CEPSCI Soil Science and Erosion Fundamentals 1 — Questions and Answers
Question 1: What are the three types of soil particles, listed from largest to smallest?
- Gravel, sand, silt
- Sand, silt, clay (Correct answer)
- Clay, silt, sand
- Loam, sand, gravel
Correct answer: Sand, silt, clay
Soil texture is determined by the relative proportions of sand (0.05–2 mm), silt (0.002–0.05 mm), and clay (<0.002 mm) particles.
Question 2: Which soil textural class is generally considered most erodible by water?
- Clay
- Gravel and coarse sand
- Silt and fine sand (Correct answer)
- Organic peat soils
Correct answer: Silt and fine sand
Silt and fine sand particles are large enough to be detached by raindrop impact but small enough to be transported easily in runoff, making them highly erodible.
Question 3: What is 'raindrop splash erosion' (interrill erosion)?
- Erosion caused by concentrated channel flow
- Erosion caused by the impact of raindrops detaching soil particles and splashing them into suspension (Correct answer)
- Erosion of stream banks by flowing water
- Wind erosion on a construction site
Correct answer: Erosion caused by the impact of raindrops detaching soil particles and splashing them into suspension
Raindrop impact breaks up soil aggregates and detaches particles, making them available for transport by surface runoff — this is the first stage of water erosion.
Question 4: The Universal Soil Loss Equation (USLE) estimates:
- The total volume of stormwater runoff from a site
- Average annual soil loss from a field based on rainfall, soil erodibility, slope, cover, and management factors (Correct answer)
- The depth to groundwater beneath a site
- The cost of erosion damage to downstream properties
Correct answer: Average annual soil loss from a field based on rainfall, soil erodibility, slope, cover, and management factors
The USLE combines the R (rainfall erosivity), K (soil erodibility), LS (slope length and steepness), C (cover and management), and P (support practice) factors to estimate erosion rates.
Question 5: What is soil compaction, and why is it a concern on construction sites from a stormwater perspective?
- Soil compaction makes soil stronger, which is always beneficial for erosion control
- Compaction reduces soil porosity and infiltration capacity, increasing stormwater runoff volume (Correct answer)
- Compaction improves soil structure and vegetation establishment
- Compaction has no effect on stormwater runoff
Correct answer: Compaction reduces soil porosity and infiltration capacity, increasing stormwater runoff volume
Heavy equipment compacts soil, reducing pore space and hydraulic conductivity, which means more rainfall becomes runoff rather than infiltrating — increasing erosion and stormwater discharge volumes.
Question 6: What is 'rill erosion' and how does it differ from sheet erosion?
- Rill erosion is wind erosion; sheet erosion is water erosion
- Sheet erosion removes a uniform thin layer of soil; rill erosion involves concentrated flow that carves small channels into the soil surface (Correct answer)
- Rill erosion only occurs near streams; sheet erosion occurs everywhere
- They are the same process described by different terms
Correct answer: Sheet erosion removes a uniform thin layer of soil; rill erosion involves concentrated flow that carves small channels into the soil surface
Sheet erosion is the relatively uniform removal of thin soil layers, while rill erosion begins when runoff concentrates into small channels, greatly increasing erosive power and sediment delivery.
CEPSCI Soil Science and Erosion Fundamentals 1
What are the three types of soil particles, listed from largest to smallest?