There are many different means of investigating the landslide-prone areas. Two types of landslide hazard evaluation methods are available. One is the direct observation and the other one is the use of technological tools. One of the guiding principles of geology is that the past is the key to the future. In evaluating landslide hazards, the future slope failures could occur as a result of the same geologic, geomorphic, and hydrologic situations that led to past and present failures. Based on this assumption, it is possible to estimate the types, frequency of occurrence, extent, and consequences of slope failures that may occur in the future. A landslide susceptibility map goes beyond an inventory map and depicts areas that have the potential for landsliding.

1. Landslide Hazard Zonation
Mapping
BY
Prof. A. Balasubramanian
Centre for Advanced Studies in Earth Science,
University of Mysore,
Mysore-6

2. Landslide
• Is the down slope movement
of loose soil, uncompact
rock, and organic materials,
• under the effects of gravity
along a sliding plane,
• Triggered by severe Rf, Sws,
wt of overburden.
• Creates a new landform
resulting from such
movement.
• Hazardous/ disastrous.

3. Landslides
• associated with specific mechanics of slope
failure and the properties and characteristics
of failure types.
• Landslides are experienced in the hilly and
mountainous areas, all over the world.
• May start from the top of a hill slope and
move till the end of foot hill,
• or may start from the bottom of a hill slope,
drawing all materials from the top to bottom.

4. Mass movement
• It is the movement of surface
material caused by gravity.
Landslides and rockfalls
are examples of very
sudden movements of this type.
• Of course geological agents such
as water, wind and ice all work
with gravity to cause a leveling of
land.

5. Hill slopes
• Hills and mountains are typical geomorphic
features.
• They are characterized by gentle or steep
slopes.
• They are unique climatic zones.
• They are characterized by thick soil profiles,
richness with soil moisture and plant growth.

6. Landslides as natural hazards
• Landslides normally occur on hill slopes.
• When the slopes are stable there will be no
problem.
• When the slopes become unstable then they
may lead to landslides.

7. • Landslides occur when the stability of the
slope changes from a stable to an unstable
condition.
• The change in the stability of a slope may
happen due to several factors.
• These factors may be acting alone or acting
together.

8. • The overburden may be mostly loose soil,
may have a thick weathered zone, adequate
natural or man-made vegetation, good root
penetration, and all are under the direct
influence of Climatic variations, especially
rainfall.

9. Slope and bedrocks
• The Bedrock is related to the basement rocks
of the hill.
• These may be massive or fresh, structurally
weak or deformed.
• All of these may be under the influence of a
tectonic force originating from the deep
interior or a nearby huge structure like a
dam.

10. • The next factor is the degree of slope of the
area.
• Slope is a common factor for a landslide.
• The categories of slope is to be understood
first.
• It varies depending upon the geomorphic
conditions, bedrock, nature of overburden,
vegetation and drainage systems.

11. Slope
• A slope is the rise or fall of the land surface.
• It is important for the farmer or irrigator to
identify the slopes on the land.

12. TYPES OF SLOPES
• Gentle
• Steep
• Concave
• Convex

13. • The slope of line a is m=5/6
• The slope of line b is m= -1/4
• The slope of line c is m= 3/7
• The slope of line d is m= -6/3 or m=-2
• The slope of line e is m= 0 (but how do you use m= rise/run
to get this number?)

14. Categories of slopes
• The following are the categories of slopes:
• Cliff > 80 degrees
• Precipitous 50-80 degrees
• very steep or steep 20-50 degrees
• moderate slope 6-20 degrees
• gentle slope 1-6 degrees
• flat terrain < 1 degree.

15. Slope (%)
Approximate
degrees
Terminology
0 - 0.5 0 Level
0.5 - 2 0.3 - 1.1 Nearly level
2 - 5 1.1 - 3 Very gentle slope
5 - 9 3 - 5 Gentle slope
9 - 15 5 - 8.5 Moderate slope
15 - 30 8.5 - 16.5 Strong slope
30 - 45 16.5 - 24 Very strong slope
45 - 70 24 - 35 Extreme slope
70 - 100 35 - 45 Steep slope
> 100 > 45 Very steep slope

17. Slope may be expressed in several
ways
• but all depend upon the
comparison of vertical
distance (VD) to horizontal
distance (HD).
• Before we can determine the
percentage of a slope, we
must know the VD of the
slope. The VD is determined
by subtracting the lowest
point of the slope from the
highest point.

21. Overburden soils and Bedrocks
• Rock type
• Structure
• Dip and strike
• Soil profile- properties of soils
• Rock material properties
• Rock mass properties
• & lastly Triggering mechanisms.

