I think the belief comes about because forests do help to reduce floods in small areas, and so people assume it must also apply to severe floods in large areas. |
Most people automatically believe that if there's a large flood then loggers and deforestation are responsible. In most cases it's not true. |
The simple explanation for large-scale flooding is that it rains a huge amount and that flooding is part of natural processes. There is a tendency to look for culprits when these natural events occur. |