In 2005, a disaster struck New Orleans. You know the rest. Or do you?

The media reported that what happened in New Orleans was a natural disaster primarily affecting poor black people. On both counts, the media was wrong. But its inability or unwillingness to report the hard truth – that these tragic floods creating widespread damage were caused by manmade errors in engineering and judgment – has failed both journalism and public safety. For what happened in New Orleans could happen again in other cities across the United States.

In his feature-length documentary The Big Uneasy, humorist and New Orleans resident Harry Shearer gets the inside story of a disaster that could have been prevented from the people who were there. Shearer speaks to the tireless investigators and experts who poked through the muck as the water receded, and uncovers a courageous whistle-blower from the Army Corps of Engineers. His dogged pursuit of facts reveals that some of the same flawed methods responsible for levee failure during Hurricane Katrina are being used to rebuild the system expected to protect the “new” New Orleans from future peril.

In short segments hosted by actor John Goodman (Treme), Shearer speaks candidly with local residents about life in New Orleans. Together, they explore the questions that Americans outside of the Gulf region have been pondering in the years since Katrina: Why would people choose the live below sea level? Why is it important to rebuild New Orleans?

Shearer’s film is also laced with computer imagery that takes you inside the structures that failed so catastrophically, and boasts never-before-seen video of the moments when New Orleans began to flood and the painstaking investigations that followed. Likewise, the film demonstrates what awaits people on the inside who try to report painful truths to the powers that be.

The Big Uneasy marks the beginning of the end of ignorance about what happened to one of our nation’s most treasured cities—and serves as a stark reminder that the same agency that failed to protect New Orleans still employs the same flawed science in many other cities across America. Without improvements to engineering and accountability in oversight, the film cautions, we will be very sorry to see history repeat itself elsewhere. Nothing less than public safety is at stake.

Of course, why it took the bass player from “Spinal Tap” and the voice of Flanders, Smithers and Mr. Burns to reveal these tragedies is a story unto itself.