22. What do these pictures show?

52. Parts of a landslide zone

54. Landslide classification
• The landslide classification based on Varnes'
(1978)system has two terms:
• -the first term describes the material type,-
the second term describes the type of
movement.

55. The material types- Rock, Earth, Soil,
Mud and Debris
• Rock: is “a hard or firm mass that was intact
and in its natural place before the initiation of
movement”.
• Soil: is “an aggregate of solid particles,
generally of minerals and rocks, that either
was transported or was formed by the
weathering of rock in place. Gases or liquids
filling the pores of the soil form part of the
soil”.

56. • Earth: “describes material in which 80% or
more of the particles are smaller than 2mm,
the upper limit of sand sized particles”.
• Mud: “describes material in which 80% or
more of the particles are smaller than
0.06mm, the upper limit of silt sized particles”.
• Debris: “contains a significant proportion of
coarse material; 20% to 80% of the particles
are larger than 2mm, and the remainder are
less than 2mm”.

57. VARNES´ CLASSIFICATION OF SLOPE
MOVEMENTS
• The five kinematically distinct types of movement are
described in the sequence: - fall, - topple, - slide, -
spread, - flow.
• Combining the two terms gives classifications such as:
• Rock fall,
• Rock topple,
• Debris slide,
• Debris flow,
• Earth slide,
• Earth spread, etc.

64. Landslides: Rock Fall
• Rock Falls are the
detachment of rock
from a steep slope along
a surface on which little
or no shear
displacement takes
place. The material then
descends largely by
falling, bouncing or
rolling.

65. Rock Fall -Diagnostic Characteristics
• A fall starts with the detachment
of soil or rock from a steep slope
along a surface on which little or
no shear displacement takes
place. The material then
descends largely by falling,
bouncing or rolling. Free fall
movement of material from a
steep slope or cliff, EPOCH
(1993).

66. • Toppling failures are
distinguished by the
forward rotation of a
unit about a pivot
point.
Typically involving
tall columns of rock
Vertical or steeply
dipping
discontinuities
behind the block
allow the rock mass
to topple out of the
face and second set
of orthogonal joints,
which defines the
column height.

67. Landslides: Rock Topple
• A topple is the
forward rotation, out
of the slope, of a
mass of soil and rock
about a point or axis
below the centre of
gravity of the
displaced mass.

68. Landslides: Rock Topple Diagnostic
Characteristics
• Toppling failures are distinguished by
the forward rotation of a unit about a
pivot point.
• Typically involving tall columns of rock.
Vertical or steeply dipping
discontinuities behind the block allow
the rock mass to topple out of the face
and second set of orthogonal joints,
which defines the column height.
Similar to a fall but involves a pivoting
action rather than a complex
separation at the base of the failure,
EPOCH (1993).

69. Rock Topple Diagnostic
Characteristics

70. Landslides: Rock & Block Slide
• A slide is the
downslope
movement of a soil
or rock mass
occurring
dominantly on the
surface of rupture
or relatively thin
zones of intense
shear strain.

84. Types of landslides

85. Translational slides move along a flat
slippery zone.

86. Rotational slides move along a concave
(bowl shaped) slippery zone.

99. Common types of slope failure

105. What Causes Landslides?
• There are two primary categories of causes of
landslides: natural and human-caused.
Sometimes, landslides are caused, or made
worse, by a combination of the two factors.
• Natural Occurrences
• This category has three major triggering
mechanisms that can occur either singly or in
combination —
• (1) water, (2) seismic activity, and (3) volcanic
activity.

106. • Effects of all of these causes vary widely and
depend on factors such as steepness of slope,
morphology or shape of terrain, soil type,
underlying geology, and whether there are
people or structures on the affected areas.

107. Landslide Causes and Triggering
Mechanisms
• Physical Causes—Triggers
• Intense rainfall
• Rapid snowmelt
• Prolonged intense precipitation
• Rapid drawdown (of floods and tides) or filling
• Earthquake
• Volcanic eruption
• Thawing
• Freeze-and-thaw weathering
• Shrink-and-swell weathering
• Flooding.

