Soil Science and Erosion Fundamentals Flashcards

What role does organic matter play in soil erodibility?

Answer: Organic matter decreases erodibility by improving soil aggregate stability, water-holding capacity, and infiltration

Organic matter binds soil particles into stable aggregates that resist raindrop impact and runoff, and it improves infiltration, both of which reduce erosion.

Which soil horizon is typically most vulnerable to erosion when exposed by construction grading?

Answer: The B or C horizon subsoils exposed after topsoil stripping

Subsoil horizons (B and C) typically have poor structure, low organic matter, and high clay content, making them more erodible and difficult to revegetate than topsoil.

What is 'soil erodibility' as measured by the K factor in the USLE?

Answer: The susceptibility of soil to detachment and transport by rainfall and runoff

The K factor quantifies how easily a specific soil type is detached by rainfall and transported by runoff, integrating texture, structure, organic matter, and permeability.

What is the effect of vegetative cover on soil erosion rates?

Answer: Vegetation dramatically reduces erosion by intercepting rainfall, binding soil with roots, and slowing runoff

A well-established vegetative cover can reduce erosion by more than 99% compared to bare soil by intercepting raindrop energy, increasing infiltration, and binding soil particles with roots.

What is 'gully erosion' and why is it significant on construction sites?

Answer: Advanced-stage erosion where rills merge into large, deep channels that cannot be crossed by equipment, indicating severe loss of soil

Gully erosion represents extreme concentration of runoff that has cut deeply into the soil, removing large volumes of material and potentially destabilizing adjacent areas.

How does the slope length factor (L) in the USLE affect predicted soil loss?

Answer: Longer slopes allow more runoff to accumulate and accelerate, increasing erosive power and predicted soil loss

As runoff travels down a longer slope, it accumulates more volume and velocity, increasing its erosive energy and the quantity of sediment it can transport.