River levels highest in years; spillway to open

Published 12:00 am Saturday, April 30, 2011



LAPLACE – High water levels along the Mississippi River has prompted Army Corps of Engineers officials to consider opening the Bonnet Carre Spillway in Norco to relieve pressure on levees further downriver.

At a press conference Thursday afternoon, Gov. Bobby Jindal announced the flood control structure will likely open sometime between May 7 and May 13. Jindal also declared a state of emergency because of river levels that are predicted to crest at their highest point in about 12 years.

The unusually high river has been triggered mostly by heavy rains in the Midwest, including more than 11 inches in Cincinnati and almost 7 inches in St. Louis during the past three weeks, according to hydrologists with the National Weather Service’s Lower Mississippi River Forecast Office. Also contributing to the high water is a week’s worth of storms in parts of Oklahoma, Arkansas, Missouri, Indiana, Illinois, Kentucky, Mississippi, Alabama and Tennessee that have spawned nearly 15 inches of rain and several tornadoes. Flood gages throughout the region are expected to show major and minor flood stages in the next few days.

Mike Stack, chief of emergency management for the corps’ New Orleans District office, said levee surveillance from New Orleans to Baton Rouge has increased, and indicators show the river could rise to as much as 17 feet in some locations. He said the river is expected to stay at that level for several days. Although the official flood stage in the region is 17 feet, levees protect the area to 20 feet.

Water has already begun seeping through the spaces between the wooden pins that make up the spillway structure. Stack said that is a regular occurrence when the river goes above 12 1/2 feet. He said inspections of levees are conducted daily by levee district employees once the water goes above 15 feet.

Stack said the decision to open the spillway is based on a combination of factors, including whether the amount of water flowing south of the spillway is expected to climb above 1.25 million cubic feet per second and how long the upper portions of the levees have been saturated with water. He said it takes about 10 days to prepare for the opening.

The spillway was last opened in April 2008 after high levels of snowmelt across the Midwest brought river levels near flood stages. The corps opened 84 of the spillway’s 250 bays to relieve the pressure. Stack said it has not been determined how many bays will be opened this time or how long it will stay open.

The high river level is also expected to bring about the enforcement of a variety of restrictions on construction activities near the river levees, including prohibiting pile driving and excavations near the lower parts of levees without special permission for the corps and levee district.