Physical Setting Of Nigeria: Relief And Drainage SS1 Geography Lesson Note

Relief refers to the surface features of the land above the sea level. The relief of Nigeria can be grouped into two main classes. These are lowlands and highlands.

1. LOWLANDS: These are areas below 300m above the sea level. Areas of lowlands in Nigeria include the following:

i. The Sokoto Plain (200  300m)

ii. The Niger  Benue Trough / Valley (100  300m)

iii. The Chad Basin or Bornu Plain

iv. The Niger Delta (0  100)

v. The Cross River Basin (120  180)

vi. The Coastal Plain (0  100)

vii. The interior coastal lowland of western Nigeria (100  300m)

ROCKS ASSOCIATED WITH LOWLANDS

(i) The coastal plain: Sedimentary rocks of alluvial deposit.

(ii) Niger Benue Trough: Sedimentary rocks such as limestone, sandstone and shale.

(iii) Sokoto plain: Sedimentary rocks like sand, clay, sandstone and limestone.

(iv) Chad basin: Sedimentary rocks of sand and clay.

Rocks generally known to be associated with lowlands are sedimentary rocks.

IMPORTANCE OF LOWLANDS

i. Plains, especially level ones, are good for human habitation. Population and settlement are usually concentrated on plains

ii. Some plains are rich sources of minerals like petroleum, coal, etc.

iii. Plains, especially depositional plains are very fertile for agriculture.

iv. Plains, since they are level, favor communication roads, railways, and airports.

v. Rivers and plains (basin) providers.   g fishing.

vi. Rearing of animals is also better done on level grounds.

vii. Some plains have rivers which provide water for so many purposes.

DISADVANTAGES OF PLAINS

1. Some plains especially in delta areas may be flooded with water. Flooding is an environmental hazard.
2. Some plains may pose a serious barrier to communication, especially in flooded areas.

2. HIGHLANDS: These are areas that are over 300m above the sea level. Areas of highlands in Nigeria and their height include the following:-

(i) The North-Central highlands

(ii) The Western Highlands 

(iii) The eastern Highlands

(iv) The Eastern scarpland 

1. THE NORTH-CENTRAL HIGHLANDS

This lies in the centre of Northern Nigeria around Kano, Kaduna Bauchi, Jigawa and Plateau State. The most important highland in these areas is the Jos Plateau (200  1500m). Rivers like Hadeija, Kaduna, and Sokoto etc. take their sources from Jos Plateau. The highest point of Jos Plateau is Shere Hills (1650m).

    2. THE WESTERN HIGHLANDS

This is found in the Western part of Nigeria around Ondo, Oyo, Kwara, and Osun State. Important hills in this area include the following:-

1. a) Idanre hill (950m)
2. b) Apata hill (400 – 700m)
3. c) Epeme hill (350  600m)

Three important rivers have their sources from these highlands. They are the rivers Ogun, Osun and Osse.

   3. THE EASTERN HIGHLANDS

This is found on the border between Nigeria and Cameroon. They have the highest mountain in Nigeria. They include:-

1. a) Mandara Mountain (1200 – 1500)
2. b) Biu Plateau (800 – 1000m)
3. c) Adamawa Mountain (1800 – 2400m)
4. d) Alantika and Shebshi Hills (1600 – 2000m)
5. e) Obudu and Oban hills (1200m)

Rivers found in these areas are River Gana, Ngodo and Yedseram which flow to Lake Chad.

4. THE EASTERN SCARPLAND 

This is found within the eastern region, especially The only major highland found in this area is the Udi Nsukka plateau (300  600m). Important rivers include Anambra, Imo and Cross River.

ROCKS ASSOCIATED WITH HIGHLAND

(i) North Central Plateau, Western highland, Mandara Mountain, Shebshi, Alantika, Obudu and Oban hills are made up of basement complex rocks (a combination of igneous and metamorphic rocks).

(ii) Jos plateau is made up of volcanic rocks.

(iii) Udi hills are made up of Carboniferous sedimentary rock.

IMPORTANCE OF HIGHLANDS

1. Sources of minerals.
2. Formation of rainfall, especially orographic rainfall.
3. It is used for defence in times of war.
4. It serves as Windbreaks.
5. They are a good source of rivers.
6. The rivers provide a site for the Hydro-Electric Power (HEP).
7. They provide tourist centres.
8. They are used for transhumance.

