Nigeria Physical Setting: Relief and drainage

Subject: Geography Week 8

 Class: SS1

Topic: Nigeria Physical Setting: Relief and drainage

Specific Objectives: By the end of this lesson the students should be able to;

1. Identify major highlands in Nigeria
2. Identify the major lowlands in Nigeria
3. Identify the Rivers/drainage systems in Nigeria
4. State the characteristics of a river
5. Mention the importance rivers

RELIEF (LOWLANDS AND HIGHLANDS)

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

Lowlands: Lowlands refer to the areas below 300m above sea level.

Areas of lowlands in Nigeria: Areas of lowlands in Nigeria and their altitudes or heights are as follows:

1. The Sokoto plain in the North West (200-300m)
2. The Niger-Benue trough/valley (100-300m)
3. The Chad Basin or Bornu plain (100-300m)
4. The Niger-Delta (0-100m)
5. The Cross River Basin (120-180m)
6. The interior coastal lowland of Western Nigeria (100-300m)
7. The coastal plain (0-100m)

Rocks associated with lowlands

1. Coastal plain – Sedimentary rocks of alluvial deposits
2. Niger-Benue trough – sedimentary rocks of limestone, sandstone and shale
3. Sokoto plain – sand, clay, sandstone and limestone
4. Chad basin – made up of sand and clay

Importance of lowlands

1. Plains, especially level ones are good for human habitation. Population and settlements are usually concentrated on plains
2. Sources for rich mineral resources like petroleum and coal
3. Depositional plains have rich fertile soils for agriculture
4. Plains favour communication as roads, railways, airports are better built on level lands
5. Rivers in plains provide water for domestic purposes and transportation
6. Plains are good for rearing of animals in areas of low rainfall

Highlands: Highlands refer to areas over 300m above sea level

Areas of Highlands in Nigeria: The highlands in Nigeria are grouped into four areas;

1. The North-Central Highlands: It lies in the centre of Northern Nigeria around parts of Kano, Kaduna, Bauchi, Jigawa and Plateau states. Jos plateau (200-1500m) is found in this highland and it is a Hydrological centre or watershed with radial pattern of drainage in which rivers like Hadeija, Kaduna and Sokoto take their sources. The highest point of Jos plateau is the Shere Hills (1650m)
2. The Western Highlands: The Western highland or upland is found in the western part of Nigeria around Oyo, Ondo, Kwara and Osun states. Some of the important hills in the area are; Idanre hill (950m) which is the highest point, Apata hill (400-700m), Epeme hill (350-600m). Rivers Ogun, Osun and Osse have their sources from these highlands.
3. The Eastern Highlands: These are found in the borders between Nigeria and cameroun. They represent the highest zone in Nigeria. Among them are; Mandara mountain (1200-1500m), Biu plateau (800-1000m), Adamawa mountain (1800-2400m), Alantika and Shebshi hills (1600-2000m), Obudu and Oban hills (1200m). The rivers in these areas are  Gana, Ngoda, Yedseram which flows to lake Chad.
4. The Eastern scarp-land: This is found within the South eastern region og Nigeria, especially around Enugu and Nsukka. The major highland in this area is the Udi-Nsukka plateau (300-600m). Rivers Omanbala, Imo and Cross have their sources from this scarp-land.

Major Rock Types in Highlands  

1. The North central plateau, western highlands, Mandara mountain, Shebshi, Alantika, Obudu and Oban hills are made up of basement complex rocks (combination of igneous and metamorphic rocks)
2. Jos plateau is made up of volcanic rocks.
3. Udi hills are made up of carboniferous sedimentary rocks.

Importance of Highlands

1. It is a source of mineral like tin, gold, diamond which are useful to man
2. Mountains aid the formation of rainfall usually orographic or relief rainfall
3. Mountains are useful in times of inter-tribal war for easy defence against enemies
4. They are sources or the beginning of many rivers or streams
5. They serves as tourist centres
6. Highlands are noted for the erection of communication masts for proper reception
7. Highlands are noted for sources of some valuable building materials such as granite
8. Some mountains, as a result of their location do serve as wind breaks

DRAINAGE IN NIGERIA

Drainage refers to water bodies like rivers and lakes. Drainage of Nigeria can be discussed in two parts – rivers and lakes.

Rivers in Nigeria

Nigeria is drained by two main rivers – Rivers Niger and Benue.

Rivers Niger, the largest river in Nigeria has its source from Guinea highlands in Guinea. It passes through Mali and Niger Republic to Nigeria.

Rivers Benue has its source from eastern highlands and joins the Niger at Lokoja. Because of this, Lokoja is known as a confluence town.

Characteristics of Nigerian Rivers

1. The volume of the rivers changes with season
2. There is presence of rapids and cataracts which impede or disturb inland navigation
3. There is presence of debris like dead leaves, mud and woods
4. The colour changes with season
5. Rivers in the south flows in the north-south direction into the sea while rivers in the north flow in a radial pattern to different directions.
6. Most rivers in Nigeria are shallow and full of silt.
7. Most rivers are seasonal, as they flow during rainy season but stop or reduce flowing during the dry season.

Importance of Nigerian Rivers

1. Rivers especially large ones serves as a medium of transportation
2. Rivers are dammed for the generation of hydroelectric power supply
3. Water from rivers can be used for irrigation purposes for agricultural activities
4. Rivers are used for domestic purposes like cooking, washing etc.
5. Rivers provide employment for people like fishing, canoe or ship making
6. Rivers are known sources of food e.g. fish, prawns, crayfish and crab.
7. Some rivers are centres of tourist attraction and may generate foreign exchange for a nation
8. Some rivers are good sites for the construction of seaports and river ports.

River Basins     : River basin refers to the area generally drained by a river and its tributaries. In other words, they are naturally depressed low land areas. River basin is also called 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.

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

1. Man-made lake or artificial lake: These are lakes constructed by man. Examples are Lake Kainji on River Niger and Shiroro Lake on River Kaduna.
2. Natural Lake: These are lakes which exist naturally. Example is Lack Chad. Lake Chad is also described as an inland drainage because it receives water from many rivers such as Hadeija, Gana, Yobe, Yedseram etc.

Assignment:

1. State any two disadvantages of lowlands
2. State any three disadvantages of highlands
3. On a diagram map of Nigeria, show the major drainages in Nigeria