Basic Erosion

Question 1

What are the two types of soil erosion?

Answer 1

Geologic (natural) and Accelerated (human induced)

Module 2 / Page 4

Question 2

In general, what percentage of erosion is considered geologic and what percentage is considered accelerated?

Answer 2

30% is considered Geologic
70% is considered accelerated

(Module 2 / Page 4)

Question 3

What are the top two activities contributing to accelerated erosion? And how much accelerated erosion is caused by the leading contributor?

Answer 3

The leading contributor is agriculture causing 72% of accelerated erosion.

The second leading activity of accelerated erosion is construction.

(Module 2 / Page 5)

Question 4

Which activity causes more accelerated erosion on a per acre basis, agriculture or construction?

Answer 4

Construction. 10 to 20 times more on a per acre basis

Module 2 / Page 5

Question 5

What are the five stages of soil erosion?

Answer 5

1. Raindrop erosion
2. Sheet erosion
3. Rill Erosion
4. Gully Erosion
5. Channel Erosion

(Module 2 / Pages 6-11)

Question 6

What is responsible for 90% of soil loss of denuded soil?

Answer 6

Raindrop Impact

Module 2 / Page 6

Question 7

What are some factors that increase the amount of erosion caused by raindrops?

Answer 7

• season of the year
  
  • intensity of storm event
  • size of raindrops
  • speed at which they hit the soil
• length of storm event
• slope
• type of soil (how well water infiltrates)
• land cover

(Module 2 / Pages 7-9)

Question 8

What is the difference between fixing a rill and fixing a gully?

Answer 8

Generally hand tools or other surface treatments can fix a rill. Gullies may require heavy equipment.

(Module 2 / Pages 10-11)

Question 9

When does runoff occur?

Answer 9

Runoff occurs when the rate of rainfall exceeds the infiltration capacity of the soil.

(Module 2 / Page 12)

Question 10

What is sheet erosion’s primary effect?

Answer 10

Transporting previously detached soil particles

Module 2 / Page 12

Question 11

As the volume of concentrated flow increases, what else happens?

Answer 11

Both velocity and turbulence increase

Module 2 / Page 12

Question 12

Yes or no. Can some erosion end up causing even more erosion?

Answer 12

Yes. (Module 2 / Page 12-13)

Example: highly turbulent flow cause large particles like gravel to erode and flow downstream, the partials can then cause more erosion. Additionally, the removal of those particles may make the channel more rough and the water more turbulent, once again causing more erosion.

Question 13

What is soil erosion?

Answer 13

The removal of the land surface by erosive forces such as water, wind, ice, and gravity.

(Module 2 / Page 3)

Question 14

The energy of runoff is based on what factors?

Answer 14

Slope gradient
Slope length
Volume of runoff

(Module 2 / Page 13)

Question 15

What is the primary goal of Virginia’s ESC Program?

Answer 15

Minimizing the impact of accelerated erosion

Module 2 / Page 4

Question 16

How can nutrients attached to sediment negatively affect native aquatic vegetation?

Answer 16

Nutrients stimulate algae growth resulting in algae blooms that shade the native vegetation.
Decaying algae also depletes oxygen in the water.

(Module 2 / Page 23)

Question 17

Sediment can shade the bottom of the waterway or carry harmful particles into the waterway, but how does it directly affect fish?

Answer 17

It can plug their gills or smother their spawning beds.

Module 2 / Page 23

Question 18

Can an excess of sediment in our waterways affect the economy? If so, how?

Answer 18

It can kills fish therefor reduce the income of fisherman or hurt fishing/outdoors tourism.

It can also force drinking reservoirs, harbors and marinas to dredge.

(Module 2 / Page 23)

Question 19

What percentage of our imported good come via water ways requiring functioning harbors and shipping lanes?

A.) 6%
B.) 22%
C.) 46%
D.) 89%

Answer 19

C.). 46%

Module 2 / Page 26

Question 20

What 1930s event marked by severe dust storms across America and Canada created urgency for soil conservation?

Answer 20

The Dust Bowl

Module 3 / Page 1

Question 21

In Virginia, when do the most erosive rains occur? In what month does Richmond, VA typically see the most rain?

Answer 21

Typically between June and September

Richmond receives the most precipitation in July

(Module 2 / Page 9)

Question 22

What is “Sheet Flow”?

Answer 22

Shallow, unconcentrsted and irregular flow down a slope.

9VAC25-840-10 Definitions

Question 23

What five things is the erosive capacity of water based on?

Answer 23

• Velocity
• Turbulence
• Amount and type of abrasive material conveyed by the flow
• Surface or channel roughness
• Slope gradient

(Module 2 / Page 13)