The self-reinforcing curve of river erosion
Rivers naturally find the path of least resistance, but the path itself amplifies curvature once started. When water rounds a bend, centrifugal force pushes it toward the outer bank, creating faster flow and stronger erosion. Sediment stripped from the outside pools on the inside, building sand and gravel bars. This asymmetry locks in the curve and forces the river to bend even more sharply on the next cycle.
Over decades and centuries, these feedback loops compound. A gentle bend becomes exaggerated, then dramatic. The river migrates laterally downslope, consuming farmland or building new land on the inside of each curve simultaneously.
Meanders at landscape scale
Mature river systems display signature S-curves and switchbacks visible from space. The Okavango, Amazon, and Mississippi all show extreme meanders because they flow through very flat terrain where lateral movement is energetically easier than cutting deeper. Faster rivers in steep terrain have little lateral room and wander less.
Oxbow lakes form when a meander becomes so pronounced that the river eventually cuts through the narrow neck of land, abandoning the long curve and isolating it from the main flow. These features mark the temporary waypoints of river migration and are common in floodplains throughout the world.