A cusp catastrophe model for analyzing sudden channel shifting in wandering reach of the Lower Yellow River

Sudden channel shifting of wandering rivers poses significant challenges for river engineering, flood control strategies, and the security of water resources. This study proposes a novel analytical model to quantitatively assess such channel shifts based on the cusp catastrophe theory. Utilizing bathymetric data from 93 river sections collected biannually between 2015 and 2019, a comprehensive investigation of channel instability in the wandering reach of the Lower Yellow River was conducted. The results show that both lateral and longitudinal stabilities in the Huayuankou-Gaocun section were generally favorable. For the most part of the selected sections demonstrated a propensity for gradual change. Out of the 93 sections, totally 45 were identified as being susceptible to sudden channel shifts. These vulnerable sections were predominantly located in two highly active reaches—Xiaodabin-Jinglonggong and Huayuankou-Zhaolanzhuang—during the period from 2015 to 2017, excluding the 2018–2019 non-flood season. In the latter non-flood period, nearly half of the sections in the downstream reach from Jinglonggong displayed instability. Our findings are consistent closely with empirical observations from the Lower Yellow River. Additionally, the changed flow and sediment conditions in the 2015–2019 and the efficiency of guide works have significant effects on the stability of river channels.