Mass Wasting Causes of mass wasting Types of mass wasting slumps slumps falls falls slides slides flows flows

Mass Wasting Mass Wasting – downslope movement of debris in response to gravity.

Maximum angle with a stable slope. The coarser the clast size, the more steeply sided a stable pile can be. Angle of Repose

Toe-Cutting and Restabilization Removing the toe of a hill destabilizes it. Material will slide, slump, and creep downhill until the original angle of repose is reestablished. The hill will then be stable.

The Role of Water A little water in the pore spaces of a sediment make the particles “sticky” Too much water between particles force particles apart, and the sediment lose cohesion. Heavy rain and snowmelt are frequently associated with mass wasting.

Landscaping and Landslides Development can lead to mass wasting due to: Removal of slope toes Adding extra weight to a slope Removing vegetation, which encourages erosion Other problems are also common. The slope may look fine, at least until the first heavy rain.

Flow SlideSlump Fall Types of Mass Wasting

Rotational slide, movement occurs along a curved surface so that foot of slump slides outward while the top slides down Slumps Types of Mass Wasting

Slumps have a “scooped out” appearance, with a scarp at the top and debris piled in front of the slump. Slump

“Child Discovers Ice”

icy patch Slump Types of Mass Wasting

Slump Types of Mass Wasting The car and guard rail were at the top of the slump, and dropped almost straight down.

La Conchita, California Landslide and debris flow (1995) Many people were evacuated because of the slide and the houses nearest the slide were completely destroyed. Fortunately, no one was killed or injured. Photograph by R.L. Schuster, U.S. Geological Survey Slump Types of Mass Wasting

Slump Types of Mass Wasting Toe of slump moved outward, bulldozing this house La Conchita, California 1995

The 2005 disaster started with a mud flow over US 101 La Conchita, California

La Conchita, California “The previous photos were from the morning, before the mudslide occurred in our town. It was the most incredible thing I have ever been a witness to. I heard a huge thundering noise, then I made the mistake of looking out my back window only to see a rushing stream of mud and debris flow into a 2-story house, buckling it at the joints and eventually taking it down.” “The previous photos were from the morning, before the mudslide occurred in our town. It was the most incredible thing I have ever been a witness to. I heard a huge thundering noise, then I made the mistake of looking out my back window only to see a rushing stream of mud and debris flow into a 2-story house, buckling it at the joints and eventually taking it down.” 2005

Photos by Frank Spada “My neighbor's house. It has been shifted an entire lot down the street. They both got out safely.” “There used to be about 8 houses here.” “This house is actually pitched forward and up on a pile of mud. “ “The mud flowed right around Ernie's house. Lucky guy...” La Conchita, California 2005

Rock and Debris Falls Types of Mass Wasting Dislodged rocks and debris fall and bounce down cliff.

Rock and Debris Falls Types of Mass Wasting

Rock and Debris Fall Types of Mass Wasting

Yosemite National Park, California Rock fall, 1996 A huge rock weighing 200 tons broke away from Granite Point, near Happy Isles, a popular trailhead and concession stand. The rock disintegrated when it landed, creating an air blast that was so powerful that it flattened as many as 2,000 trees in the area. One person was killed at the concession stand, and 14 people were seriously injured. The dust kicked up from the pulverized granite blocked out the sun and coated tents and recreational vehicles, not unlike ashfall from a volcano. Photograph by Edwin Harp, U.S. Geological Survey. Rock and Debris Falls

Slides Types of Mass Wasting Dislodged rock moves down along a pre-existing surface

Slides Types of Mass Wasting

Fig Slides Types of Mass Wasting A massive rock slide occurred after heavy rain, blocking the Gros Ventre River, and causing all kinds of damage to roads and other structures

Types of Mass Wasting Slides

Cincinnati, Ohio

ODOT Project No. 643 Mt. Adams Slide Repair Location: Hamilton County, Ohio Owner: Ohio Department of Transportation Approximate Value: $22,200,000 Duration of Work: Description: Slide correction consists of installation of ' diameter soldier piles ranging from 20' to 50' deep with rock anchors; 161 caissons (4', 5', 6', 7' diameters) ranging from 20' to 80' deep with rock anchors and tendons to a tunnel bored in rock approximately 100' behind the caisson wall; 1,100 lf of 9' diameter tunnel access shafts in rock. Mt. Adams is the “Rodeo Drive” of Cincinnati

Friday, June 18, 1999 Anti-landslide rules suggested BY ALLEN HOWARD The Cincinnati Enquirer ANDERSON TOWNSHIP — A landslide that caused expensive houses to slip off their foundations in Lawyer's Pointe might not have occurred had the county's improved regulations on hillside development been in effect. […] The landslide in Lawyer's Pointe caused houses with average values of $350,000 to slip off their foundations. To correct the slippage, the township received $1 million from the Federal Emergency Management Agency (FEMA). FEMA has requested that the township adopt hillside regulations that would prevent such slippage on future hillside developments.

Huffman Court A low-cost housing project of single story, single-family homes built in the 1960’s. The original steep (but stable) hillside was greatly altered to make a suitable platform for 15 new houses. Note the position of the creek at the base of the slope adjacent to the development.

Huffman Court A flat area was created by slicing off the top of a steep hill and dumping the fill on one side. The homes were constructed on concrete platforms, i.e., without basements. Problems started to surface about 5 years after construction was completed. Man-made Fill Lake Clay

The overburden of man-made fill pressed on the lake clay, causing it to squeeze out into the creek. Huffman Court

Lake Clay squeezes out into creek, where it is removed by erosion. The land beneath the house sinks, occasionally with visible deformation of the land surface. At some point (usually after a heavy rain), the slope simply gives way, and down goes the house.

Huffman Court By 1971, the land beneath the project had begun to slide, damaging some houses and lots. Over the next 25 years, the landslides claimed three houses, and threatened all the rest. As of 1991, several more houses were already showing signs of damage. A visit in August, 2003 confirmed that another house had been destroyed. A visit in August, 2003 confirmed that another house had been destroyed.