108. Natural Causes: Geological causes
• Weak materials, such as some volcanic slopes or unconsolidated
marine sediments, for example
• Susceptible materials
• Weathered materials
• Sheared materials
• Jointed or fissured materials
• Adversely oriented mass disconti nuity (bedding, schistosity, and so
forth)
• Adversely oriented structural discontinuity (fault, unconformity,
contact, and so forth)
• Contrast in permeability
• Contrast in stiffness (stiff, dense material over plastic materials)

109. Natural Causes: Morphological causes
• Tectonic or volcanic uplift
• Glacial rebound
• Glacial meltwater outburst
• Fluvial erosion of slope toe
• Wave erosion of slope toe
• Glacial erosion of slope toe
• Erosion of lateral margins
• Subterranean erosion (solution, piping)
• Deposition loading slope or its crest
• Vegetation removal (by forest fire, drought)

110. Human Causes
• Excavation of slope or its toe
• Use of unstable earth fills, for construction
• Loading of slope or its crest, such as placing earth fill at the top of a
slope
• Drawdown and filling (of reservoirs)
• Deforestation—cutting down trees/logging and (or) clearing land
for crops; unstable logging roads
• Irrigation and (or) lawn watering
• Mining/mine waste containment
• Artificial vibration such as pile driving, explosions, or other strong
ground vibrations
• Water leakage from utilities, such as water or sewer lines
• Diversion (planned or unplanned) of a river current or longshore
current by construction of piers, dikes, weirs, and so forth

111. Landslides and Water
• Slope saturation by water is a primary cause of
landslides.
• Saturation can occur in the form of intense
rainfall, snowmelt, changes in ground-water
levels, and surface-water level changes along
coastlines, earth dams, and in the banks of
lakes, reservoirs, canals, and rivers.

112. Landslides and Seismic Activity
• Many mountainous areas that are vulnerable to
landslides have also experienced at least
moderate rates of earthquake activity in recorded
times.
• Earthquakes in steep landslide-prone areas
greatly increase the likelihood that landslides will
occur, due to ground shaking alone, liquefaction
of susceptible sediments, or shaking-caused
dilation of soil materials, which allows rapid
infiltration of water.

113. • Rockfalls and rock topples can also be caused
by loosening of rocks or rocky formations as a
result of earthquake ground shaking.

114. Landslides and Volcanic Activity
• Landslides due to volcanic activity represent
some of the most devastating types of failures.
• Volcanic lava may melt snow rapidly, which can
form a deluge of rock, soil, ash, and water that
accelerates rapidly on the steep slopes of
volcanoes, devastating anything in its path.
• Volcanic edifices are young, unconsolidated, and
geologically weak structures that in many cases
can collapse and cause rockslides, landslides, and
debris avalanches.

115. Human Activities and landslides
• Populations expanding onto new land and
creating neighborhoods, towns, and cities is
the primary means by which humans
contribute to the occurrence of landslides.
• Disturbing or changing drainage patterns,
destabilizing slopes, and removing vegetation
are common human-induced factors that may
initiate landslides.

116. Human activities and landslides
• landslides may also occur in once-stable areas
due to other human activities such as irrigation,
lawn watering, draining of reservoirs (or creating
them), leaking pipes, and improper excavating or
grading on slopes.
• New construction on landslide-prone land can be
improved through proper engineering (for
example, grading, excavating) by first identifying
the site’s susceptibility to slope failures and by
creating appropriate landslide zoning.

117. Mining

118. Evaluating Landslide Hazards
• There are many different means of assessing
landslide hazard for an area; it is always
advisable to consult with an expert for the
most accurate assessment, although this is not
always possible.
• Two types of landslide hazard evaluation,
direct observation and the use of
technological tools.

119. Features that might indicate landslide
movement:
• Springs, seeps, and wet or saturated ground in previously dry areas
on or below slopes.
• Ground cracks—cracks in snow, ice, soil, or rock on or at the head of
slopes.
• Sidewalks or slabs pulling away from structures if near a slope; soil
pulling away from foundations.
• Offset fence lines, which were once straight or configured
differently
• Unusual bulges or elevation changes in the ground, pavements,
paths, or sidewalks.
• Tilting telephone poles, trees, retaining walls, fences.
• Excessive tilting or cracking of concrete floors and foundations.
• Broken water lines and other underground utilities.

120. Indications of sliding lands
• Rapid increase or decrease in stream-water
levels, possibly accompanied by increased
turbidity (soil content clouding the water).
• Sticking doors and windows and visible open
spaces, indicating walls and frames are shifting
and deforming.
• Creaking, snapping, or popping noises from a
house, building, or grove of trees (for example,
roots snapping or breaking).
• Sunken or down-dropped roads or paths.

121. Technological Tools for Evaluation of
Landslides
• One of the guiding principles of geology is that
the past is the key to the future.
• In evaluating landslide hazards this means
that future slope failures could occur as a
result of the same geologic, geomorphic, and
hydrologic situations that led to past and
present failures.

122. • Based on this assumption, it is possible to
estimate the types, frequency of occurrence,
extent, and consequences of slope failures
that may occur in the future.
• However, the absence of past events in a
specific area does not preclude future failures.
• Human-induced conditions, such as changes in
the natural topography or hydrologic
conditions, can create or increase an area’s
susceptibility to slope failure.