DISADVANTAGES OF MOUNTAINS

1. communication erosion.
2. Mountains occupy good land that would have been used for other purposes.
3. They prevent human habitation.
4. Mountainous soils are poor in nutrients and are not good for agriculture.

NIGERIA: DRAINAGE

Drainage refers to water bodies like rivers and lakes.

RIVERS IN NIGERIA

Nigeria is drained by two main rivers  River Niger and River Benue. River Niger is the largest river in Nigeria and it has its source from the Guinea highlands in Guinea. It passes through Mali and Niger Republic to Nigeria and the Atlantic Ocean anan.

River Benue has its source from the eastern highlands and joins River Niger at Lokoja. Lokoja, because of this, is known as a confluence town. Other rivers in Nigeria take their sources from highlands n as Hydrological centres. These are:

(i) Western Highlands: They have rivers such as Ogun, Osun and Osse.

(ii) North-Central Highlands: They have rivers such as Kaduna, Hadeija, Zamfara, Yobe, Gana, Gongola and Rima.

(iii) Eastern Highlands: They have rivers such as Donga and Katsina-Ala.

(iv) Eastern Scarplands: They have rivers like Anambra and Cross River.

CHARACTERISTIC OF NIGERIAN RIVERS

1. The volume of the rivers changes with seasons. It increases during the rainy season and reduces during the drying season.
2. Presence of rapids cataracts. This impedes inland navigation.
3. Presence of debris like dead leaves, mud, wood, etc.
4. Short courses with high speed.
5. Specific direction of flow. Rivers in the south flow in the north-south direction while rivers in the north flow in a radial pattern in different directions.
6. Shallowness.
7. The colour changes with the season.
8. Seasonality: Most rivers flow during the rainy season and stop or reduce flowing to flow during the dry season.

IMPORTANCE OF NIGERIA RIVERS

1. Medium of transportation.
2. Generation of Hydro-Electric Power (H.E.P).
3. Irrigation purposes.
4. Domestic uses.
5. Industrial uses.
6. Provision of employment.
7. Recreation/Tourism.
8. Source of food supply (fishes, etc).

RIVER BASIN

River basin refers to the area generally drained by a river. The River basin is also known as the catchment area. In Nigeria, there are five major river basins. These are:-

(i) The Niger basin

(ii) The Benue basin 

(iii) The Chad basin

(iv) The Cross River basin 

(v) The South Atlantic basin

The rivers in these basins are grouped into 3 classes:

1. Long rivers with large basins e.g. River Niger and Benue.
2. Short rivers with small basins e.g. River Osun, Ogun, Cross River etc.
3. Rivers in basins of inland drainage: These are rivers that do not reach the sea but rather flow into Lake Chad. Examples are River Yobe, Hadeija, Gana and Yedseram.

IMPORTANCE OF RIVER BASIN

1. Good site for settlement.
2. Provision of suitable lands for agricultural purposes.
3. Medium of communication due to the presence of rivers.
4. Presence of some mineral deposits.
5. Provision of water.
6. Provision of sites for fishing.

LAKES IN NIGERIA

A lake is a body of water surrounded by land. The lakes are grouped into two major types:

1. Man/Made or Artificial lakes: They are lakes constructed by man e.g. lake kanji river Niger and Shiroro Lake on River Kaduna.
2. Natural lakesakes which exist naturally e.g. Lake Chad.

ASSIGNMENT

1. Lowlands refer to places that are below ________ above the sea level.  (a) 800m (b) 500m (c) 300m (d) 100m

2. The rock types found in most  is  (a) Igneous rocks (b) Sedimentary rocks (c) Metamorphic rocks (d) calcareous rock
3. Which of these hills is found in the Eastern Scarpland (a) Idanre Hill b) Apata Hill (c) Oban Hill (d) Udi Hill
4. Which of these rivers is sourced from the North-Central highlands    (a) Imo  (b) Ogun (c) Hadeija (d) Osse

5. Which of these hills is composed of volcanic rocks (a) Jos Plateau (b) Epeme hill (c) Udi hill (d) Mandara hill

6. List three importance of lowlands.

7. Write one natural lake and one artificial lake.