Riverbank Collapse Causes and Characteristics of the Upper Yellow River with Wide Valley in Desert Area

Riverbed rise and suspended river occurred in the wide valley desert reach of the upper Yellow River. Riverbank collapse is one of the main sediment sources, which causes much attention. To understand riverbank collapse mechanism and evaluate sediment quantity brought by riverbank collapse, riverbank collapse causes and characteristics were analyzed in this study. Based on the particle size gradation tests, the study reaches were divided into two kinds. Type I was composed of sand from the surrounding desert while type II was made up of silt from sediment. Riverbank collapse causes were displayed from the view of both soil mechanism and hydraulics with respect to the two kinds of riverbanks. The factors of soil mechanism included physical properties (e.g. cohesion and friction) and morphology characteristics (e.g. height and slope). Water table, river stage and velocity were the main hydraulic factors. Wuhai and Dengkou were selected as the representative observation sites corresponding to the two kinds of riverbanks. By field observation and indoor experiments, their physical features and morphology characteristics related to riverbank collapse causes were demonstrated.