Harry Schearer is mad as hell, and he's not going to take it anymore.

Harry Shearer, in an image from 'The Big Uneasy.' And so, after five years of cringing whenever Hurricane Katrina is referred to as "a natural disaster," the multihyphenated entertainer (actor-humorist-commentator-musician-broadcaster-pretend rock star) and part-time New Orleanian is adding another hyphen to his job description: documentarian.

The result? "The Big Uneasy, " landing tonight (Aug. 30) in 200-plus theaters nationwide. It's an unconventional release, to say the least -- opening on a Monday and, in most cases, playing for one night only -- but one timed to coincide with the storm's fifth anniversary.

The gist: Eh, you might want to keep that ax in your attic.

"As the authors of the Berkeley report say, this was not a natural disaster, " Shearer said, calling to discuss the movie recently after a screening in Washington. "This was a man-made disaster, and therefore it could have been prevented -- and therefore its repetition can be prevented. But it won't just happen by wishing."

What will help, Shearer hopes, is holding the Army Corps of Engineers' feet to the fire, and making sure it doesn't repeat the mistakes that experts say caused the flood in the first place.

That's what where "The Big Uneasy" comes in.

Shearer asked notable New Orleans celebrities, including Brad Pitt and Jennifer Coolidge, to help provide voiceover for his film, and John Goodman to host whimsical "Ask a New Orleanian" interstitials. But the real stars are two investigator-pariahs whose post-storm inquiries cast doubt on the Corps' ability to protect New Orleans.

Those two men -- former Louisiana State University Hurricane Center deputy director Ivor Van Heerden and University of California, Berkeley engineering professor Bob Bea -- conducted in-depth investigations into what caused the 2005 levee breaches. Their results laid the blame squarely at the feet of the corps, which "The Big Uneasy" suggests still operates in the same dysfunctional manner as before the storm.

Their unwillingness to back off their findings upset the powers-that-be, taking a toll on their careers. (Van Heerden, for example, first was asked not to speak to the press and later was dismissed from LSU.) Shearer does his best to let Van Heerden and Bea have their say in "The Big Uneasy, " giving them an opportunity to walk viewers through their findings. It is dense stuff at times, given the science at work, but, for the most part, it's surprisingly accessible. Shearer said that's not by accident.

"In one way, I was kind of a good person to tell this story, because I don't know crap about engineering, " he said. "So if I can make it understandable to myself, I hope that I can turn around and then make it understandable to other people who don't know crap about engineering. Thank goodness both Bob Bea and Ivor van Heerden are, among other things, great teachers and can make it clear that this isn't rocket science. This is basic, kind of -- there's a lot of common sense in engineering.

"But I did try to do things to make it not an instructional film. ... I tried to make a film that can be compelling while really doing justice to the story."

It being a Harry Shearer project, "The Big Uneasy" naturally boasts a sprinkling of humor, although not the kind that fans of his work on "The Simpsons" and "This Is Spinal Tap" might expect.

"There's very little of me, but there's humor, " he said. "The laughs -- there are laughs in the film -- they come, I think, from people who aren't intending to be funny. Without tipping it one way or the other, they're there for their value as responses to other things that are said in the film -- because I'm being a responsible person and giving people a chance to answer accusations. And the answers sometimes are laugh-provoking."

Ironically, the screening that brought Shearer to Washington was at the Newseum, that celebration of all things journalism. After all, he said, the only reason he made "The Big Uneasy" in the first place is because the national news media have done such a poor job of telling the real story. "I think rather than me explain it, I'll let a prominent national anchor explain it in that person's own words: When I asked why, at a certain point well along in time, the viewers of that particular newscast still didn't know why New Orleans flooded, that anchor's answer was, 'We just feel the emotional stories are more compelling for our audience.' "

Because the exchange wasn't recorded, Shearer is reluctant to provide that anchor's name, although he says it's telling of how the news media have become far more Kent Brockman than Edward R. Murrow.

Deciding that a documentary was the best way to tell that untold story (but realizing that nobody else was going to do it), Shearer decided in January to make "The Big Uneasy." Documentary filmmaking is a new discipline for him (not counting the faux documentary "This Is Spinal Tap"), but he's never been one to shy from work.

"For better or for worse, " Shearer said, "I was kind of devoted to being the un-Michael Moore and having a much more traditional idea of a documentary in mind, which is, a large story, too large to be told in a three-minute news piece, but that needs to be told, and told through the eyes and the words of people who actually know what they're talking about."

And if it all makes you feel a little uneasy? Well -- good night, and good luck -- Shearer has done his job.

"The Corps of Engineers makes very reassuring statements about the size and the expense of the work that they're doing right now, " he said. "And if you look at that at face value, it's meant to reassure us, meant to make us feel, 'Hey, we're OK. We're protected. Everything's fine.' And people with short memories might feel good about it. But people with long memories will recall those were the same kinds of statements the corps was making about the old system before 2005. We believed them then, and we were reassured by them then -- and look what it got us."