RUNOFF EROSION & LANDSLIDES PT.2

Question 1

in what environment is HOF the Dominant flow path

Answer 1

arid, thin vegetation, disturbed land, Gentle slopes,
wide valley bottom, Low/high permeable soil

Question 2

in what environment is SOF the Dominant flow path

Answer 2

Humid, dense vegetation, Undisturbed land, Gentle slopes, wide valley bottom, Low/high permeable soil

Question 3

in what environment is SSF the Dominant flow path

Answer 3

Humid, dense vegetation, Undisturbed land, Steep slopes, narrow valley bottom , deep & permeable soil

Question 4

in what environment is Rilling, sheetwash and rainsplash the dominant erosion process

Answer 4

Arid, thin vegetation, Disturbed land, Gentle slopes,
wide valley bottom, Low/high permeable soil

Question 5

in what environment is Soil creep and
biogenic transport the dominant erosion process

Answer 5

humid, dense vegetation, undisturbed land, Gentle slopes, wide valley bottom, Low/high permeable soil

Question 6

in what environment is ravel the dominant erosion process

Answer 6

Arid, thin vegetation, Disturbed land, Steep slopes,
narrow valley bottom, deep & permeable soil

Question 7

in what environment is Landslides the dominant erosion process

Answer 7

humid, dense vegetation, undisturbed land, Steep slopes, narrow valley bottom, deep & permeable soil

Question 8

what is Rill erosion caused by

Answer 8

water concentrating into innumerable, closely-spaced small channels. Left unchecked, rills -> gullies

Question 9

what is Rainsplash erosion caused by

Answer 9

impact of water striking the surface

Question 10

what kind of chemical erosion occurs In humid regions and what does this mean for the type of load

Answer 10

high chemical weathering -> greater dissolved loads

Question 11

what kind of chemical erosion occurs In arid regions and what does this mean for the type of load

Answer 11

low dissolved loads, high suspended loads (HOF dominates –> more erosion)

Question 12

3 things that cause landslides

Answer 12

• gravity
• water - Small amounts of water = bind grains together / Too much water = adds weight + loosens the soil
• earthquake

Question 13

what happens When Fr > gt,

Answer 13

no movement

Question 14

what happens When Fr < gt,

Answer 14

movement occurs e.g. landslides

Question 15

2 types of land slides

Answer 15

• Slump / earth flow = slow moving piece of land along a spoon-shaped “failure surface.”
• Debris flow = rapid flow of a mixture of rock fragments, soil, mud, and water

Question 16

what kind of topography do landslides (debris flow) tend to occur in

Answer 16

noses (ridges) cause material to move into hollows (valleys) - storms will cause water levels to rise in hollow, destabilising the soil and causing landslide

Question 17

strategies that can be used to reduce the impact of landslides

Answer 17

• avoid placing buildings at the base of steep hillsides.
• particularly avoid placing buildings across the axes of hollows down which a debris flow might travel
• build a strong high wall upslope of the building
• remove the thick soil from the hollows
• attempt to drain the thick soil using pipes
• develop a warning system
• adding vegetation and reducing slope