PLAQUEMINES PARISH, La. — First responders are battling rising water that is overtopping a back levee system that protects some parts of Plaquemines Parish from coastal flooding.

Plaquemines Parish Homeland Security Director Patrick Harvey tells WWL-TV that crews started seeing overtopping along the back levee system that protects the Myrtle Grove and Pointe Celeste areas off Highway 23 around 5 a.m. 

The levees that are seeing overtopping are separate from the flood defenses that protect the parish from the Mississippi River.

"Hopefully the overtopping does not cause a breach," Harvey said. "If so, we will continue to fight that battle, trying to protect Highway 23 if we need to evacuate any other residents from the southern part of the parish."

Highway 23 runs pretty much the length of the parish and if compromised, could cut off lower areas of the parish.

A mandatory evacuation order is in effect for the entire East Bank of Plaquemines Parish as well as the West Bank from the Oakville Flood Gate south to Venice, Louisiana.

When Highway 23 has flooded in years past, first responders would use the Mississippi River to evacuate people who did not leave. Harvey said that option is not possible this time because traffic on the Mississippi River levee could cause damage to the system holding back the swollen river. 

Plaquemines Parish, along with the rest of Louisiana's southeastern coast, is under a storm surge warning due to Hurricane Barry. The parish is expected to see between 3 to 5 feet of storm surge from thehurricane.

LIVE UPDATES:Hurricane Barry inches to landfall on Louisiana coast

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Stay with Eyewitness News on WWL-TV and WWLTV.com for more on this developing story.