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🌊 River Meanders

Watch a straight river spontaneously curve into meanders as curvature-driven erosion sculpts banks, then neck cutoffs sever loops into oxbow lakes.

Geology & Earth Science3DModerate60 FPS💧 Water 🌍 Earth

About this simulation

This model represents a river as a chain of nodes, computes signed curvature at each point from centred tangent differences, and migrates every node perpendicular to the flow by an amount proportional to a slightly downstream-lagged curvature signal — the same core mechanism believed to drive real bank erosion and point-bar deposition. The polyline is continually resampled to even spacing, and whenever two non-adjacent points drift within the cutoff threshold, the loop between them is spliced out and stored as a new oxbow lake.

🔬 What it shows

How a straight channel spontaneously develops sinuous bends purely from curvature-driven bank migration, and how those bends inevitably tighten until a "neck cutoff" severs a loop, leaving it stranded as a crescent-shaped oxbow lake beside the newly straightened river.

🎮 How to use

Choose a Preset (Laminar/Straight to Braided-ish), or tune Erosion rate, Cutoff threshold, Perturbation amplitude, and River width directly; pick Flow direction, toggle Show palaeo-channels to see faint historical channel positions, and use Pause/Reset or Generate new river to restart with a fresh random seed.

💡 Did you know?

Real oxbow lakes can persist for centuries after cutoff, since the abandoned channel is quickly plugged with sediment at both ends — the Mississippi and Amazon river floodplains are dotted with hundreds of them, each marking where the main channel used to flow.

Frequently asked questions

Why do straight rivers turn into meanders on their own?

Any tiny initial bend creates a small curvature, which slightly speeds up flow (and erosion) on the outer bank while slowing it (and depositing sediment) on the inner bank; this asymmetric erosion pushes the bend outward and downstream, amplifying the curve until it becomes a full meander loop.

What causes an oxbow lake to form?

As a meander loop grows, its neck — the narrow strip of land separating two nearby parts of the same river — thins until the river breaks through it during a flood, taking the new, shorter path and abandoning the old loop, which becomes a curved, cut-off oxbow lake.

What does the sinuosity statistic mean?

Sinuosity is the ratio of the actual channel length to the straight-line valley distance; a value near 1.0 means a nearly straight channel, while values above roughly 1.5 indicate a strongly meandering river.

Why do point bars form on the inside of bends?

Water flows slower along the inside of a curve than the outside, so it can no longer carry as much sediment, causing sand and gravel to drop out and build up a point bar, while the faster outer-bank flow instead erodes a cut bank.

What do the faint palaeo-channels represent?

They are periodic snapshots of the river's centreline from earlier in the simulation, showing how the channel's position has drifted and evolved over time — a simplified analogue of the abandoned channel scars geologists find preserved in real floodplain sediments.

⚙ Under the hood

Curvature-driven erosion turns a slight wiggle into deep meanders, until necks pinch off into oxbow lakes. A floodplain of palaeo-channels fills in as the river dances across the plain.

Canvas 2DGeomorphologyErosionMeanderOxbow Lake

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install