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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. 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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  1. 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

  2. FORCE BALANCE DRIVING VERSUS RESISTING GRAVITY SHEAR STRENGTH (FRICTION AND COHESION or VISCOSITY)

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

  4. 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)

  5. Slope types – connect to process

  6. 2 Rainsplash - splatering, downslope component Rain splash

  7. 2 Where flow is thin, rainsplash disturbance prevents channelization Incision begins when shear stress exceeds strength

  8. 2 Critical Distance from drainage divide = channelization

  9. 3 Soil Creep - evidence Rate is a function of slope Q= ks Marathon Basin, west Texas. J.S. Aber. Which way is soil moving?

  10. 3 Other biotic effects - vary by climate and location

  11. 3 Mammals (gophers here) NET DOWNSLOPE TRANSPORT

  12. Rotational failure - clay, silt, homogeneous material

  13. Bishop method of slices Rotational Failures

  14. Importance of unique events/thresholdsDiscrete vs. continuous processesStormsDisturbanceLandslidesDebris Flows

  15. The Ritterbush Record 50 cm 2000 2600 Calendar Years BP 5900 6800 8200 9400

  16. AMS 14C Analysis

  17. Storm Frequency 2 4 6 8 10 12 0 Calendar kyr BP • 4 maxima; currently increasing—observed?

  18. North Atlantic Climate Storm Freq. Coolings Storms Floods GISP2 ssNa GISP2 nssK 0 2 4 6 8 10 12 Calendar kyr BP

  19. Hillslope- channel transition, colluvial hollows

  20. Bank erosion?

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