Runoff and sediment processes at basin scale by integrated hydro-sediment-morphodynamic modelling

The Tuotuo River basin, the primary headwater region of the Yangtze River on the Tibetan Plateau. The intrinsic coupling of runoff and sediment processes is a primary driver of global geomorphic dynamics. Accelerating climate change is profoundly altering these processes, posing significant challenges for river basin management. However, existing basin-scale models often neglect or oversimplify morphodynamic processes within channel networks. To address this gap, we introduce an integrated, basin-scale hydro-sediment-morphodynamic modeling framework that explicitly couples overland runoff and hillslope erosion with in-channel hydrodynamic and morphological processes. We apply this framework to the Tuotuo River basin to elucidate the spatiotemporal evolution of runoff and sediment processes during 1985–2018 and project future changes under three CMIP6 climate scenarios (SSP1–2.6, SSP2–4.5, and SSP5–8.5) from 2019 to 2100. It is shown that rainfall contributed 58 % of the total runoff, followed by base flow (30 %), snowmelt (7 %), and glacier melt (5 %) during 1985–2018. Runoff and sediment flux are projected to substantially increase by the 2060 s, with magnitudes rising by approximately 140–210 % and 150–270 %, respectively. Thereafter, runoff and sediment flux decrease under SSP1–2.6, stabilize under SSP2–4.5, but sharply increase under SSP5–8.5. Significant spatial heterogeneity in hillslope erosion and erosion-prone and depositional sections in the channel network are identified. This modeling framework provides a general tool for basin-scale hydro-sediment-morphodynamic processes, offering critical insights for regional water resource management and ecological conservation under changing climate. • An integrated basin-scale hydro-sediment-morphodynamic framework is proposed. • Erosion-prone and depositional regions are identified in the Tuotuo River basin. • Sediment erosion exhibits significantly greater spatial variability than runoff. • Runoff and sediment flux follow divergent trajectories across climate scenarios. • Carbon emission control is crucial for regulating runoff and sediment flux.