Impacts of the Degraded Alpine Swamp Meadow on Tensile Strength of Riverbank: A Case Study of the Upper Yellow River

Abstract

In the meandering riverbank of the Upper Yellow River (UYR), the native alpine swamp meadow (AS) has continuously degenerated into an alpine meadow (AM) due to climate change and intensified grazing. Its implication on river morphology is still not well known. This study examined this effect by in situ measurings of (1) physical properties of roots and their distribution in the soil-root mixture of the upper bank layer, and (2) the tensile strength in terms of excavating tests for triggering cantilever collapses of AS and AM riverbanks. The results showed that the root number in AS was significantly greater than that in AM, though the root distribution in both was similar. Also, the average tensile strength of individual roots in AS was 31,310 kPa, while that in AM was only 16,155 kPa. For the soil-root mixture, it decreased from 67.39 to 21.96 kPa. The weakened mechanical property was mainly ascribed to the lessened root number and the simpler root structure in the soil-root mixture of AM that reduces its ability to resist the external force. These findings confirmed that healthy AS can enhance bank stability and delay the development of tensile cracks in the riverbank of the meandering rivers in the UYR.

Soil–Water Conservation, Erosion and Landslide

“…Chen, Guo, and Wang [16] compared farmland with revegetated gullies and demonstrated that revegetating gullies could lower soil erodibility by 31-78% and could further improve critical shear stress by up to four times, and stable conditions were possible in approximately 18 years. The importance of riparian vegetation in stabilizing river banks is illustrated by Zhu et al [17]. The authors show that healthy native alpine swamp can enhance riverbank stability and could further delay the development of tensile cracks.…”