123. Predicting landslide hazards
• In order to predict landslide hazards in an area,
the conditions and processes that promote
instability must be identified and their relative
contributions to slope failure estimated, if
possible.
• Useful conclusions concerning increased
probability of landsliding can be drawn by
combining geological analyses with knowledge of
short- and long-term meteorological conditions.

124. Map Analysis
• Map analysis is usually one of the first steps in
a landslide investigation. Necessary maps
include bedrock and surficial geology,
topography, soils, and if available,
geomorphology maps.
• Using knowledge of geologic materials and
processes, a trained person can obtain a
general idea of landslide susceptibility from
such maps.

125. Aerial Reconnaissance
• Analysis of aerial photography is a quick and
valuable technique for identifying landslides,
because it provides a three-dimensional overview
of the terrain and indicates human activities as
well as much geologic information to a trained
person.
• In addition, the availability of many types of
aerial imagery (satellite, infrared, radar, and so
forth) makes aerial reconnaissance very versatile
although cost-prohibitive in some cases.

126. Field Reconnaissance
• Many of the more subtle signs of slope movement cannot be
identified on maps or photographs.
• Indeed, if an area is heavily forested or has been urbanized, even
major features may not be evident.
• Furthermore, landslide features change over time on an active
slide.
• Thus, field reconnaissance is always mandatory to verify or detect
landslide features, and to critically evaluate the potential instability
of vulnerable slopes. It identifies areas with past landslides (which
could indicate future likelihood of landslides) by using field mapping
and laboratory testing of terrain through the sampling of soil and
rock.
• Mapping and laboratory testing for example, may identify
vulnerable clays or other susceptible soils and show where they
exist and their size and extent.

127. Drilling
• At most sites, drilling is necessary to determine
the type of earth materials involved in the slide,
the depth to the slip surface, and thus the
thickness and geometry of the landslide mass,
the water-table level, and the degree of
disruption of the landslide materials.
• It also can provide suitable samples for age-
dating and testing the engineering properties of
landslide materials.

128. • Finally, drilling is needed for installation of
some monitoring instruments and hydrologic
observation wells.
• Note that drilling for information on
stratigraphy, geology, water-table levels and
for installation of instruments, for example, is
also done for areas that have never had a
landslide but for which the possibility exists.

129. Instrumentation
• Sophisticated methods such as electronic
distance measurement (EDM), instruments
such as inclinometers, extensometers, strain
meters, and piezometers , and simple
techniques, such as establishing control points
by using stakes can all be used to determine
the mechanics of landslide movement and to
monitor and warn against impending slope
failure.

130. Geophysical Studies
• Geophysical techniques (measurement of soil’s
electrical conductivity/resistivity, or
measurement of induced seismic behavior) can
be used to determine some subsurface
characteristics such as the depth to bedrock,
stratigraphic layers, zones of saturation, and
sometimes the ground-water table.
• It can also be used to determine texture, porosity,
and degree of consolidation of subsurface
materials and the geometry of the units involved.

131. • In most instances, such surface survey methods
can best be used to supplement drilling
information, spatially extending and interpolating
data between boreholes.
• They can also offer an alternative if drilling is
impossible.
• Downhole geophysical methods (nuclear,
electrical, thermal, seismic) also can be applied to
derive detailed measurements in a borehole.
• Monitoring of natural acoustic emissions from
moving soil or rock has also been used in
landslide studies.

132. Acoustic Imagery and Profiles
• Profiles of lakebeds, river bottoms, and the sea
floor can be obtained using acoustic techniques
such as side-scan sonar and sub-bottom seismic
profiling.
• Surveying of controlled grids, with accurate
navigation, can yield three-dimensional
perspectives of subaqueous geologic
phenomena.
• Modern, high-resolution techniques are used
routinely in offshore shelf areas to map geologic
hazards for offshore engineering.

133. Computerized Landslide Terrain
Analysis
• In recent years, computer modeling of
landslides has been used to determine the
volume of landslide masses and changes in
surface expression and cross section over
time.
• This information is useful in calculating the
potential for stream blockage, cost of
landslide removal (based on volume), and
type and mechanism of movement.

134. • Very promising methods are being developed
that use digital elevation models (DEMs) to
evaluate areas quickly for their susceptibility
to landslide/debris-flow events.
• Computers also are being used to perform
complex stability analyses.

135. • Landslide Evaluation Tools— Mapping,
Remote Sensing, and Monitoring of
Landslides

136. Mapping
• Maps are a useful and convenient tool for
presenting information on landslide hazards.
• They can present many kinds and
combinations of information at different levels
of detail.
• Hazard maps used in conjunction with land-
use maps are a valuable planning tool.
• Commonly, there is a three-stage approach to
landslide hazard mapping.

