Atchafalaya Basin from the Mississippi, Red and Black rivers is diverted into the Atchafalaya at the Old River Control Structure. This flow diverts on average 25 percent of the Mississippi River flow down the Atchafalaya. In times of extreme flooding, the US Army Corps of Engineers may open the Morganza Spillway and other spillways to relieve pressure on levees and control structures along the Mississippi. On May 13, 2011, in the face of a rising Mississippi River that threatened to flood New Orleans and other heavily populated parts of Louisiana, the USACE ordered the Morganza Spillway opened for the first time since
Pequannoc Spillway which lies on the Pompton River. The Pequannoc Spillway is an early 20th-century concrete spillway over 270 feet wide, equal in girth to the Great Falls of Paterson located along the Pompton River a quarter-mile south of the Pompton dam and associated guard bank in Pequannock Township's Aquatic Park. The dam is a run-of-the-river spillway, which traverses the width of the river and at normal water elevation allows water to spill over its face. The structure is 22 feet tall, though possesses only an 8-inch over 3 foot grade on the upstream side. An associated guard house sits near the