## 1 Introduction  
Channel lateral migration is a morphodynamic adjustment that has been extensively documented in various rivers worldwide [1; 2; 3; 4; 5]. Lateral migration plays a crucial role in the functioning of aquatic and riverine ecosystems, and reduced lateral migration usually leads to a decrease in habitat quality [6; 7; 8]. Therefore, the restoration and preservation of river environments usually require a mobile channel [9; 10]. On the other hand, severe channel lateral migration may threaten the safety of flood control structures and human property, a topic that has attracted great attention from scientists in the context of river engineering and fluvial management [11; 12; 13; 14]. Lateral migration in alluvial rivers generally covers channel width adjustments, thalweg migration, shifting of the main channel, and meander migration. The thalweg is the line of lowest bed elevation within the watercourse [2]. Large-scale shifting of the main channel can lead to severe thalweg migration, and thalweg migration rates usually exceed the magnitude of the main channel shifting [15]. Various methods have been used to determine the magnitude of channel lateral migration in recent years, including analysis of measured cross-sectional profiles, remote sensing techniques, and mathematical models [4; 16; 17; 18; 19]. For example, [PERSON] et al. [16] investigated the changes in bankfull width in a braided reach after the operation of a large reservoir based on annual measured cross-sectional profiles, which indicated that bankfull width increased greatly owing to severe bank erosion. [PERSON] et al. (2018) analyzed the characteristics of channel width, radius of curvature, and sinuosity index using Remote Sense (RS) and Geographic Information System (GIS) in the Khowai River, with the relationship between channel migration and land use being discovered. [PERSON] et al. (2019) developed a morphological mathematical model to simulate the processes of bank failure and bed deformation, and the results showed that the effect of secondary flow played an important part in channel migration. Analysis of measured cross-sectional profiles can accurately show the variations in channel migration, which is a common method to investigate fluvial processes of alluvial rivers. Remote sensing techniques can acquire a wide range of data, but the precision is often affected by weather, such as clouds and snow. Mathematical models can simulate the processes of channel width changes and thalweg migration, but it usually needs detailed information including bed material composition and bank soil properties. Fluvial processes in alluvial rivers are generally influenced by various boundary conditions, including upstream boundary conditions, downstream boundary conditions, and other boundary conditions (2018, 2019). The upstream boundary conditions usually refer to the incoming flow and sediment regime, which are considered to be the main factors influencing channel evolution. Some studies have been conducted to investigate the effect of upstream boundary conditions on channel lateral migration (2018, 2019, 2020, 2021). For example, [PERSON] et al. (2019) investigated the lateral movement of the Rio Grande in New Mexico and found that channel migration rates primarily increased with an increase in flow energy based on statistical analysis. [PERSON] et al. (2018) investigated the variation in thalweg migration intensity in a braided reach of the Lower Yellow River in 1986-2015 and established a relation between thalweg migration intensity and the previous 4-year average fluvial erosion intensity. [PERSON] et al. (2019) determined the migration rates of the main channel in a wandering reach and found that fluvial factors were the key factors influencing the migration rates. The downstream boundary conditions generally refer to changes in the local base level, which is regarded as an imaginary horizontal level or surface where channel erosion proceeds (2018).