137. • The first stage is regional or reconnaissance
mapping, which synthesizes available data and
identifies general problem areas.
• This regional scale (sometimes called “small-
scale”) mapping is usually performed by a
Provincial, State, or Federal geological survey.
• The next stage is community-level mapping, a
more detailed surface and subsurface
mapping program in complex problem areas.

138. • Finally, detailed site-specific large-scale maps
are prepared.
• If resources are limited, it may be more
prudent to bypass regional mapping and
concentrate on a few known areas of concern.
• We discuss three types of general mapping;
(1) Regional,
• (2) Community level, and
• (3) Site specific.

139. Regional mapping
• Regional or reconnaissance mapping supplies
basic data for regional planning by providing
baseline information for conducting more
detailed studies at the community and site-
specific levels and for setting priorities for future
mapping.
• Such maps are usually simple inventory or
susceptibility maps and are directed primarily
toward the identification and delineation of
regional landslide problem areas and the
conditions under which they occur.

140. • They concentrate on those geologic units or
environments in which additional movements are
most likely.
• The geographical extent of regional maps can
vary from a map of a State or Province to a
national map, which delineates an entire country.
• Such mapping relies heavily on photogeology
(the geologic interpretation of aerial
photography), reconnaissance field mapping, and
the collection and synthesis of all available
pertinent geologic data.
• Map scales at this level are typically at scales
ranging from 1:10,000 down to 1:4,000,000 or
even smaller.

141. Community-level mapping
• This type of mapping identifies both the three-
dimensional potential of landsliding and
considers its causes.
• Guidance concerning land use, zoning, and
building, and recommendations for future site-
specific investigations also are made at this stage.
• Investigations should include subsurface
exploratory work in order to produce a map with
cross sections.
• Map scales at this level typically vary from
1:1,000 to 1:10,000.

142. Site-specific mapping
• Site-specific mapping is concerned with the
identification, analysis, and solution of actual site-
specific problems, often presented in the size of a
residential lot.
• It is usually undertaken by private consultants for
landowners who propose site development and
typically involves a detailed drilling program with
downhole logging, sampling, and laboratory analysis in
order to procure the necessary information for design
and construction.
• Map scales vary but usually are about 1:600 or 25 mm
(1 inch) equal to 16 m (50 feet).

143. Three Important Criteria for Landslide
Maps
• The three types of landslide maps most useful
to planners and the general public are
• (1) landslide inventories,
• (2) landslide susceptibility maps, and
• (3) landslide hazard maps.

144. Landslide inventory maps
• Inventories denote areas that are identified as
having failed by landslide processes.
• inventories that depict and classify each
landslide and show scarps, zones of depletion
and accumulation, active and inactive slides,
geological age, rate of movement, and (or)
other pertinent data on depth and kind of
materials involved in sliding.
• One way is to use aerial photography.

145. Landslide inventory details
• state of activity,
• certainty of identification,
• dominant types of slope movement,
estimated thickness of landslide material,
• type of material, and
• dates or periods of activity.

147. Landslide susceptibility maps
• A landslide susceptibility map goes beyond an
inventory map and depicts areas that have the
potential for landsliding.
• These areas are determined by correlating some
of the principal factors that contribute to
landsliding (such as steep slopes, weak geologic
units that lose strength when saturated or
disturbed, and poorly drained rock or soil) with
the past distribution of landslides.
• These maps indicate only the relative stability of
slopes; they do not make absolute predictions.

148. • Landslide susceptibility maps can be considered
derivatives of landslide inventory maps because
an inventory is essential for preparing a
susceptibility map.
• For example, overlaying a geologic map with an
inventory map that shows existing landslides can
identify specific landslide-prone geologic units.
• This information can then be extrapolated to
predict other areas of potential landsliding.
• More complex maps may include additional
information such as slope angle and drainage.

149. Landslide hazard maps
• Hazard maps show the areal extent of threatening
processes:
• where landslide processes have occurred in the past, recent
occurrences, and most important, the likelihood in various
areas that a landslide will occur in the future.
• For a given area, hazard maps contain detailed information
on the types of landslides, extent of slope subject to failure,
and probable maximum extent of ground movement.
• These maps can be used to predict the relative degree of
hazard in a landslide area.
• Areas may be ranked in a hierarchy such as low, moderate,
and high hazard areas.

150. • Remote Sensing and Other Tools
that Show the Features of
Landslide Activity

151. Techniques to be adopted
• Topographic map: Indicates slope gradient, terrain
configuration, drainage pattern.
• Terrain Map
• Identifies material, depth, geological processes,
terrain configuration, surface and subsurface
drainage, slope gradient (also called surficial
geology or Quaternary geology maps).

