Which factor could cause the fall of a civilization?

One factor that could help cause the fall of a civilization is: poorly managed irrigation

Poorly managed irrigation system will cause a lot of harvest failure that could lead to massive food shortages.
When this basic necessity is not met, people tend to be more violent and will start to revolt against the government.

Cherokee  removal, part of the trail of tears, refers to the  forced  relocation between 1836 and 1839 of thecherokee  nation from  their lands ingeorgia, south carolina, north carolina, tennessee, texas, and alabama to the indian territory (present day oklahoma)  in  the thenwestern united states, and the resultant deaths