Hillslopes - moving mass: creep,slides and flows
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Hillslopes - moving mass: creep,slides and flows Force balance - driving vs resisting forces Soil creep - slope dependent, diffusive processes Mass movements - landslides and rock falls Flows - of debris and mud. FORCE BALANCE. DRIVING VERSUS RESISTING. GRAVITY. SHEAR STRENGTH (FRICTION

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Hillslopes - moving mass: creep,slides and flows Force balance - driving vs resisting forces

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Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

Hillslopes - moving mass: creep,slides and flows

Force balance - driving vs resisting forces

Soil creep - slope dependent, diffusive processes

Mass movements - landslides and rock falls

Flows - of debris and mud


Force balance

FORCE BALANCE

DRIVING VERSUS RESISTING

GRAVITY

SHEAR STRENGTH (FRICTION

AND COHESION or VISCOSITY)


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf


Processes that move mass on slopes first consider infiltration rate

Processes that move mass on slopesfirst consider infiltration rate

  • Rainsplash (bare soil only)

  • Channels (ephemeral, permanent)

  • Creep (grab-bag, many processes)

  • Mass movement (landsliding = translational, rotational and rockfall)

  • Flowage (debris and mud)


Slope types connect to process

Slope types – connect to process


Rain splash

2

Rainsplash - splatering, downslope component

Rain splash


Where flow is thin rainsplash disturbance prevents channelization

2

Where flow is thin, rainsplash disturbance prevents channelization

Incision begins when shear stress exceeds strength


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

2

Critical Distance from drainage divide = channelization


Soil creep evidence

3

Soil Creep - evidence

Rate is a function of slope Q= ks

Marathon Basin, west Texas. J.S. Aber.

Which way is soil moving?


Other biotic effects vary by climate and location

3

Other biotic effects - vary by climate and location


Mammals gophers here

3

Mammals (gophers here)

NET DOWNSLOPE TRANSPORT


Rotational failure clay silt homogeneous material

Rotational failure - clay, silt, homogeneous material


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

Bishop method of slices

Rotational Failures


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

Importance of unique events/thresholdsDiscrete vs. continuous processesStormsDisturbanceLandslidesDebris Flows


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

The Ritterbush Record

50 cm

2000

2600

Calendar Years BP

5900

6800

8200

9400


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

AMS 14C Analysis


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

Storm Frequency

2

4

6

8

10

12

0

Calendar kyr BP

• 4 maxima; currently increasing—observed?


Hillslopes moving mass creep slides and flows force balance driving vs resisting forces

North

Atlantic

Climate

Storm

Freq.

Coolings

Storms

Floods

GISP2 ssNa

GISP2 nssK

0

2

4

6

8

10

12

Calendar kyr BP


Hillslope channel transition colluvial hollows

Hillslope- channel transition, colluvial hollows


Bank erosion

Bank erosion?


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