How does flood water stay in one area because last time i checked nothing was holding the water in, and if the earth is round it should just spread out shouldn't it?

Reason why flood water stagnant in same area:

A flood occurs when there is a excessive rain, breakage of dam, heavy climate change and speedy melting of snow or ice. Usually the flood water can be  constrained in a particular place that can be in a crater surface. This is caused by improper drought management and and natural hazards.

Though the infrastructure development keep on improving, the drought management system remains the same. So, the flood water stays in one area even though the earth is round. The government should take steps to ensure the security of citizens by taking care of the flood water development.

It can be spread out or saved by rain water management system. If the flood water stays in one area that is dangerous and make you ill-protected to  infectious diseases, chemical hazards, and injuries.

question

which are human systems?

the amazon rain forest

the appalachian trail

the george washington bridge

the himalayas

the hoover dam

the north american free trade agreement