COOLRGuide_Primer_081219

Landslide Reporter
LANDSLIDES @ NASA

The Landslide
Reporter’s Guide

Primer and
Landslide
Identification

landslides.nasa.gov

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Contents
This part of the guide is designed to
give a brief introduction to landslides
and how to identify them.
You will know a little more about:
• Why we study landslides
• Types of landslides
• Our landslide size table (for
Landslide Reporter)

landslides.nasa.gov

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Landslides along a Sikkim road caused by
the 2011 Himalayan earthquake in India.
(Source: AGU/ Sacramento Bee)

Definition of a Landslide
The United States Geological Survey
defines a landslide as “a wide
variety of processes that result in
the downward and outward
movement of slope-forming
materials including rock, soil,
artificial fill, or a combination of
these. The materials may move by
falling, toppling, sliding, spreading,
or flowing”. Landslides can also be
called “landslips” or “mass
movements”.
landslides.nasa.gov

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Where can landslides
happen?
Landslides occur in all environments
and nearly every country.
They can be caused by natural
processes like rain or earthquakes
or by manmade processes like
mining or pipe leaks.

This NASA landslide susceptibility map
shows the global impact of landslides due
to rainfall. (Source: NASA)
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landslides.nasa.gov

Why study landslides?
Worldwide, landslides cause billions
of dollars in infrastructural damage
and thousands of deaths every year.
Often, it’s not exactly known when
and where a landslide will occur,
resulting in unexpected loss of life
and destruction of roads, buildings,
and property.
More data about past landslide
events guides awareness and action
to protect against landslide hazards
and enables researchers to study
their future impact.
Aerial photo of the 2014 Oso mudslide that
killed 43 people in Oso, Washington, USA.
(Source: AP)

landslides.nasa.gov

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Landslide Categories
In order to classify a landslide, we
need to look at both the material
and the movement.
• First, think about material.

Soil

Onwards to movement analysis

Material

Rock

Mostly fine grains?
Very small particles like
silt, clay, or mud
Mostly coarse grains?
Larger particles
anywhere from sand to
boulder-size particles

Snow

Volcanic

Snow avalanche
Lahar (a type of mudslide
that flows down the slope
of a volcano)
landslides.nasa.gov

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Landslide Categories
• Next, think about movement.
Slides

Falls

The mass breaks off from
the underlying layer and
slides downslope atop the
underlying layer.
Masses of soil or rock
dislodge from a steep slope
and fall vertically downwards.

Topples The mass breaks off and

pivots forward around an axis
below the displaced mass.

Flows

Creep

The mass is saturated with
water and viscous enough to
flow rapidly downslope.
The mass moves
imperceptibly slow
downwards as a result of
shear stress, but does not
break off completely.

Content adapted from USGS and the California Geological Survey

landslides.nasa.gov

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Landslide Categories
Once you have defined the landslide
material and movement, use the
tables and guides on the next pages
to determine whether the landslide
is one of the below categories.
•
•
•
•
•
•
•

Landslide
Mudslide
Debris flow
Rock fall
Translational slide
Rotational slide
Complex

•
•
•
•
•
•

Topple
Riverbank collapse
Lahar
Earth flow
Snow avalanche
Creep

landslides.nasa.gov

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Adapted from an abbreviated version of
Varnes’ (1978) landslide classification. White
boxes are options in Landslide Reporter.
(Source: USGS)

Type of material
Type of movement

Bedrock

Engineering soils

Mostly fine Mostly coarse
Falls

Rock fall

Earth fall

Debris fall

Topples

Rock topple

Earth
topple

Debris topple

Rock slide

Debris slide Earth slide
(Landslide) (Landslide)

Rock spread

Earth
spread

Debris
spread

Rock flow

Earth flow
(Mudslide)

Debris flow

Rotational
Slides
Translational

Lateral spreads

Flows

Rock
avalanche
Deep creep

Complex and
compound

Debris
avalanche
Soil creep

Combination in time and/or space of two
or more principal types of movement

landslides.nasa.gov

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Ilustrated Examples 1: Landslide diagrams as
classified by the United States Geological
Survey (Source: USGS)

landslides.nasa.gov

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Illustrated Examples 2: Landslides as
classified by the British Geological Survey
(Source: BGS)

landslides.nasa.gov

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Estimated Size
The relative size of the landslide.
Use the table below to approximate
the size of a landslide event.

Medium

Small

Descriptors

Volumes

Small landslide affecting one hillslope <10 cubic
or small area. Minimal impacts to
meters
infrastructure and roads. One road is
blocked, cleaned in a few hours; one
dump truck needed to clear the dirt;
usually no fatalities
Moderately sized landslide that could
be either a single event or multiple
landslides within an area, and
involves a large amount of material.
Road is blocked for multiple days;
multiple roads blocked; multiple
houses damaged; multiple dump
trucks needed to clear the dirt;
sometimes at least one fatality

10 to
<1000
cubic
meters

(table is continued on next page)
landslides.nasa.gov

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Estimated Size

Catastrophic Very Large

Large

The relative size of the landslide.
Use the table below to approximate
the size of a landslide event.
Descriptors
Large landslide or series of landslides
that occur in one general area but
cover a wide area. Substantial
impacts to infrastructure and roads,
likely moderate to high number of
fatalities. Tens to hundreds of people
displaced.

Volumes
1000 to
<100,000
cubic
meters

Very large landslide or multiple events
that affect an entire region (often
encompassing an entire village).
Thousands of people may be
displaced, may be high numbers of
fatalities.

100,000 to
<1 million
cubic
meters

Catastrophic impacts to infrastructure ≥1 million
and roads. Multiple villages,
cubic
neighborhoods, towns buried. Tens of meters
thousands of people may be
displaced. May be hundreds to
thousands of fatalities.
landslides.nasa.gov

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Finish
Congratulations,
you learned the basics of
landslide reporting for
COOLR!
Thank you for reading through this
landslide primer. Use this guide to
help you identify landslides for your
reports, and keep it handy when you
complete the Landslide
Identification Training chapter of this
guide.

landslides.nasa.gov

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Landslide Reporter
LANDSLIDES @ NASA
landslides.nasa.gov

landslides.nasa.gov

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