Since 1855 the longitudinal main-channel profiles in the LYR are concave-shape curves, and concavity values of these profiles increased slightly with the recent channel degradation.

• 河床在冲刷过程中，主槽纵比降变化不大，其纵剖面形态自1855年以来均为下凹曲线，其凹度值随河床冲刷而略有增大；