River Sandbox

Live river simulation · runs in your browser

See how rivers really flow.

River Sandbox simulates water over real terrain, live, on your graphics card. Watch eddies spin up behind boulders, currents bend around islands and backwater pool above a dam, then change the river and see what the water does.

Start with a lesson Open River Sandbox

Checking whether this browser can run River Sandbox…

The Wenatchee River pouring over Tumwater Dam, with white water in the canyon below
Tumwater Dam on the Wenatchee River, Washington: the first lesson.

Three ways in

  • A rock and a spur in a small river, with white wakes where the current splits around them, from the Eddies lesson

    Learn

    Guided lessons

    Short lessons on real places: the pool above Tumwater Dam, the eddy behind a rock, riffles and pools, a confluence. Each step points the camera at what to watch.

    Browse the lessons
  • Icicle Creek meeting the Wenatchee River near Leavenworth, Washington

    Explore

    Real US rivers

    Open one of a dozen river sections, from the Royal Gorge to St. Anthony Falls, or pick any spot on the map. River Sandbox loads lidar elevation, mapped river lines and gauge flows for it.

    Choose a river
  • Water running through the Rock garden starting map

    Play

    Sandbox

    Start from a valley, a canyon, a reservoir or a waterfall and make it your own: sculpt the banks, place boulders, build dams and change the flow.

    Pick a starting map

How it works

  1. Pick a place

    A lesson, a real river or a starting map.

  2. Let it fill

    Water runs in from the sources until the flow settles.

  3. Change something

    Sculpt the banks, drop a boulder, build a dam or turn up the flow.

  4. Watch the water answer

    The flow map and drifting leaves show where it speeds up, slows down and turns back.

Built on public data

In the United States, maps use USGS 3DEP lidar elevation, National Hydrography Dataset river lines, NLCD land cover, NAIP aerial imagery and USGS stream gauges. Elsewhere, global Terrain Tiles fill in.

  • 3DEPLidar elevation
  • NHDRiver lines
  • NLCDLand cover
  • NAIPAerial imagery
  • USGSStream gauges

No account needed

Everything works without signing in, and your scenes save in this browser. Sign in with an email link, a passkey, Google or GitHub to keep scenes in the cloud, share them with a link and publish them to the gallery.

Sign in

What you need

River Sandbox runs on WebGPU. A current Chrome or Edge on a desktop or laptop with an up-to-date graphics driver works best; Safari and Firefox support WebGPU on some platforms. Phones and tablets with WebGPU work too, with touch controls.