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Malti🏞️ River Delta Formation Simulation
Interactive river delta simulation — watch sediment build a delta as distributary channels branch, avulse, and wave energy reshapes the coastline from birdsfoot to arcuate.
Watch a river build land grain by grain as it meets the sea. This simulation tracks sediment deposition on a live elevation grid, routes an active channel that branches and avulses as it silts up, and lets a wave/tidal energy control reshape the growing delta from a pointed, river-dominated birdsfoot into a smooth, wave-dominated arc — the same spectrum of shapes found from the Mississippi to the Nile to the Ganges-Brahmaputra.
🔬 What It Demonstrates
Deltas form where a river's carrying capacity collapses as it enters standing water, and where that river's channels branch, migrate and periodically avulse to distribute sediment across a widening front rather than building a single endless spit.
🎮 How to Use
Raise sediment discharge to accelerate land-building, and slide wave/tidal energy from 0% toward 100% to watch the same river reshape its coastline from a jagged birdsfoot into a rounded arc. Use time speed to fast-forward through centuries of growth, and Reset to start from open water.
💡 Did You Know?
A single large river can add several square kilometres of new land to a delta in a single year during major flood seasons, then abandon that lobe entirely within decades once avulsion sends its main flow somewhere else along the coast.
About the River Delta Simulation
This simulation tracks sediment deposition on a live two-dimensional elevation grid representing the seabed where a river meets standing water. Sediment particles are released from the river mouth along an active distributary channel; their chance of settling out rises the further they drift from the channel's centerline and the more the local flow has slowed, mirroring how real rivers lose their sediment-carrying capacity as they spread into open water. Once enough sediment piles up in one place, that cell crosses the surface and becomes land, blocking further flow and forcing the channel to route around it — the same feedback that produces the branching, fan-shaped networks of distributary channels seen in every real delta.
When the cells at a channel's own mouth become too silted up to carry more flow, the simulation triggers an avulsion: the river breaches its bank upstream and jumps to a new heading, sometimes splitting into an additional branch. This is exactly how real deltas like the Mississippi build outward in a sequence of abandoned and active lobes over centuries. The wave/tidal energy control adds a second, competing process — coastal reworking — that redistributes newly deposited sediment sideways along the shoreline each tick, smoothing a river-dominated, finger-like birdsfoot delta into the rounder, wave-dominated arc shapes seen where ocean energy is stronger than river sediment supply.
Frequently Asked Questions
What does this simulation show?
It models a river entering standing water and depositing sediment where its current slows, building a delta on a live grid over simulated years. You can watch distributary channels branch, silt up, and jump to new paths, while a wave/tidal energy control determines whether the resulting delta stays pointed or gets smoothed into a curved coastline.
What is a river delta and how does it form?
A delta is a landform built from sediment that a river deposits as it enters a standing body of water, such as a sea or lake, and loses the energy needed to keep carrying that sediment. Over enough time, repeated deposition raises the seabed above water level, creating new land that keeps growing outward as long as sediment supply continues.
What is avulsion and why does the channel keep moving?
Avulsion is the sudden abandonment of a river channel in favor of a new path, usually triggered when the channel's own deposits raise its bed and banks so much that flowing elsewhere becomes easier than continuing to push through the silted-up mouth. It is the main mechanism by which deltas grow into fan-shaped networks rather than a single ever-lengthening spit.
What's the difference between river-dominated and wave-dominated deltas?
In a river-dominated delta, sediment supply from the river outpaces the ocean's ability to rework it, so deposits pile up in narrow, finger-like lobes right where the channels enter the sea — the Mississippi's "birdsfoot" delta is the classic example. In a wave-dominated delta, strong waves redistribute sediment sideways along the coast faster than the river can pile it up, smoothing the shoreline into a rounded, arcuate shape, as seen at the Nile and the Ebro. Tide-dominated deltas, like the Ganges-Brahmaputra, are instead carved by strong daily tidal currents into long, branching tidal channels.
What do the controls do?
Sediment discharge sets how many sediment particles the river injects into the simulation each tick, controlling how fast the delta grows. Wave/tidal energy controls how much freshly deposited sediment gets redistributed sideways along the coast every tick, shifting the delta's shape from birdsfoot toward arcuate. Time speed sets how many internal simulation ticks run per animation frame, fast-forwarding through more simulated years per second. Reset clears the grid back to open water and restarts the years counter from zero.
What are distributary channels?
Distributary channels are the branching waterways a river splits into as it crosses its own delta, each one carrying part of the total flow and sediment load toward the sea. They form and re-form through repeated avulsion events, and the resulting branching pattern is what gives deltas their characteristic fan or "bird's foot" outlines when viewed from above.
How is the "years elapsed" figure calculated?
Each internal simulation tick advances the clock by a small, fixed fraction of a year, so the total is simply the number of ticks that have run since the last reset multiplied by that fraction. It is an arbitrary but internally consistent timescale meant to convey how many "simulated years" of sediment accumulation you're looking at, not a real-time clock.
Is this a physically exact model of delta formation?
It captures the core qualitative processes — velocity decay away from the channel, distance-dependent deposition, land-blocking flow, avulsion, and wave reworking — using simplified rules rather than full fluid-dynamics equations. Real deltas are also shaped by subsidence, sea-level change, vegetation, and human interventions like dams and levees, none of which this simulation attempts to reproduce.
A river meeting still water drops coarse sediment first and fine sediment further out, building channels that shift into birdfoot or cuspate deltas.
3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install