Answer the following questions briefly.

Why are the river plains thickly populated?

Generally, plains are very fertile. Construction of transport network is easy. Thus, the plains are thickly populated regions of the world.

Additional information: Plains are the most useful areas for human habitation. There is great concentration of people as most flat land is available for building houses, as well as for cultivation. In India too, the Indo-Gangetic plains are the most densely populated regions of the country.