How can Fargo North Dakota be flooded since it is basically on flat terrain?

Answer 1

In the spring, the Red River floods because all the snow melts and runs into the river. When the water goes over the banks, the houses and buildings that were built close to the river get flooded.

In addition:

It is because Fargo is on flat terrain that it is more susceptible to flooding. When the snow melts or the area receives a more than normal amount of rain, the river can not hold all of the water. Since the land is flat, the water overflows and fills all the flat areas.

Fargo has built dikes in many areas of town, which help control the flooding, but in 2009 there was so much snow fall in the whole Red River system that even the permanent dikes were not enough to handle all the water.