After a great downpour, an otherwise dry land is covered by standing water, which stays for a period of time. This is an example of flood. Flooding is caused by different situations.

In an area where the soil is sandy, rainwater sinks into the ground readily.  This is however  not the case if the soil is clayey.  This is because clay retains water. As a result, the rain water does not sink readily. In areas where the soil is classy therefore, flooding is possible after a short rainfall.

In coastal areas like Port Harcourt, Lagos and other places where the land and sea meet, the level of water in the sea rises and falls. This rise and fall of the sea is referred to as the tide of the sea.  Depending on the time if year and the season,tides can be low, high or very high. Tides are caused by the pull of the moon and the Sun. The flood caused by seawater is more severe during the rainy season when the water level rises and spreads across the land.  There is also an overflow of water from the sea into nearby rivers.  Excess water from the rivers also cause flooding of the land nearby.

Rivers may overflow their banks during the rainy season. If the rain is very heavy, the river may overflow it’s banks to the neighbouring land, making the land flooded.  Thus occurs more often with large rivers like the River Niger and River Benue.

There are many ways to prevent flood. Construction of dams along rivers that overflow into neighbouring land can help in preventing flooding. This is because part if the water that us carried by the river us stored in the dam.  The speed and the volume of water carried by the river are thereby reduced. This greatly reduces the tendency to flood.  This is the case with river Niger in Nigeria,  Mississippi and Missouri river in the United States. Flooding can be prevented through the construction of river or sea embankments. An embankment is an artificial bank usually made with stones to hold back water.  Gutters can also be cleared to allow for the free flow of rain water. 

In urban areas, surface drainage paths should be designed and constricted by competent engineers. The floor of the gutter is made of concrete and designed to have a slope that allows water to flow away easily. The sides are made of concrete and therefore hold back water.  The top of the drainage path may be covered with concrete slab to prevent cars and bicycles running into it or children falling inside it. Another reason is that some people may throw rubbish into the drainage to block it, thereby causing a flood.

(Adapted from Basic Science  – An Integrated Science Course for JSS 3 by F. O. C. Ndu and E. O. Somoye.)


The following sentences are the summary of each of the paragraphs in the passage, ‘Floods’.

They are not arranged in the correct order. Rearrange them properly after reading the passage again and state which is the summary of each paragraph in the passage. Write each summary besides its paragraph number.

* Well constructed drainage can be used to construct drainage in urban areas.

* Floods can happen when water overflows riverbanks.

* Floods occur after a heavy rainfall.

* A clayey soil easily allows floods to happen.

* Water level rise caused by tides, also causes floods.

* Construction of dams and embankments can prevent floods.