I do not agree with the statement.
The cause of river flooding can indeed be a result of human factor,for instance when the river channel is narrowed by human, or there are too much depositions into the river causing an increase in discharge, that the river soon failed to handle and cause flooding.
However, physical factor are more likely to be the causes. Raining is a very typical physical factor that cause flooding,as it directly increase the discharge of the river, triggering the chances of overflowing leading to flooding.
There are also natural deposition. After raining,soil will be deposited into the river causing it's capacity to be smaller, increasing the discharge and are more prone to flooding.
Hope it helps!