152. • Bedrock Map
• Identifies bedrock type, surface and
subsurface structure, surficial cover
(overburden), and age of rock over a
topographic map base.
• Engineering Soil Map
• Identifies surficial material type, drainage,
limited engineering characteristics, soils
characteristics, vegetation cover.

153. • InSAR Imaging InSAR is an acronym for
Interferometric Synthetic Aperture Radar.
• Both InSAR and LIDAR (description follows)
use active sensors emitting a pulse of energy
(from a satellite) and recording its return,
from the ground, at the sensor.
• Most InSAR equipment is able to penetrate
fog and rain and can be used in areas difficult
to access by foot.

154. • LiDAR Imaging LiDAR is an acronym for Light
Detection and Ranging, also known as ALSM
or Airborne Laser Swath Mapping.
• Using a narrow laser beam to probe through
dense ground cover, such as trees, LiDAR can
produce accurate terrain maps even where
forest cover gets in the way of traditional
photography.
• The technique produces a very accurate
Digital Elevation Model map (DEM)

155. Real-Time Monitoring of Landslides
and Landslide Instrumentation
• The immediate detection of landslide activity
that is provided by real-time systems can be
crucial in saving human lives and protecting
property.
• Traditional field observations, even if taken
regularly, cannot detect changes at the
moment they occur.

157. Earth Slope Stabilization/Mitigation
• Removal of soil from the head of a slide
• Reducing the height of the slope
• Backfilling with lightweight material
• Benches
• Flattening or reducing slope angle, or other
slope modification

158. Strengthening Slopes
• Plastic mesh reinforcement
• Rock-fill buttresses
• Stream channel linings
• Check Dams
• Drainage Techniques-Ditches and drains
• Drainpipes
• Retaining Walls, Steel bin wall
• Reinforced earth wall

159. Slope Stabilization Using Vegetation
• Seeding with grasses and legumes reduces
surface erosion, which can under certain
conditions lead to landslides.
• Planting with shrubs adds vegetative cover
and stronger root systems, which in turn will
enhance slope stability.
• Biotechnical Slope Protection

160. Methods of approach
• Forest Cover Map
• Identifies surface vegetation, topographic features,
surface drainage pattern, and in some cases, soil drainage
character.
• Research Studies
• May provide information on all of the above, plus
quantitative data on controlling factors and possibly local
stability risk assessment.
• Aerial Photography Remote Sensing
• Identification can be made of vegetation cover,
topography, drainage pattern, soil drainage character,
bedrock geology, surficial geology, landslide type, and
relationship to other factors.

161. • Landslides and flooding are closely associated
because both are related to precipitation,
runoff, and the saturation of ground by water.
• Flooding may cause landslides by undercutting
banks of streams and rivers and by saturation
of slopes by surface water (overland flow).

162. Rock Slope Stability Analysis: Limit
Equilibrium Method
• • Plane failure analysis
• • Wedge failure analysis
• • Toppling failure analysis
• Stability analysis of slope : circular failure
• Stability Analysis in Presence of Water
•

163. Classification systems in slope
stability analysis
• Slope Mass Rating (SMR)
• Chinese Slope Mass Rating System (CSMR)
• Rock slope rating (RSR)
• Slope stability rating (SSR) classification
system, and
• Dump mass rating

164. Hill slopes
• Hill slopes have a good drainage of rainwater.
• The bed rock configurations are also very
unique.
• The Subsurface Conditions of a hilly terrain
may have two distinct zones as overburden
and the basement rock.

165. • Forest Cover Map
• Identifies surface vegetation, topographic features,
surface drainage pattern, and in some cases, soil drainage
character.
• Research Studies
• May provide information on all of the above, plus
quantitative data on controlling factors and possibly local
stability risk assessment.
• Aerial Photography Remote Sensing
• (Examples shown in figs. B4 through B7.) Identification
can be made of vegetation cover, topography, drainage
pattern, soil drainage character, bedrock geology, surficial
geology, landslide type, and relationship to other factors.

166. RISK MANAGEMENT PROCESS
• The Risk Management process comprises
three components:
• · Risk Analysis
• · Risk Evaluation, and
• · Risk Treatment.

167. HAZARD IDENTIFICATION
• it is important to define:
• The site, being the primary area of interest
• Geographic limits that may be involved in the
processes that affect the site.
• Hazard (landslide) identification requires an
understanding of the slope processes and the
relationship of those
• processes to geomorphology, geology,
hydrogeology, climate and vegetation.

