Topic 1: Physical Features

Question 1

What is Topography?

Answer 1

Topography is the arrangement of natural physical features of an area. It is defined by a land surface’s reliefs, contours, mountains, valleys, rivers, & flood plains.

Question 2

What are 3 natural distinctive features of BD?

Answer 2

o Uplands – a slightly elevated relatively older plain
o Hills – a small hill region drained by fast-flowing rivers
o Flood plain – a broad alluvial plain subject to frequent flooding

Question 3

State some examples of Uplands/Terraces in BD.

Answer 3

 Barind Tract (Rajshahi)
 Madhupur Tract (Dhaka & Mymensingh)
 Tippera Surface (Comilla)

Question 4

State some examples of Tertiary Hills in BD.

Answer 4

 Low hills (Sitakunda Peak)

 High hills (CHT)

Question 5

State some examples of Floodplains in BD.

Answer 5

 Deltaic plains (Khulna, north of Barisal)

 Coastal plains (coast of Khulna, Chittagong, Barisal)

Question 6

State the physical features of Uplands/Terraces.

Answer 6

 Formed by sediments which come from flood of snow-melt from Himalayas
 Formed like terraces
 Slightly undulating
 Alluvial/ Clay
 Oxidized sediments
 Soil color is yellowish to red
 Formed by dendritic drainage pattern of Padma & Jamuna River
 Average elevation is more than 15 m above the mean sea level (MSL)
 Landform is 2.5 million years old from when mammoths lived

Question 7

State the physical features of Tertiary Hills.

Answer 7

 Formed at the same time when Himalaya formed
 Height is 600 m to 1300 m above the MSL
 Comprised of eroded valley and isolated hillocks
 Have steep slopes with landslides
 low hills and high hills
 Keokaradang 1,230 m/ high peak / other named peak e.g. Sak-Haphong
 Lakes: Rainkhiangkine, Bagakine, Kaptai
 Animals: snakes / monkeys / jungle cats / wild boar / foxes / abundant birdlife
 Soil: brownish loam & very acidic
 Climate: Tropical monsoon / heavy rain

Question 8

State the physical features of Flood Plains.

Answer 8

 Cover 90% of Bangladesh
 Flooded during monsoons
 Formed mostly along the main river channels
 Very fertile, cultivable land to grow any types of crops
 Featured with yearly deposition & erosion of rivers
 Still contributing to form 60% of the coastline
 Presence of mangrove where there is saline soil

Question 9

State the physical features of Deltaic Plains.

Answer 9

	Flat
	Old delta
	Sediments/alluvium/silt deposited on sea floor/river mouth/fertile soil
	W is inactive - relatively old
	E is active - relatively young
	Dissected by river channels

Question 10

State the physical features of Coastal Plains.

Answer 10

 Relatively rapid changes in landforms due to erosion and sedimentation have occurred in the coastal areas
 The coastal areas with mangrove plantations are regularly inundated during high tide
 Soil ranges from silty loam to silty clay loam

Question 11

State the physical features of Valley/Plains.

Answer 11

 Gently sloping land at the foot of hills
 Formed with alluvial sediments deposited by rivers or streams.
 Covered by Piedmont sands and gravel

Question 12

State the Human features of Uplands.

Answer 12

 Many different crops are grown. So, mostly agro-based industries are flourished in Khulna or Rajshahi
 Uplands are flatlands so less chances to be affected by natural calamities.
 Densely populated area by BD
 Ideal crops are drought-resistant & Rabbi crops

Question 13

State the Human features of Hills.

Answer 13

 Less populated area. So, few human settlements
 Mostly best for Jhum cultivation and tea garden
 Ideal place for ethnic people (Chakma, Marma, etc.) to live

Question 14

State the Human features of Flood Plains.

Answer 14

 Fertile land but affected by flood annually
 Easy communication by river so created the second most densely populated are of Bangladesh
 Ideal crops are drought-resistant & Kharif crops

Question 15

What is a deltaic plain?

Answer 15

A deltaic plain consists of active or abandoned deltas, which are either overlapping or continuous to one another.

Question 16

What is a coastal plain?

Answer 16

A coastal plain is a flat, low-lying piece of land next to the ocean. Coastal plains are separated from the rest of the interior by nearby landforms, such as mountains.

Question 17

State the meaning of a drainage basin.

Answer 17

The area of land drained by a single river.

Question 18

What is a drainage system?

Answer 18

A drainage system consists of patterns formed by streams, rivers, and lakes in a drainage basin.

Question 19

What is river discharge?

Answer 19

River discharge is the volume of water flowing through a river channel per second

Question 20

What is a river’s load?

