riveralignment

River alignment refers to the horizontal course of a river channel as it traverses its valley. It encompasses the planform geometry—the layout of the channel when viewed from above—and the overall orientation of the river relative to the landscape. Alignment is dynamic, changing as erosion, deposition, and tectonic or climatic processes alter gradient, base level, and sediment supply.

Natural influences on alignment include bedrock lithology, valley slope, base level, tectonic uplift, and climate. In environments with cohesive sediments and gentle gradients, rivers tend to develop meandering courses with sinuosity greater than about 1.5. In areas with high sediment load or variable discharge, braided channels may form, featuring multiple converging and diverging strands. Lateral migration can shift channel positions across floodplains over years to centuries, while avulsion can create new channels when the water surface seeks a shorter or steeper path.

Channel planforms are commonly described as straight, meandering, or braided. Straight channels are relatively rare and often limited to confined valleys; meandering channels follow sinuous paths and create cutbanks and point bars; braided channels consist of two or more interwoven channels separated by sand or gravel bars.

Human activities, such as channelization, dam construction, bank stabilization, gravel extraction, and urban development, can alter alignment by promoting incision or aggradation, diverting flow, or locking channels in place.

Alignment is studied with maps, aerial photographs, lidar, and GIS, supported by hydrological and geomorphological models. Understanding river alignment informs flood risk management, habitat connectivity, sediment transport, and river navigation.