Transcript Physiographic Classification

3.2 Relief & Physiography (elevation of
various regions of BD from the sea level,
three major classification of physiographic
features)
Relief & Physiography
• Bangladesh is crisscrossed by a larger number of
rivers maintaining an intricate network with their
numerous tributaries & distributaries.
• The elevation in the major part of BD is low since the
most of the country’s land is originated through fluvial
processes.
• Nearly 50% of the country’s elevation is less than 10
m from sea level.
• The southeastern hilly region exceeds an elevation of
300 meters.
• Around 20% of the land consists of low-lying tidal plain
having an average elevation of 3 m above the sea level.
Physiography
Physiographic Classification
• Most of the deltaic southern part of the Bengal
Basin is not more than 10,000 years old (Rashid,
1991).
• Based on the age & formation of landmasses, the
physiography of BD can be divided into three
categories• a) Hills (Tertiary period) b) terraces (Pleistocene
age) & c) flood plains (relatively recent) .
Physiographic Classification
• Hills: developed in Tertiary period (35-15 m yrs
ago) occupying 12% of the land area
-located mainly in the southeastern regions of Ctg &
CHTs and northern part of great Sylhet District.
-topography is largely determined by geologic
structure (folded, faulted & uplifted) & rock type
(sandstone, siltstone & shale of mid-Tertiary age).
Physiographic Classification
•Terraces
-major terraces are the Barind (located in Rajshahi,
Dinajpur & Bogra districts with an area of around 8000
sq km) & Madhupur Tracts are located in the
northwestern & central parts of BD respectively.
-Lalmai (with an area of 33 sq km), west of Comilla
Town is also a smaller terrace.
-These terraces cover 8% of the land which are also
recognized as OLD ALLUVIUM (flood plain deposits of
the earlier Ganges & Brahmaputra rivers).
-the Madhupur Tract extends from north of Dhaka in the
south to Jamalpur & Mymensingh to the north with an
area of around 4000 sq km.
Physiographic Classification
• Flood plains
-are also known as alluvial plains through fluviodeltaic processes.
-flood plains are created due to the deposition
(alluvium) of the GBM rivers covering 80% of the
land in Bangladesh.
-there are as many as 9 types of flood plains in BD,
of which the Ganges plains cover a major part.
BANGLADESH:
Physiographic Unit
Ref. (Rasheed,
2008)
Flood Plains
1 Old Himalayan Floodplain
2. Teesta Floodplain
3. Brahmaputra Jamuna Floodplain
4. Ganges Floodplain
5. Meghna Floodplain
6. Surma-Kushiara Floodplain
7. Ganges Tidal Floodplain
8. Meghna Estuarine Floodplain
9. Ctg coastal Floodplain
1
Old Himalayan
Piedmont Plain
2
2
Teesta Floodplain
2
2
3
Meghna
3
3
Brahmaputra-Jamuna
Floodplain
3
4
4
Ganges Floodplain
4
4
4
5
5
5 Meghna Floodplai
6
Surma Kushira
Floodplain
7
Ganges Tidal
Floodplain
8
Meghna Estuarine
Floodplain
8
8
8
9
9
Ctg Coastal plain
Physiographic Classification
• Subdivisions of Delta
1. Moribund delta
2. Immature Delta
3. Active Delta
4. Mature Delta
1
3
2
4