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LAND AND WATER CONSERVATION > 4. Soil Erosion by Water > Flashcards

4. Soil Erosion by Water Flashcards

1
Q

a process by which soil is removed from the
Earth’s surface by exogenetic processes
such as wind or water flow, and then
transported and deposited in other
locations.

A

soil erosion

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2
Q

____ hold soil solid with their roots.
Without them, erosion can lead to
landslides & floods

A

trees

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3
Q

natural erosion (soil-forming and soil
eroding processes) which maintain the
soil in favorable balance.

A

geological erosion

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4
Q

abnormal erosion as a result of
human activities.

A

accelerated erosion

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5
Q

removal of surface soil takes place
at much faster rate than it can be
built up by the soil forming
processes

A

ACCELERATED EROSION

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6
Q

forces involved in accelerated erosion

A

attacking forces
resisting forces

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7
Q

remove and transport the soil particles

A

attacking forces

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8
Q

retard erosion

A

resisting forces

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9
Q

TWO INTERACTIVE PROCESSES

A
  1. DETACHMENT of soil particles from the soil surface.
  2. TRANSPORT of detached particles.
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10
Q

without the _______,
erosion will not even start

A

detachment process

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11
Q

without the ______,
erosion will be much limited

A

transport process

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12
Q

EROSION SUB-PROCESSES

A

Detachment by rainfall
Transport by rainfall
Detachment (scour) by runoff (overland or channelized flow)
Transport by runoff

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13
Q

rainfall amount, intensity and energy
all impact erosion rates

A

climate

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14
Q

erosion due to raindrop splash and
shallow overland flow varies with the
_____

A

rainfall intensity

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15
Q

____ physical properties affect
infiltration capacity

A

soil

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16
Q

______ increases as the
size of the soil particles increases

A

soil detachability

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17
Q

_____ increases with a
decrease in the particle or aggregate
size.

A

soil transportability

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18
Q

interception of rainfall, reducing
surface sealing and runoff

A

vegetation

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19
Q

retardation of erosion by resisting
erosive forces

A

vegetation

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20
Q

decreases soil water,
increased storage capacity, less
runoff.

A

transpiration

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21
Q

slope length and steepness, shape
and size and shape of the watershed

A

topography

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22
Q

on _____, soil is more easily
detached and transported
downslope

A

steep slopes

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23
Q

on _____, an increased
accumulation of overland flow tends
to increase concentrated flow
erosion

A

longer slopes

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24
Q

_____ with flatter slopes
at the foot of the hill, deliver less
sediment than convex slopes.

A

concave slopes.

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25
Q
  • can be naturals such as prolonged
    periods of wet weather
  • human induced such as construction
    or tillage
A

disturbances

26
Q

the greatest natural disturbances in the ecosystems

A

fire

27
Q

may disturb the soil

A

agricultural practices

28
Q

also called as splash erosion

A

raindrop erosion

29
Q
  • soil detachment and transport resulting from the action of raindrop
  • the first stage of soil erosion by water
A

raindrop erosion

30
Q

raindrops increase____,
providing a greater sediment-carrying
capacity

A

turbulence

31
Q

the splashed particles can rise as
high as ___ above the ground and
move up to ____ from the point of
impact

A

0.60 m; 1.5 m

32
Q
  • the removal of soil in thin layers by raindrop impact and shallow surface flow
  • its soil detaching and transporting capabilities are small
A

sheet erosion

33
Q

results in loss of the finest soil particles that contain nutrients
and organic matter in the soil

A

skimming

34
Q

are most vulnerable to sheet erosion

A

overgrazed and cultivated soils with less vegetation

35
Q

the intermittent process of transforming to gully erosion

A

rill erosion

36
Q

are shallow drainage lines <
30 cm deep and 50 cm wide

A

rill erosion

37
Q
  • common in bare agricultural land, overgrazed land and freshly tilled soil where soil structure has been loosened
  • the rills can be obliterated by tillage
A

rill erosion

38
Q

the advanced stage of rills

A

gully erosion

39
Q

is formed when the depth and
width of the rill is > 50 cm

A

gully

40
Q
  • are deeper channels and cannot be removed by normal cultivation
  • flows have high erosive power
  • produce sediment that may clog downstream
A

gullies

41
Q

4 classes of gullies depending upon the depth and width

A

G1, G2, G3 and G4

42
Q

STAGES OF GULLY DEVELOPMENT

A
  1. FORMATION STAGE
  2. DEVELOPMENT STAGE
  3. HEALING STAGE
  4. STABILIZATION STAGE
43
Q

PROCESSES OF GULLY FORMATION

A
  1. Waterfall erosion
  2. Channel erosion
  3. Alternate freezing and melting of snow
  4. Undercutting, landslides, mass movements of soil
44
Q

most of the soil erosion equations were developed in US
basically, splash and sheet erosion estimation

A

SOIL LOSS ESTIMATION

45
Q

E = CS^m1L^M2

A

E = soil loss per unit area from a land slope of unit width;
C = constant reflecting the combined effect of rainfall, soil cover and cover management practices.
S = slope;
L = horizontal length of slope, and m1 and m2 = exponents with estimated values of 1.4 and 0.6, respectively

46
Q

advocated the development of erosion research on
splash erosion. He suggested that splash erosion is a function of soil and rainfall properties

A

Ellison (1945 and 1947)

47
Q

commonly known as the slope-practice
equation but sometimes referred to as

A

Musgrave equation

48
Q

developed an expression for the claypan soils of
Missouri, expressed sheet erosion as

A

Smith and Whitt (1947 and 1948)

49
Q

has gained wide acceptance in the United States and has been adapted by soil conservationists in other countries
its popularity is due to its simplicity and the absence of alternative equations allowing a wider range of variations of the parameters that are contributing to soil erosion

A

THE UNIVERSAL SOIL LOSS ESTIMATION
(USLE)

50
Q

USLE

A

THE UNIVERSAL SOIL LOSS ESTIMATION

51
Q

it estimates sheet erosion as the product of a series of terms for rainfall, soil, slope gradient, slope length, crop and cover management and conservation factors

A

USLE

52
Q

in areas where the USLE applies, it serves as a useful tool for soil conservationists it can be used to:

A

a. predict soil erosion losses
b. guide the selection of agricultural practices such as cropping and management systems
c. guide in determining the on-site effects of land use and crop management changes
d. provide baseline data for conservation planning

53
Q

in the absence of any applicable method for estimating soil erosion rates in tropical
Asia, _____ modified the Universal Soil Loss
Equation to suit locally available information and prevailing environmental conditions

A

David (1986), David and Collado (1987)

54
Q
  • a quantitative measure of erosion potential of rain
  • allows for spatial estimation of basic erosion risks in different areas
A

RAINFALL EROSIVITY, R

55
Q

is reached after 5m fall

A

erosive energy of raindrop

56
Q

KE of falling raindrop is ____

A

0.5mv2

57
Q

the higher the rainfall, the ____ the erosion hazard

A

higher

58
Q

30-60 mm/hr intensities

A

10% of rain is erosive

59
Q

> 100 mm/hr

A

all the rain is erosive

60
Q

5% is erosive in temperate

A

40% in tropical

61
Q

is determined by computing KE for each equal intensity period of storm, multiplied by the RF amount for that period; then these are summed and multiplies by the max. 30-min intensity of the storm

A

erosivity factor (R)

LAND AND WATER CONSERVATION (4 decks)

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