Soil Science and Erosion Fundamentals Flashcards

What is the difference between 'erosion' and 'sedimentation' in the context of ESC?

Answer: Erosion is the detachment and transport of soil particles; sedimentation is the deposition of those transported particles in a new location

Erosion occurs at the source where soil is detached and moved; sedimentation is what happens downstream when transported particles lose momentum and settle, often clogging channels or water bodies.

Which condition makes soils most susceptible to erosion during construction?

Answer: Bare, freshly disturbed soils with no vegetative cover on slopes during high-intensity rainfall

Disturbed soils lack protective vegetation and aggregate structure, making them extremely vulnerable to raindrop impact and runoff — conditions that are precisely what construction creates.

What is 'sheet flow' and why is it important to understand for ESC?

Answer: Thin, relatively uniform overland flow across the soil surface before it concentrates into rills or channels

Sheet flow is the initial stage of runoff before it concentrates; understanding it informs the placement of silt fences and other interceptor BMPs that work on thin, dispersed flows.

Why is it important to preserve and reuse topsoil stockpiled during construction?

Answer: Topsoil contains the organic matter, nutrients, and soil structure necessary for vegetation establishment, making revegetation faster and more successful

Topsoil's biological and physical properties support plant establishment far better than subsoil; spreading it back over disturbed areas after grading accelerates permanent stabilization.

What is the primary mechanism by which mulch reduces soil erosion?

Answer: By absorbing raindrop impact energy and slowing runoff velocity, protecting the soil surface from detachment

Mulch intercepts falling raindrops before they impact bare soil, and it slows runoff by creating surface resistance, both dramatically reducing detachment and transport of soil particles.

How does freeze-thaw cycling affect soil erodibility on construction sites?

Answer: Repeated freezing and thawing disrupts soil structure and increases erodibility by breaking up aggregates and leaving soil loose and vulnerable

As water in soil pores freezes and expands, it breaks apart soil aggregates; when the ice melts, the disturbed, loosened particles are highly vulnerable to erosion by rainfall and runoff.