Due to its geographical location, Chittagong city suffers from numerous natural disasters like landslide, water logging, cyclone, flood etc. But at present landslides are the most burning issues in respect of Chittagong City Corporation (CCC) area. Because Chittagong hills are degrading by different anthropogenic stress such as hill cutting for construction, sand and clay mining purpose, increasing settlement in foothills, deforestation which are very much responsible for landslide occurrences.

1. Geomorphology of landslide
in Bangladesh

2. Due to its geographical location, Chittagong city suffers from numerous natural
disasters like landslide, water logging, cyclone, flood etc.
But at present landslides are the most burning issues in respect of Chittagong City
Corporation (CCC) area.
Because Chittagong hills are degrading by different anthropogenic stress such as hill
cutting for construction, sand and clay mining purpose, increasing settlement in
foothills, deforestation which are very much responsible for landslide occurrences.
Date Location Consequence
3 August 2005 Nizam Road Housing Society 2 people killed and 12 injured
11 June 2007 Mati Jharna Colony of Lalkhan Bazar
10 September 2007 Nabi Nagar in Chittagong 2 people killed
18 August 2008 Matijharna in Chittagong 11 people killed and 25 injured
26 June 2012 Lebubagan Area and Foy‟s Lake 90 people killed and 150 injured
01 July 2011 Batali hill, Tiger pass intersection 15 people killed and 150 injured
28 July 2013 Lalkhan Bazar 2 people killed
Summary of the crucial landslide incidences

3. Geomorphology of Chattogram Region
The city, under the jurisdiction of
City Corporation, has a
population of about 2.5 million,
is constantly growing with an
area approximately 155 square
kilometers (CDA, 2014). The
city lies 21°54 minute north to
22°59 minute north latitude and
91°17 minute east to 92°14
minute east longitude and extend
north bank of the Karnafuli river
to west bank of the Halda River.
Chittagong is the second largest
city of Bangladesh where the
largest sea port is located, which
is one of the backbones for the
economy of the country. The
highest ground level within the
city area is about 60m above.

4. Landslide inventory map Land cover map
Landslide inventory is an essential
part and basic information for any
landslide zoning such as
susceptibility, risk and hazard
zonings. A total of 20 landslide
locations are identified in the study
area through field survey and the
latitude and longitude values are
collected using a Hand GPS device
Land cover maps represent spatial
information on different types
(classes) of physical coverage of the
Earth's surface, e.g. forests,
grasslands, croplands, lakes,
wetlands etc.

5. Normalized Difference Vegetation
Index (NDVI) map
Slope Map
The normalized difference
vegetation index (NDVI) is
developed from the reflective bands
of Landsat 8 satellite data for
estimating available type of
vegetation cover
Slope maps are isoline (lines of equal value)
maps of selected slope categories. To construct
a slope map we must select
specific slope categories to map and know the
scale of the map and the contour interval.
Generally steeper slope is more susceptible to
landslide but most of the observed landslide
occurrences in Chittagong were found within a
slope range from 15-45 degrees

6. Aspect map Elevation map
The aspect represents the down slope
direction of the maximum rate of
change in value from each cell to its
neighbors. Slope facing south,
southwest, west receive maximum
rainfall in Chittagong region. Any
slope faces maximum rainfall is more
susceptible to landslide than others
An elevation map is any map which shows the
different elevations of an area. The elevation map
has been prepared from the DEM layer where the
relative height of the layer is considered. Higher
elevation is characterized by compacted
sandstone in Chittagong city which is also
resistance to sliding activity but moderate elevation
of 8-12 m have also high susceptibility for landslide
occurrences

7. Distance to road Distance to water body
Landslides may occur on the road
and on the side of the slopes
affected by roads. The distance
from road classes closer to the
road covered the higher percentage
of landslide area while the classes
far from the road had lowest
percentage of landslide
The area closer to the river and
stream has high level of
landslide. Euclidean distance is
also used to prepare distance to
water body layer map at 200
meter intervals

8. Drainage density Geology and Geomorphology
Drainage density is the total length of
all the streams and rivers in a drainage
basin divided by the total area of the
drainage basin. It is a measure of how
well or how poorly a watershed is
drained by stream channels. DEM data
is used to prepare Drainage density.
Geology and Geomorphology data
are collected from Geological
Survey of Bangladesh (GSB).The
highest preference are given to
the geologic formations of slope
and valley deposit where
majority of landslides had
previously occurred

9. Precipitation/ Rainfall Pattern
Due to climate change, CCC is experiencing high intensity of
rainfall in recent years which is making the landslide
situation worse.
Previous ten years of precipitation data has been collected
from Bangladesh Metrological Department and the average
daily precipitation of the whole CCC area is more of less same.

10. Morphology of Landslides
Before we discuss about different types of landslides, it
would be good to learn about the morphology of landslides
and its various features/parts as given below

11. Parts of Landslides – Description of
Features
• Accumulation - The volume of the displaced material,
which lies above the original ground surface
• Crown – The practically un displaced material still in
place and adjacent to the highest parts of the main scarp
• Depletion – The volume bounded by the main scarp, the
depleted mass and the original ground surface
• Depleted mass – The volume of the displaced material,
which overlies the rupture surface but underlies the
original ground surface.
• Displaced material – Material displaced from its
original position on the slope by movement in the
landslide. It forms both the depleted mass and the
accumulation.

12. Parts of Landslides – Description of
Features
• Flank – The un displaced material adjacent to the sides of the
rupture surface. Compass directions are preferable in
describing the flanks, but if left and right are used, they refer
to the flanks as viewed from the crown.
• Foot – The portion of the landslide that has moved beyond
the toe of the surface of rupture and overlies the original
ground surface.
• Head – The upper parts of the landslide along the contact
between the displaced material and the main scarp.
• Main body – The part of the displaced material of the
landslide that overlies the surface of rupture between the
main scarp and toe of the surface of rupture.
• Main scarp – A steep surface on the undisturbed ground at
the upper edge of the landslide, caused by movement of the
displaced material away from undisturbed ground. It is the
visible part of the surface of rupture.

13. Parts of Landslides – Description of
Features
• Minor scarp – A steep surface on the displaced
material of the landslide produced by the differential
movement within the displaced material.
•
• Original ground surface – the surface of the slope
that existed before the landslide took place.
• Surface of separation – The part of the original
ground surface overlain by the foot of the landslide
• Surface of rupture – The surface that forms the lower
boundary of the displaced material below the original
ground surface.
• Tip – The point of toe farthest from the top of the
landslide.

14. Parts of Landslides – Description of
Features
• Toe – The lower, usually curved margin of the displaced
material of a landslide, it is the most distant part from the
main scarp.
• Top – The highest point of contact between the displaced
material and the main scarp.
• Toe of surface of rupture – The intersection (usually
buried) between the lower part of the surface of rupture of a
landslide and the original ground surface.
• Zone of accumulation – The area of landslide within which
the displaced material lies above the original ground surface.
• Zone of depletion – The area of the landslide within which
the displaced material lies below the original ground surface.