The Bonnet Carré Spillway is a flood control operation in the Lower Mississippi Valley. Located in St. Charles Parish, Louisiana – about 12 miles west of New Orleans – it allows floodwaters from the Mississippi River to flow into Lake Pontchartrain and thence into the Gulf of Mexico. The spillway was constructed between 1929 and 1931 following the Great Mississippi Flood of 1927 and has been designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.