168. Basic documents required
• The basic documents for the hazard evaluation are:
• - Topographical data: Official topographical maps and DEM,
• - Geological data (lithological map),
• - Joint sets
• - Land use planning, existing buildings and other facilities,
• - Thematic maps (rockfall sources, menacing blocks),
• - Event catalogue (derived from chronicles, silent witnesses
in the field and disaster
• documentation),
• - Measurements of the distribution of block sizes at sample
plots of the talus slope.

169. Hazard zoning
• – The subdivision of the terrain in zones that are characterized by
the temporal probability of occurrence of landslides of a particular
size and volume, within a given period of time. Landslide hazard
maps should indicate both the zones where landslides may occur as
well as the runout zones. A complete quantitative landslide hazard
assessment includes:
• • spatial probability: the probability that a given area is hit by a
landslide
• • temporal probability: the probability that a given triggering event
will cause landslides
• • size/volume probability: probability that the slide has a given
size/volume
• • runout probability: probability that the slide will reach a certain
distance downslope
•

170. • Landslide Hazard Zonation: A Case Study in
Garhwal Himalaya, India
• Author(s): S. Sarkar, D. P. Kanungo and G. S.
Mehrotra
• Mountain Research and Development, Vol.
15, No. 4 (Nov., 1995), pp. 301-309

171. Study area

172. Geology and structure

173. Slope

174. Distribution of landslides

175. Statistical Analysis

176. Slope & Landuse

180. Landslide Susceptibility Index

184. LH Zonation map

186. GIS - Links Data Sets
• GIS software links the
location data and the
attribute data:

187. Grid based approach

188. ArcGIS Spatial Analyst Tools

194. Types of
DEMs

196. Triangulated Irregular Network (TIN)

197. A Mesh of Triangles
Triangle is the only
polygon that is always
planar in 3-D
Points Lines Surfaces

198. Tin Triangles in 3-D
(x3, y3, z3)
(x1, y1, z1)
(x2, y2, z2)
x
y
z
Projection in (x,y) plane

200. Flow On a Triangle
2.0
13.0
9.0
10.0
5.0

201. Flow On a TIN
50
60
70
80
90
100
110
120
50
60
70
80
90
100
110
120
50
60
70
80
90
100
110
120
50
60
70
80
90
100
110
120
50
60
70
80
90
100
110
120

202. Conceptual Model
Triangulate
Enforce Breaklines
Interpolate Z
5: Create TIN

203. Defining Basins

204. Computing Basin Data
• Area
• Slope
• Flow Distances
– Slopes
• Aspect
• Stream Lengths
– Slopes
• Others
A=3.18 acr
BS=0.0124 ft/ft
AOFD=140.06 ft
A=5.39 acr
BS=0.0243 ft/ft
AOFD=158.33 ft
A=7.21 acr
BS=0.0200 ft/ft
AOFD=93.47 ft

205. • Landslide susceptibility map – A map showing
the subdivision of the terrain in zones that have a
different likelihood that landslide of a type may
occur. The likelihood may be indicated either
qualitatively (as high, moderate low, and not
susceptible) or quantitatively (e.g. as the density
in number per square kilometres, or area affected
per square kilometre). Landslide susceptibility
maps should indicate both the zones where
landslides may occur as well as the runout zones.

206. Various approaches used
in GIS modeling

209. Analyze Landscape Structure

210. Use Statistics to Compare Map
Surfaces

211. Identifying Convex and Concave features by
deviation from the trend of the terrain

212. Example of a micro-terrain deviation
surface

213. Calculation of slope considers the arrangement
and magnitude of elevation differences within a
roving window

214. Longitudinal slope calculates the steepness
along a linear feature, such as a pipeline

215. Modified transverse slope is calculated as the average
of off-route slopes surrounding a location

216. Analyzing the slope differences along
a proposed route

217. 2-D, 3-D and draped displays of
terrain roughness

218. Map of surface flow confluence

219. 2-D, 3-D and draped displays of
surface flow confluence

220. Identifying Upland Ridges

221. A simple erosion potential model combines
information on terrain steepness and water
flow confluence

222. Extended erosion model considering sediment
loading potential considering intervening
terrain conditions

223. Gentle slopes surrounding streams are visually
apparent on a 3D plot of elevation

224. Slope values for the terrain surface are
calculated and gently sloped areas identified

225. Valley bottoms are identified as flat
areas connected to streams

226. Use Surface Area for Realistic
Calculations

227. Visual comparison of different slope
maps

228. Comparison of Fitted versus
Generalized slope maps

229. GIS Modeling

231. PURPOSE OF LANDSLIDE ZONING
MAPS
• Landslide zoning may be developed by preparing
different maps that, according to the type of
zoning, can be distinguished among (see also the
definitions given Chapter 2):
• • Landslide inventory map;
• • Landslide susceptibility zoning map;
• • Landslide hazard zoning map;
• • Elements at risk map;
• • Consequence scenario map;
• • Landslide risk zoning map.

