In environmental geography, which of the following human activities is a major cause of frequent and severe floods in rivers?

Introduction / Context:
Floods in rivers are a common topic in environmental geography and disaster management. Students are often asked to distinguish between natural triggers of floods, such as heavy rainfall or snowmelt, and human induced causes that make floods more frequent and severe. This question tests your understanding of how changes in land use, especially in river basins and catchment areas, can alter runoff, infiltration, and river discharge, thereby increasing flood risk.

Given Data / Assumptions:

The focus is on frequent and severe floods in river systems rather than rare or exceptional events.
We are comparing different possible causes such as dams, snowfall, earthquakes, and deforestation.
Natural rainfall is assumed to occur, but the question emphasises human activities that worsen flooding.
The river basin and catchment area include forests, slopes, and soils that influence runoff and storage of water.

Concept / Approach:
The key concept here is the hydrological cycle and how land cover influences the balance between infiltration, surface runoff, and groundwater recharge. Forested areas act like sponges. Tree roots bind the soil, the leaf litter increases infiltration capacity, and the canopy slows down raindrops. When forests are removed at a large scale, the catchment loses this sponge effect. Rainwater runs off quickly, reaching rivers in a short time and causing a sharp increase in discharge, which can lead to a flood peak. Therefore, understanding the role of deforestation in altering hydrological response is central to answering this question correctly.

Step-by-Step Solution:

Verification / Alternative check:
An alternative way to check is to recall case studies from geography or environmental science textbooks. Many river basins where forests have been cleared for agriculture, urbanisation, or logging experience greater flood frequency and severity. Textbooks often cite examples from Himalayan foothills, tropical river basins, and other regions where catchment deforestation increased peak flows after storms. This real world evidence supports the idea that deforestation is a major contributing factor to river floods.

Why Other Options Are Wrong:

Common Pitfalls:
A common mistake is to assume that any dramatic natural event such as an earthquake or heavy snowfall must be the principal cause of floods. Another pitfall is to think that dams always create problems, without distinguishing between their intended role in flood control and accidental failures. Students should carefully read the phrase major cause and notice that it points to a recurring, widespread factor like deforestation rather than rare events. It is also important to recognise that human land use changes often have a stronger cumulative effect on flooding than single natural events.

Final Answer:
The correct answer is Extensive deforestation in the river basin and catchment area, because removal of forest cover increases surface runoff and leads to more frequent and severe river floods.