Sediment Transport & River Erosion Lab
Adjust slope, discharge, channel width and grain size and use the real Hjulström curve to predict whether a river erodes, transports or deposits sediment — then add a dam and watch downstream effects.
How to use: adjust slope, discharge and channel width to change flow velocity, and place a dam to see trapped sediment. Watch the Hjulström curve tab to see where each grain size erodes, transports or deposits, then try the Challenge tab.
Challenge: transport sand but deposit gravel
The Hjulström curve shows that fine sand erodes and transports at fairly low velocities, but gravel needs high velocity to erode and drops out (deposits) once velocity falls only a little. Find a flow velocity where sand keeps moving (transport or erosion) while gravel is deposited.
Challenge 2: hit the transport window exactly
Sand transports (moves along without eroding or fully settling) only in a narrow window, between its deposition and erosion thresholds. Tune the sliders so sand's state is exactly Transporting.
About the Sediment Transport & River Erosion Lab
Free sediment transport & river erosion lab. Adjust slope, discharge, channel width and grain size and use the real Hjulström curve to predict whether a river erodes, transports or deposits sediment — then add a dam and watch downstream effects. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for geology, the sediment transport & river erosion lab runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Adjust slope, discharge, channel width and grain size and use the real Hjulström curve to predict whether a river erodes, transports or deposits sediment — then add a dam and watch downstream effects. Use it to explore geology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Sediment Transport & River Erosion Lab
- Use the controls to change Channel slope, Discharge (flow), Channel width, Rainfall. The simulation reacts instantly.
- Press "Place a dam", "Remove dam", "Reset to defaults", "📄 Lab Report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Find a flow velocity where sand transports but gravel deposits (the challenge).
- Place a dam and watch the channel change upstream and downstream.
- Raise the slope and discharge together and see the meander pattern strengthen.
- Compare a wide, slow channel to a narrow, fast one at the same discharge.
Key ideas you can learn
- The Hjulström curve shows the flow velocity needed to erode, transport or deposit a given grain size.
- Fine sand is actually easier to erode than clay, because clay particles are cohesive and stick together.
- Gravel needs high velocity to erode but drops out (deposits) quickly once velocity falls.
- A dam traps sediment upstream and releases sediment-starved, erosive clear water downstream.
Where this is used in the real world
River engineers use the Hjulström curve and dam-effect reasoning to design channels, protect bridges and predict where a dam will cause downstream riverbed erosion.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why is fine sand the easiest sediment to erode?
Coarser grains like gravel need high velocity because they are heavy; very fine grains like clay resist erosion because their particles are cohesive and stick together, so sand sits at the easiest-to-erode minimum.
Why do dams cause downstream erosion?
The reservoir traps sediment, so the river downstream still has erosive energy but nothing left to deposit, and it starts cutting into its own banks and bed.
Is the Sediment Transport & River Erosion Lab free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Sediment Transport & River Erosion Lab work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.