If you join us for a plantation or swamp tour you’ll get a chance to cross the Bonnet Carré Spillway, one of the most important engineering structures that helps control the normal flooding of the Mississippi River that occurs in the spring. The Spillway, which runs along Interstate 10 to the West of the city, can be opened to restrict the flow of the river toward its main channel which has the effect of causing the water level to rise just enough to spill into the diversion channel. When the waters are especially high the Spillway can also divert water into Lake Ponchartrain, which in turn dissipates excess volume into the Gulf of Mexico. The Spillway helps to protect New Orleans from springtime floods by diminishing the flow of the river before it runs into the city’s levee system, thereby reducing the stress on the levees. The Spillway was originally built in response to the Great Mississippi Flood of 1927 that caused devastating damage throughout the Mississippi River basin. Since the first opening of the Spillway during the flood of 1937 the Spillway has been opened ten times, most recently in May of 2011 when heavy spring rains and snow melts to the North caused river levels to rise to the flood stage of 17 feet.