🏞️ River Meander Lab

A free channel migrates by the Ikeda–Parker–Sawai law: banks erode on the outside of a bend and deposit on the inside. Raise discharge and the bends fatten; raise cohesion and they freeze. When a neck thins enough the river cuts off and leaves an oxbow lake.

Watch bends grow, migrate downstream, and cut off.
The physics

Lateral migration ζ̇ = E · Ū · H · C, where C is centreline curvature, Ū near-bank excess velocity, H bank height and E an erodibility that falls with cohesion. Downstream advection of curvature (the “skew”) is why real meanders lean. Cutoff fires when two non-adjacent centreline points close within a channel width — the abandoned loop becomes an oxbow that slowly silts up.