M: If we don't operate and we exceed the maximum capacity of the system along the Mississippi River, levies will be overtopped.
SIMON: NPR's Greg Allen is in Baton Rouge and joins us now. Greg, thanks for being with us.
GREG ALLEN: Sure, Scott.
SIMON: To those of us who haven't been through this, this seems like a pretty drastic move to open a floodway that could displace 25,000 people. But there's no alternative?
ALLEN: That would potentially affect hundreds of thousands of residents. It would also disrupt shipping and other business in New Orleans, and that could cost millions of dollars a day to the region's economy.
SIMON: So help us understand what's going to happen when those floodways are opened later today. Flooding starts immediately?
ALLEN: Also after three days or so, water will begin to back up in the basin, and it's that back flooding that most residents are concerned about. To help prevent that back flooding, the local levy board has sunk four barges at a key point in one of the bayous and hope that will minimize flooding in many of these communities.
SIMON: Now, earlier in May the Army Corps of Engineers encountered a lot of opposition and even some lawsuits when they planned to try and open a similar floodway in Missouri. Any opposition in Louisiana?
ALLEN: Yesterday I talked to a lady named Sheryl Vaughan in Pierre Part. She was out filling sandbags with their son, working to build a four foot tall levy around her house. I asked her why people aren't angry about the decision to open the floodway, and this is what she had to say.
SHERYL VAUGHAN: We were all raised on the water. My dad made his living fishing. My son has fished. My son-in-law makes money fishing, so it's kind of like, you know, something you just have to do. I don't want to live in the city. I want to live here, but I just don't wanna have to fight the water.
SIMON: Greg, are people starting to evacuate?
ALLEN: But of course it's early days. The Corps said the floodwaters are not expected to crest here for another week at least, and after that it could be two to three weeks before flood waters recede.
SIMON: NPR's Greg Allen in Baton Rouge. Thanks very much.
ALLEN: My pleasure. Transcript provided by NPR, Copyright NPR.