The Army Corps of Engineers on Saturday closed the Inner Harbor Navigation Canal-Lake Borgne Surge Barrier Gulf Intracoastal Waterway sector gate and Bayou Bienvenue lift gate ahead of the arrival of a weakened Tropical Storm Karen.

The closure happened about 9:20 a.m.

The sector gate, which is closed in advance of a tropical weather event that could make landfall in southeast Louisiana, is designed to reduce the risk associated with storm surge that could affect areas hardest hit by Hurricane Katrina, including New Orleans East, Gentilly, the 9th Ward and St. Bernard Parish.

The 1.8-mile-long barrier works with the Seabrook Floodgate Complex. That structure will be closed later Saturday, corps officials said.

The Seabrook barrier prevents storm surge from entering the Industrial Canal.

The National Hurricane Center said that Karen, which weakened overnight, is expected to move over southeast Louisiana Saturday night and early Sunday.

The storm’s maximum sustained winds were about 40 mph, down from about 45 mph on Friday night.

Karen was about 180 miles away from the mouth of the Mississippi River on Saturday morning and moving north at 7 mph. A turn toward the northeast is expected Saturday night.

A tropical storm warning is in effect for Morgan City to the mouth of the Pearl River while a tropical storm watch is in effect for metropolitan New Orleans, Lake Maurepas, Lake Pontchartrain and areas east of the mouth of the Pearl River to Indian Pass, Fla.

A tropical storm warning means tropical storm conditions are expected somewhere within the warning area. A tropical storm watch means tropical storm conditions are possible within the watch area.

Karen is expected to make landfall on Sunday night near the coast of Missippi and Alabama and weaken to a tropical depression.

Staff photographer John McCusker contributed to this report.