To Resist Flooding, |Spillway Opens Early

     
NEW ORLEANS (CN) – Hundreds gathered Sunday to watch as the Bonnet Carre Spillway, located 26 miles west of New Orleans, was opened to take pressure off the swollen Mississippi River.
     Cranes atop the weir that separates the Mississippi River from the Bonnet Carre Spillway in Norco began pulling long timber “needles” out of the first of 350 bays Sunday morning as part of a plan by the U.S. Army Corps of Engineers to reduce the river’s flow as it moves past New Orleans.
     By opening the spillway, the Corps is redirecting some of the water to Lake Pontchartrain.
     During a 10 a.m. news conference before the opening Sunday Mayor Mitch Landrieu praised the role of the spillway in keeping New Orleans and the surrounding areas dry.
     “What we’re witnessing right now is really an engineering miracle,” Landrieu said.
     But the tone of U.S. Rep. Garrett Graves, R-Baton Rouge, during the press conference was more cautious. Noting this as the earliest opening of the spillway since its 1931 completion, Graves said the reasons behind the opening need to be studied.
     “Right now we’re seeing a pretty amazing event,” Graves said. “The Bonnet Carre Spillway has traditionally been opened about once every 10 years. “
     “Yet, as many of you know,” Graves continued, “we opened it in 2011, and we also opened it in 2008. Clearly the trends we’re seeing are changing right now. We’ve got to watch this very closely and better understand what’s happening with the Mississippi River system to make sure we don’t flood communities down here.”
     Graves pointed to ocean vessels meandering past the spillway weir in the river, seemingly at the same height as the top of the levee. He noted that the spillway and levees provide protection for water-based business for 31 states along the Mississippi River watershed. But the watershed drains 41 percent of the continental United States, Graves said.
     Several hundred people showed up for the opening of the spillway Sunday, many of whom came by foot atop the Mississippi River Levee to witness the first timber being pulled from the weir before the brown water of the Mississippi plunged into the spillway.
     The needles are grouped into 350 linear bays of 20 needles each and the Corps will remove as many as needed to divert floodwaters. In 2008, fewer than half of the Bonnet Carre’s bays were used. But when the structure was most recently used, in May 2011, more than 94 percent of bays were opened.
     The Corps removed 400 of the needles Sunday, which opened 20 of the structure’s 350 bays. An additional 30 bays could open Monday, depending on the river’s speed and levels. The objective is to keep the river below the 1.25 million cubic feet level that initiated the opening of the spillway. At that flow rate, the river would fill the Louisiana Superdome in New Orleans in 1 second.
     On Sunday, the river was at 16.2 feet in New Orleans and is expected to reach 17 feet 17 feet being the height of the levee walls that protect New Orleans from flood on Tuesday, even with the opening of the spillway.
     According to estimates from the National Weather Service’s Lower Mississippi River Forecast Center, based in Slidell, the river will remain at 17 feet in New Orleans through Feb. 3.
     As the gates opened, scientists in airboats were monitoring the environmental effects and the debris entering the spillway. Workers for the Corps and others will continue to monitor river levels before deciding whether to relieve more pressure from the Mississippi River by opening the Morganza Spillway, which is located upriver from Baton Rouge and flows into the Atchafalaya River Basin.
     Because parts of that basin will flood even if the Morganza isn’t opened, people have begun taking valuables and other possessions from camps and other property near Morganza and have begun protecting what is left with sandbags. Power companies serving properties in the area said they are disconnecting electric meters.
     The governor’s Office of Homeland Security and Emergency Preparedness reported Friday that it had 842,000 sandbags in stock and had already issued 26,000 sandbags to Avoyelles Parish, 13,000 to West Feliciana Parish and 13,000 to the Louisiana State Penitentiary at Angola, which is bounded by the Mississippi River on three sides.
     Since Gov. Bobby Jindal’s Dec. 30 State of Emergency declaration, a number of state agencies issued emergency plans due to “an imminent threat of flooding.” On Thursday, the Department of Natural Resources declared an emergency for the state’s oilfields and structures and ordered operators to secure facilities and remove chemicals from sites and pipelines.
     Sunday’s opening of the Bonnet Carre Spillway marks its 11th since its completion in 1931. The spillway was designed following the Great Flood of 1927.
     The Morganza has been used more infrequently. Opening this year would be its third since it was completed in 1954.
     Usually, river levels rise in the spring after the snow melts in the Midwest. Typically, the Bonnet Carre has opened in March or later. But the first opening, in 1937, was also early, on Jan. 28. And in 1950, the spillway opened on Feb. 10.
     Heavy rainfall in the Midwest last month caused the Mississippi and its tributaries to overflow, triggering severe flooding upriver in Illinois and Missouri, and swelling the river to the height of the levee system in New Orleans.

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