In 2011 Snow Melt and Heavy Rains in the Upper

In 2011 snow melt and heavy rains in the upper Missouri River drainage basin produced record runoff that led to extensive flooding in lower Missouri River valley, despite the construction of numerous large flood control dams built on the river in the mid 20^th century. What type of failure in an artificial flood control system is this an example of?

A) a flood outside the design capabilities of the dam system overwhelmed the capacity of the reservoirs forcing opening of flood gates, exacerbating the downstream impact of the flooding
B) insufficient levee construction downstream of the dams
C) bad planning by the water managers who cared more about power production than downstream flooding
D) It was not a failure; the dam system worked as planned. It was poor planning by the downstream government agencies.