 m²—nearly an order of magnitude higher than in the 2005–2019 preflood interval. Notably, critical reaches (especially 15, 17 and 19) exhibited the most persistent instability. Positive Kendall's tau and Sen's slope values in 14 of 19 reaches, although not statistically significant, suggest a general tendency towards increasing sinuosity, supporting the interpretation that sinuosity is a relatively inertial planform metric that reflects cumulative long-term meander adjustment rather than abrupt event-scale response. The integration of remote sensing and UAV-derived DEMs enabled highly detailed, actionable mapping of channel change. These findings offer crucial guidance for developing adaptive, reach-specific monitoring and intervention strategies. Ongoing research should focus on linking morphodynamic metrics to hydrological drivers to further support river corridor resilience and risk mitigation initiatives.