Answer 20

A river’s load is bits of eroded material, generally rocks, that the river transports until it deposits its load.

Question 21

What are the 5 major river systems?

Answer 21

o	Brahmaputra-Jamuna River system
o	Ganges-Padma River system
o	Surma-Meghna River system
o	Tista river system
o	Karnaphuli river system

Question 22

Name the large rivers which join together to form the Bengal Delta?

Answer 22

o Ganges-Padma
o Brahmaputra-Jamuna
o Meghna

Question 23

Where do rivers enter BD?

Answer 23

o near Chittagong – Karnaphuli &
o near Rajshahi – Gange,
o near Rangpur – Tista

Question 24

Are the rivers of Bangladesh in the upper, middle or lower course? Why?

Answer 24

Rivers of Bangladesh are in lower course. Because:

1. Slow moving flow of river water
2. More deposition & moving towards Bay of Bengal
3. It is still creating active delta.
4. Rivers have tributaries, distributaries & dendritic drainage pattern

Question 25

What are the meandering rivers of BD?

Answer 25

Ganges, Meghna, rivers of Barind Tract area e.g., Karatiya, Gorai

Question 26

Explain how meanders are formed.

Answer 26

1. Rivers tends to remove irregularities & forms a smooth gradient from it source to base level. 2. As it approaches to base level, vertical erosion is replaced by lateral erosion 3. The rivers widen its bed & valley, develops a spiral course, from the gradual erosion and deposition of river water. 4. On the inside of the bank (inner bank), where river flow is slow, materials deposited forms slip of slopes. 5. Outer bank of the river erodes and forms river cliffs. 6. As a result, it forms loops & bends, called meander.

Question 27

State the importance of Meanders.

Answer 27

o Rivers erode and change its courses due to meanders. | o Meanders creates sediments which enhances the inner bank of the rivers.

Question 28

What is an Oxbow Lake?

Answer 28

An oxbow lake is a shallow crescent shaped lake formed from a meandering river.

Question 29

How are Oxbow Lakes formed?

Answer 29

1. In a meandering river at middle course, in the outer bank, there will be erosion & in the inner bank, there will be deposition 2. A pronounced meander will create. Meander neck becomes narrower with deposition. 3. In times of flood river flows straight & breaks at neck of meander 4. Deposition seals off the meander neck & creates a crescent shape lake, called ox-bow lake.

Question 30

What is a Flood Plain?

Answer 30

o Wide area of flat, low-lying land either side of a river channel. o It is formed by meanders migrating downstream o composed of alluvium deposited by repeated flooding.

Question 31

How are Flood Plains formed?

Answer 31

1. Meandering river migrates downwards. 2. At high discharge, river caries large amount of materials. 3. When a river floods, it overflows its banks. 4. Sediments (rich alluvium) are deposited by floodwaters 5. Repeated flooding causes the sediments to permanently settle down on the banks of river. 6. A flood plain is formed

Question 32

What is a Levee? Give Example.

Answer 32

A buildup of alluvium on the banks of a river can create levees, which raise the river bank. • Examples: Dhaka City is located on the natural levee of the river Buriganga

Question 33

How are Levees formed?

Answer 33

1. When floodplains are formed, the heaviest materials like rock, boulders are deposited near the banks of river. 2. Repeated flooding results the growth of coarse silt on the edges of river. 3. After successive floods, natural embankments called levees are formed along the two river banks. 4. This is called levees which are created alongside the river.

Question 34

What is a Braided Stream? Give Example.

Answer 34

A braided stream has multiple channels separated from each other by small and temporary islands called bars. It is characterized by a network of constantly shifting channels around channel sandbars. • Example: The Brahmaputra-Jamuna in Bangladesh is one of the world’s largest braided rivers.

Question 35

How are Braided Streams formed?

Answer 35

1. In lower course, channel has shallow depth of water & less friction. 2. No longer able to carry load. 3. Channel is blocked by deposition and splits into smaller channels.

Question 36

What is a Delta? Give Example.

Answer 36

A delta is a low-lying area of land formed at the mouth of a river where the stream loses velocity and drops part of its sediment load. • Example: The Bengal Delta is a compound delta (Brahmaputra & Ganges) o Divided into moribund, active, immature, mature deltas.

Question 37

How are Deltas formed?

Answer 37

1. Heavy load such as silt, alluvial soil, carried by river forms a delta. 2. Forms in the mouth of the river towards a sea. 3. Deposition occurs as the river loses velocity when it enters the sea 4. Distributaries form as the main river channel splits into smaller channels 5. Gradual deposition helps to spread the delta and forms distributaries. 6. No currents/strong tides to remove deposition 7. Advances towards the sea