Mass Wasting & Soil Survey

Objectives

• Show some case studies of how soil surveys handle landslides.– Guam– North Dakota– Alabama– California

• Discussion: are we doing enough?– Are we alerting our users to conditions and

potentials for slope failures?

Island of Guam

Affected by rotational landslides, in certain soils.

Just looking at the DEM, can you guess where they occur?

Eocene, Oligocene & Miocene;tuff, tuff breccia, tuffaceous sandstone/shale

Pliocene & Pleistocene;Reef complex, reef detritus

SSURGO soils of GuamGrouped by parent material (mostly)

Typical slides in soft, deeply weathered volcanic saproliteAnthropic grasslands are incapable of stabilizing this material:

tectonic uplift; deeply dissected; 80-100” rainfall; seasonally distributed

All pictures by Bob Gavenda, SS in Guam

Slides are extensive

Zoomed-in view of slide areas

Note recent burns; an aggravating factor

So… how would you map this?

Akina series: Inceptic Haplustoxv. fine, kaolinitic, isohyperthermic

Akina – Badland complexes(various slope classes)

SSURGO delineations of Akina-badlands cpx.

Rotational Slides provide parent material for Togcha soils in footslope positions

Akina (residuum in saprolite)

Togcha (“slope alluvium” in SS; what should we call it?)

Note: taxonomic classifications shown are out of date.

The soil survey does not clearly address the issue of rotational slides.

Slides and soil survey in North Dakota

McKenzie county

Barnes county

McKenzie county, NDLots of badlands – any slides?

Little Missouri R

IFSAR hillshade added…Do the slides stand out more?

Here’s how they mapped it…

Another view:IFSAR w hillshade

116F—Kremlin-Cabbart loams, slumped, 9 to 40 percent slopes

Setting:Kremlin soils occur on footslopes.Cabbart soils occur on summits and shoulders.This map unit occurs on ridges that are slumped in badlands.

Map Unit Composition (percent)Named Components

Kremlin and similar soils: 15 to 45 percentCabbart and similar soils: 15 to 50 percent

Average Component CompositionCabbart: 29 percentKremlin: 19 percentBoxwell: 17 percentScairt: 14 percentLonna: 13 percentBadland, outcrop: 5 percentFleak: 3 percent

From the soil survey manuscript (Aziz et al, 2006)

Valley City, NDBarnes county. Sheyenne R., I-94 at Valley City.

Where are the slides?

From Anderson (2004), NDGS

LiDAR & SSURGO

Kloten – Buse cpx., 9-35%Kloten: shale @ <20”Buse: till

From Soil Survey: Kloten – lower side slopes Buse – upper side slopes, shoulders, & summits

Note “bumpy” texture of LiDAR in the Kloten-Buse 9-35% unit

From hard-copy soil survey:Not readily available to public

How can we incorporate our knowledge of potential slippage more explicitly into the soil survey?

Mass movement and soil survey in Huntsville, AL (Madison county).

Viewed on a 2009 SGI field trip.

Spectacular rotational slide near Huntsville, AL

Plateau summit

Steep slopes

Fancy houses

Oblique view from ArcGIS Explorer

Slope failure (main scarp) at contact of overlying sandstone with underlying shale.Soil survey lines follow this contact.Can we capture this information in SSURGO?

Soil Survey of Napa county, CA

Fagan clay loam, 30-50% slopes, slumped

Fine, smectitic, Typic Argiudolls

40-60” to Cr sandstone

Associated with marine sediments(?)

Summary and Discussion

• Mass wasting is handled in various ways in county soil surveys:– Components; e.g., badlands– Map unit name; e.g. slumped

• Failure zones are implicitly identified in county soil surveys:– Contrasting components within map units– Boundaries between map units

• Discussion: can we do better?– i.e., clearly alert users to landslide activity and hazards, both

spatially (maps) and in attributes / interpretations.