Earth and Environmental Science 11–12 · Year 11
Soil erosion prevention: bare, mulched and planted trays under a measured rainfall (syllabus practical)
Module 4: Human Impacts
The idea
Cover protects soil from raindrop impact and slows runoff, so the same rain on a covered tray moves far less sediment than on bare ground.
What you need
- three or four identical trays (about 40 × 30 × 8 cm) with a drain hole at one end, filled with the same soil to the same depth and compaction
- treatments: bare soil; straw mulch; sown grass grown for 3 weeks; contour furrows across the slope
- watering can with a rose or a sprinkler at fixed height, 1 L per trial, timber offcuts to set a 10 degree slope
- collection beakers, coffee filters, drying oven, balance to 0.01 g
How to do it
- Set all trays at the same slope and apply 1 L of water from the same height over the same 60 s to each in turn.
- Collect all runoff, measure its volume, then filter it and dry the sediment at 105 °C and weigh it.
- Repeat three times per tray; report mean runoff volume and sediment mass per litre of rain.
- Calculate the reduction in sediment for each treatment relative to bare soil.
- Rank the treatments and relate them to farm practice (stubble retention, contour banks, pasture cover).
What you should see
Bare soil produces the most runoff and by far the most sediment; mulch and grass cut both, with established grass cutting sediment by the largest factor. The ratio of each treatment to bare soil is the reported result. The tray rain, 1 L over 60 s on 0.12 m², is 8.3 mm in one minute, an exaggerated intensity of 500 mm/h that makes differences show within a lesson, so the ranking of treatments carries over to farm practice but the sediment masses do not scale to field erosion rates. A sediment concentration in g/L computed from the dried mass and runoff volume makes the comparison independent of how much water ran off.
What changes
- What you change
- surface treatment
- What you measure
- runoff volume (mL) and dry sediment mass (g)
- What you keep the same
- slope
- rain volume, height and duration
- soil type and depth
- starting moisture
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Erosion is caused only by flowing water (raindrop impact detaches soil before runoff carries it away).
- Steeper slopes erode only because water runs faster (splash and rill formation both matter).
Safety card
Hazards
- water on floors
- drying oven
Controls
- work outdoors or in trays
- oven mitts
Note
Heat or hot water is used: follow the NSW Department of Education Chemical Safety in Schools (CSIS) package, Section 1, and record a RiskAssess risk assessment before the lesson.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Earth and Environmental Science Stage 6 Syllabus (2017), NESA; current, replaced by the 11–12 Syllabus (2025) from 2028EES11-11EES11/12-1EES11/12-2EES11/12-3
- Earth and Environmental Science 11–12 Syllabus (2025), NESA; to be implemented from 2028, not yet taughtEES-11-03
- Australian Curriculum v9No Australian Curriculum v9 code is listed.
Sources
The pages the author read to write this activity.
- education.nsw.gov.au/teaching-and-learning/curriculum/science/science-curriculum-resources-k-12/science-11-12-curriculum-resources/earth-and-environmental-science-year-11-and-12
- www.nsw.gov.au/education-and-training/nesa/curriculum/science/earth-and-environmental-science-stage-6-2017
- www.earthlearningidea.com/PDF/61_Dust_bowl.pdf
- www.soilquality.org.au/factsheets/soil-structure