232. • Landslide inventory map may be used for
susceptibility zoning and/or as information for
policy makers and the general public;
• • Landslide susceptibility zoning map may be
used to prepare the hazard map and/or, in
combination with elements at landslide risk
within the susceptible area, as information for
policy makers and the general public. It may be
also used as advisory where the available records
of incident data allows the assessment of the
societal risk (e.g., in terms of F-N curves) within
the susceptible areas threatened by rapid to
extremely rapid landslides (Cruden and Varnes,
1996);

233. • • Landslide hazard zoning map can be used as
information, advisory or statutory to control the
development of threatened areas, representing
the most efficient and economic way to reduce
future damage and loss of life. Such maps also
provide the appropriate element of decision for
considering the feasibility of the development
with or without any stabilisation or protective
countermeasures (Cascini et al., 2005);
• • Elements at risk map is used to prepare the
consequence scenarios map and, in combination
with the landslide susceptibility zoning map, may
be used as information and advisory for policy
makers and general public;

234. • • Consequence scenario map may be used as information
and advisory showing the areas that require QRA. Using
quantitative procedures, this map provides for each
element the consequence scenario related to its
vulnerability and a given landslide hazard; in such a case, it
may be used as information, advisory and statutory.
• • Landslide risk zoning map may be used as statutory and
allow the implementation of alert system aimed at
protecting the human life. In addition, QRA provides a
global view of the expected annual damage for the
elements at risk due to the landslide hazard. It can be used
as statutory and design and, on the basis of cost-benefit
analysis, either control or stabilization works can be
identified and designed for landslide risk mitigation.

235. ANALYSIS FOR LANDSLIDE HAZARD
ZONATION:-
• Digital Elevation Model (DEM)
• Digitized contour map
• Elevation sliced map
• Slope map in degree
• Slope aspect map
• Flow direction map
• Flow accumulation map
• Village Map/ Road Map

236. • Google Earth Data
• Land Cover Map
• Lithology Map

237. A landslide hazard zonation map
• is prepared to assist mitigation planners in wake of landslide trigger.
In the present study pre and post earthquake remote sensing data
has been used to prepare landslide inventory.
• Remote sensing data is further used to delineate drainage pattern,
photo lineaments, structural features, lithologial features, and
land/use land/cover type of the area by applying digital image
processing techniques.
• Geological features are analyzed using criteria such as colour, tones,
topography and stream drainage pattern from the imageries.
• Digital elevation model data is used to generate primary
topographic attributes namely, slope, aspect, and relative relief.

238. • For landslide hazard zonation (LHZ) different thematic maps
such as land-cover map, slope map, relative relief map,
structural map, lithology map, lineament buffer map,
drainage buffer map, soil map, are assigned relative weight
on ordinal scale to obtain landslide hazard index (LHI).
• Threshold values are selected according to breaks in LHI
frequency and a LHZ map is prepared which contains very
low hazard, low hazard, moderate hazard, high hazard and
very high hazard zones.
• Study suggests that landslides in present area are
influenced by the proximity to drainage, lineament and
topographic attributes

239. • Landslides are triggered by many extrinsic
causative factors such as rainfall, earthquake,
blasting and drilling, cloudburst and
flashfloods. Himalayan region has highly
undulating terrain which is a witness of
ongoing orogeny process.

241. WEIGHT ANALYSIS
• Weighted rating system is based on the relative
importance of various causative factors derived
from field knowledge.
• Input data layers such as soil map, lineament
buffer map, slope map etc. are assigned
weightage (out of total 100%) factor according to
their corresponding impact on the landslide
triggers.
• Different classes of input layers are given rating
on the scale of 1 to 10 where 1 stands for the
class which has minimum impact on landslide.

242. Landslide Hazard Index
• is prepared by assigning influence/weight to
factor and rating to different classes. Weight
factor of the input layer is multiplied by the
corresponding rating given to that particular
class on pixel basis.
• Finally summation of each layer is done.
• LHI = Σ Weight/influence of factors× ratings of
classes/attributes

243. SUMMERY OF ASSIGNED WEIGHT AND
RATING

247. GIS Lanslide Susceptibility Model in
ArcGIS Model Builder

251. Ground Penetrating Radar

252. GPR

253. Lidar can show the

264. Lidar + GIS: Revolutionizing Landslide
Mapping and Field Evaluation