Earth Science Lab
River Erosion Sandbox / Classroom activity
Student activity · Grades 6–10 · about 15 minutes

Erosion and Deposition Activity

Goal: Use a model stream table to find out how slope, water flow and grain size control erosion and deposition.

Open the sandbox at earthsciencelab.org/tools/river-erosion/ · Connects to NGSS MS-ESS2-2, HS-ESS2-5

Open the sandbox
ClaySiltSandGravel0.0010.010.11101000.11101001000Grain size (mm)Water speed (cm/s)ErosionTransportDepositionpicked up above this linesettle out below this line
Hjulström diagram (approximate). Clay 0.002 mm, silt 0.02, fine sand 0.2, coarse sand 1, gravel 3 mm.

What to do

  1. Open the River Erosion Sandbox. Choose Fine sand and set Sediment fed in to 0.
  2. Set the slope and water flow for setup A, then drag the time slider to 10 minutes (or press Run and watch).
  3. Record the water speed at the start, the sediment eroded, the deepest cut and the delta length. Repeat for B, C and D.
  4. Answer the questions. Use the Hjulström diagram (on this sheet or in the sandbox) for questions 4 and 5.

Record your results (after 10 minutes)

SetupSpeed at start (cm/s)Eroded (cm³)Deepest cut (cm)Delta length (cm)
A: 2% slope, 2 L/min
B: 6% slope, 2 L/min
C: 2% slope, 6 L/min
D: 6% slope, 6 L/min

Extra: set up A again with 60 cm³ of sediment fed in per minute. After 10 minutes, the bed near the inlet has built up ______ cm.

Questions

  1. Which setup eroded the most sand, and which eroded the least? Use the water speeds to explain why.

  2. Compare B and C: did more slope or more water make the water faster? Which built the longer delta?

  3. Where did the sand cut from the channel end up? Why there?

  4. At 40 cm/s on the Hjulström diagram, which sediments are eroded and which are only transported?

  5. Clay grains are smaller and lighter than sand. Why does clay need faster water to be picked up?

  6. Predict, then test: will gravel build a longer or a shorter delta than fine sand in setup D? Why?

Free from Earth Science Lab · earthsciencelab.org · MS-ESS2-2: Construct an explanation, based on evidence, of how geoscience processes have changed Earth’s surface at varying time and spatial scales. HS-ESS2-5: Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.