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

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

AND COHESION or VISCOSITY)


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


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


2

Rainsplash - splatering, downslope component

Rain splash


2

Where flow is thin, rainsplash disturbance prevents channelization

Incision begins when shear stress exceeds strength


2

Critical Distance from drainage divide = channelization


3

Soil Creep - evidence

Rate is a function of slope Q= ks

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

Which way is soil moving?


3

Other biotic effects - vary by climate and location


3

Mammals (gophers here)

NET DOWNSLOPE TRANSPORT


Rotational failure - clay, silt, homogeneous material


Bishop method of slices

Rotational Failures


Importance of unique events/thresholdsDiscrete vs. continuous processesStormsDisturbanceLandslidesDebris Flows


The Ritterbush Record

50 cm

2000

2600

Calendar Years BP

5900

6800

8200

9400


AMS 14C Analysis


Storm Frequency

2

4

6

8

10

12

0

Calendar kyr BP

• 4 maxima; currently increasing—observed?


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


Bank erosion?


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