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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

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)


http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swfhttp://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 slopeshttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swffirst 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 processhttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf


Rain splash

2http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Rainsplash - splatering, downslope component

Rain splash


Where flow is thin rainsplash disturbance prevents channelization

2http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Where flow is thin, rainsplash disturbance prevents channelization

Incision begins when shear stress exceeds strength


2http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Critical Distance from drainage divide = channelization


Soil creep evidence

3http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

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

3http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Other biotic effects - vary by climate and location


Mammals gophers here

3http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Mammals (gophers here)

NET DOWNSLOPE TRANSPORT


Rotational failure clay silt homogeneous material

Rotational failure - clay, silt, homogeneous materialhttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf


Bishop method of sliceshttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

Rotational Failures


Importance of unique events/thresholdshttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swfDiscrete vs. continuous processesStormsDisturbanceLandslidesDebris Flows


The Ritterbush Recordhttp://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf

50 cm

2000

2600

Calendar Years BP

5900

6800

8200

9400


AMS http://ees.as.uky.edu/sites/default/files/elearning/module11swf.swf14C Analysis


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

2

4

6

8

10

12

0

Calendar kyr BP

• 4 maxima; currently increasing—observed?


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

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


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


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