NCERT Solutions for Class 7th Social Science Chapter 3 b) Floods — LET'S EXPLORE
Book page 60 Updated on2026-09-19
Q1.
Have you seen or read about floods? Look at the physical map of India. Discuss in pairs why you think floods occur in the areas mentioned above.The physical map of India given at the end of the book — redrawn here with its legend and its latitude and longitude lines.
Answer
The states the chapter names are Uttar Pradesh, Bihar, Kerala, Andhra Pradesh and Assam. Put a physical map beside that list and the reason jumps out: every one of them is either a great river plain or a heavy-rainfall coast — or both.
State
What the physical map shows
Why it floods
Assam
The Brahmaputra valley, shut in by hills, fed by Himalayan snow-melt; very heavy monsoon rain in the North-East
An enormous volume of water in a narrow, almost flat valley with nowhere to spread; the river also carries huge amounts of silt, which raises its bed
Bihar
The northern Ganga plain, crossed by the Kosi, Gandak and Ghaghara coming down from Nepal
Rivers drop from steep mountains on to a flat plain, lose speed, deposit silt and spill over. The Kosi is called ‘the sorrow of Bihar’ for shifting its course
Uttar Pradesh
The Ganga–Yamuna plain, extremely flat, very densely settled
A slope so gentle that water drains away slowly; heavy monsoon rain upstream arrives all at once
Kerala
A narrow coastal strip with the Western Ghats immediately behind it; tropical wet climate
The Ghats squeeze very heavy rain out of the southwest monsoon, and the short, steep rivers reach the sea in hours, not days
Andhra Pradesh
The Krishna and Godavari deltas on the east coast
Low, flat delta land plus the cyclones that regularly strike the eastern coast, bringing torrential rain and sea surge together
Two more kinds of flood the chapter adds:
Glacial-lake floods in the Himalayan regions. Glacial lakes are held back by a barrier of rock and ice. If the glaciers melt too fast — as is increasingly the case — or if there is too much rain, the build-up of pressure can make the water break through. This is a glacial burst, and it often has devastating consequences.
Urban flooding. Many cities flood in heavy rain because of an overburdened drainage system, poorly planned construction encroaching on the waterways, and concrete or asphalt surfaces that do not allow water to be absorbed by the earth.
Why the answer is a combination, never one cause: a flood needs both too much water and nowhere for it to go. Heavy rain over hard rock in a steep, empty valley makes a torrent, not a disaster. The same rain over a flat, silt-choked, densely populated plain makes a flood — which is why the physical map, not the rainfall map alone, tells you where floods will happen.