Floods in the United States: 2001–present floodgates of the Morganza Spillway were opened, marking the first use of the gates since the 1973 flood. 330 of the Bonnet Carré Spillway's gates were opened to save the levees protecting New Orleans. There was concern that if the Old River Control Structure, the Morganza Spillway, or the Bonnet Carré Spillway failed, the Mississippi River could change its course, flowing either into the Atchafalaya Basin or Lake Pontchartrain. In early September, the remnants of Tropical Storm Lee had stalled due to Hurricane Katia. As a result, the main cyclone stalled over the Midwest, and a cold front associated with
Flow control structure dam across a shallow stream, forcing all of the water to one side to allow it to be easily collected in a canal. This can keep a canal full even with very low flows in a stream. Another simple device is a series of concrete piers installed in a spillway to slow down the descending water so that it does not cause damage at the bottom of the spillway. Flow control structure A flow control structure is a device that alters the flow of water in a stream, drainage channel or pipe. As a group these are passive structures since