Water Erosion Simulation


Observing water erosion: Detachment, Transportation, Deposition

Galvanized pans and a garden water bucket are used to create a small rainfall simulator.
Different soil conditions are used to demonstrate the effects of soil cover and management practices on water erosion.
Have the students form hypotheses about

  • time to intiation of runoff;
  • amount of runoff; and
  • runoff water quality (amount of sediments in water)

 

Erosion Shuffle video: Picked up and moved (opens in YouTube)

(Click images for larger photos.)


photo of pans and soil conditionsThe galvanized pans are bent slightly to give a lip on one side to direct water flow (visible in larger image), and filled with the same soil. Surface conditions effects on soil loss may be shown using turf (living grass), bare soil, and a mulch (straw. grass clippings, wood chips, etc.). A silt fence used to limit sediment loss from construction sites is simulated here.

 

rainfall simulationProp the pans to provide uniform slopes, and to catch runoff in the cups. Use glass cups for best qualitative visual results. A garden watering can is used to simulate rainfall. Three cans used simultaneously provide instant comparisons. Note time until runoff begins on each pan, and clarity of runoff (amount of sediments in the water). Slope can be varied to observe its impact on runoff and erosion.
runoff qualityObserve the difference in clarity of the runoff and amount of sediments in each cup. Vegetation on the surface greatly limits soil loss. The silt fence (or mulch) limit soil loss relative to the bare surface.

catch cupsThis closeup shows the color of the runoff, and the amount of sediments in the bottom of the cups. The cups are in the same order, so the silt fence is on the left, bare surface in the middle, and vegetated surface on the right. When the turf is fresh, the runoff is usually clear.

(Dr. Dirt often drinks the clear runoff water for effect. Kids, don't try this at home!)


 

More advanced students may do the following to integrate math and scientific research methodology:

  • Measure quantities of water added and time (for rate of precipitation).
  • Measure quantites of runoff, time to initiate runoff, and time to completion of runoff.
  • Measure the slope (rise over run, report in per cent)
  • Quantity of sediments may be determined by pouring runoff through preweighed filter paper, then oven-drying the paper.
  • Erosion rate may be determined by calculating the area of the pan (the area of a circle will be close enough), and dividing the oven-dried mass of the eroded soil by the area of the pan, e.g., grams per square centimeter.
  • Use multiple replications. Multiple runs on the same pans is a reasonable estimate, though if the pans are dry at the beginning, the amount of runoff will vary due to differences in infiltration.
  • Vary the treatments, e.g., evaluate the effect of slope (0 to 10%), alter the amount of surface cover, etc.


Updated: 05-03-2013
Copyright, Clay Robinson, PhD, CPSS, PG, 2009.