The research of River Morphology transition and Sediment variation: Shule River, Northwest of China

The data acquisition in this study is mainly divided into two parts: indoor statistics and field measurements to obtain. In the indoor work, satellite image data and radar digital elevation data were primarily used to measure and count the river width (Fig.1c), sinuosity, gradient, and elevation every 500m along the top of the Shule River downward (Tab.1). The river width was calculated as the distance between the outer banks, measured at a 90° angle to the river axis, including the channel bar and point bar (Mcglue et al., 2016). The classification of river morphology is mainly based on the size of sinuosity (Rust, 1978). The sinuosity greater than 1.5 is defined as a meandering river, and less than 1.5 is defined as a braided river (Fig.1c). The river gradient is counted for every two adjacent measurement points. According to the above measurement criteria, there are 237 river morphology data within the alluvial fan of the Shule River (Tab.1).

In the field measurement process, due to the limited accuracy of satellite images in portraying river morphology. We also use UAV aerial photography to refine further the river's morphological characteristics based on satellite images, which mainly included the channel bar and point bar description. Under the guidance of sedimentological theory, we measured and sampled the gravel in the modern riverbed of Shule River (Fig.2). By measuring the grain size and orientation parameters of gravel(Fig.2a), we research the refinement characteristics of sediments from the apex to the toe (Folk, 1954). Among them, gravel grain size and orientation were measured by the quantitative characterization method of gravel orientation proposed by Huang YuanGuang et al. (Fig.2a, b), and grain size was determined by the long flat axis of gravels (Huang et al., 2018), gravel orientation was measured by the rose diagram of the relative apparent dip (Fig.2b) (Huang et al., 2018; Tao et al., 2018). A total of five gravel statistical points were included within the alluvial fan of the Shule River, and a total of 1862 gravel grain size parameters were measured (Tab.2). We also use the hand-hold X-ray fluorescence spectrometer to measure the element characteristics of each sampling point (Fig.2c, d; Tab.3), which uses intelligent one-button testing and intelligent judgment functions for elements between atomic numbers 12-92 (Mg-U) (Fig.2e; Tab.3).