Basic Soil Flashcards
Which of the following describes clay particle properties?
A) hard to erode but easily carried as runoff
B) easy to erode and easily carried as runoff
C) hard to erode and hard to be carried as runoff
D) easy to erode and hard to be carried as runoff
A.). High clay soils are more resistant to detachment, but once detached are easily transported and suspended in solution
(Module 2 / Page 16)
What role does organic material play in the structure of soil? Organic material makes soils…
organic material makes soil…
MORE permeable and MORE stabile
(Module 2 / Page 16)
Soils with what types of particles have the HIGHEST erodibility?
Silt particles and fine sands
Module 2 / Page 16
Clay soils are resistant to detachment but what negative might they have on a construction site?
Clay soils have poor infiltration which will increase runoff
Module 2 / Page 17
What is a “k-factor” used to describe?
K-factors can be used to describe how susceptible the soil is to erosion.
(Module 2 / Page 18)
Slope steepness influences erodibility. What slope gradient constitutes a steep slope and a HIGH erosion hazard?
15% and over is considered a high erosion hazard.
Module 2 / Page 18
What is the difference between convex slopes and concave slopes?
Convex slope means steeper at the lower end.
Concave slopes flatten at the lower end.
(Module 2 / Page 19)
Between convex and concave slopes, which has the higher potential for erosion?
Convex slopes have a higher potential for erosion
Module 2 / Page 19
A slope has a length of 100’ and a 4% slope. Do these criteria constitute a critical erosion hazard?
No.
With a slope between 0-7%, it would require a length of 300 ft or more to constitute a critical erosion hazard.
(Module 2 / Page 19)
What is the most important factor to minimize erosion?
Maintaining surface cover
Module 2 / Page 20
How effective is permanent grass at reducing soil erosion? (Provide a percentage)
permanent grass reduces soil erosion by 99%
Module 2 / Page 20
How effective is mulch/wood chips/ wood cellulose fiber at reducing soil erosion? (Provide a percentage)
Wood chips and similar mulching materials are usually 90% effective.
(Module 2 / Page 20)
What may be some soil properties used to develop a K factor?
- Permeability
- Particle Size Distribution
- Organic Matter content
- Soil structure
(Module 2 / Page 16)
What is the range of slope gradients that are considered low erosion hazards? What is the range that is considered moderate erosion hazards?
0-7 % is considered LOW
7-15% is moderate and above 15% is high
(Module 2 / Page 18)
Would a slope of 13% gradient and 400 feet in length be considered a critical erosion hazard?
Yes. Between 7 and 15% any slope longer than 150’ would be considered a critical erosion hazard.
(Module 2 / Page 19)
What effect can freezing temperatures have on soil?
Freezing temperatures can destroy the soil structures and destabilize the soil when water in the soil expands.
(Module 2 / Page 15)
What effect(s) can wind have on a soil?
Wind can dry out a soil and reduce cohesiveness.
Module 2 / Page 15
What effect(s) can warm weather have on soil?
Warm temperatures can bake the soil and this can destroy the soil structure.
(Module 2 / Page 15)
What is permeability?
The rate at which water will move through the soil.
Module 2 / Page 17
In relation to soil, what does “bulk density” mean?
How tightly soil particles are packed together.
Module 2 / Page 15
What equation describes long-term average soil losses expected from sheet and rill erosion for agricultural land use and is able to illustrate how implementation of ESC measures may reduce erosion potential?
The Universal Soil Loss Equation or USLE
Module 2 / Page 30
Describe what K-factor values represent low erodibility, moderate erodibility, and high erodibility.
- 23 and lower is considered low erodibility
- 24 to 0.36 is considered moderate erodibility
- 36 and higher is considered high erodibility
(Module 2 / Page 18)
