If Americans have forgotten about New Orleans, the documentary "Trouble the Water" - which won the Grand Jury Prize at this year's Sundance Film Festival - is a vital and harrowing reminder.

The story landed in the laps of Tia Lessin and Carl Deal. The movie's first scenes show the filmmakers shooting at a Red Cross shelter when they are approached by Kimberly and Scott Roberts, a young couple who lived through Hurricane Katrina in New Orleans' Lower Ninth Ward. "I got the footage nobody else has got," Kimberly tells the filmmakers.

Indeed she has. She had her camcorder running during Hurricane Katrina's landfall, as the rain and wind beat down. She kept shooting from her attic, where her family had to go when the Industrial Canal levee three blocks away crumbled. The footage, jumpy and erratic as a home movie, is terrifying.

After the horror comes the dread, as Kimberly and Scott return to their old neighborhood to see what they can salvage. They deal with the bureaucracy of FEMA (which hasn't sent Kimberly the money it promised) and the Louisiana prison system (Kimberly's brother was in the Orleans Parish lockup when the hurricane hit). They also weigh a tough decision: start a new life in Memphis, or go back to reclaim their battered hometown.

Lessin and Deal are protégés of Michael Moore, but their style is less confrontational. They know they just need to show the Roberts family's situation, and the audience will get angry without having to be prompted.

But if we're angry, we are also heartened by this couple's positive attitude. Kimberly is an aspiring rapper - and the movie stops to allow her to express her pain and her optimism through one of her songs. It's a moment that crystalizes the indomitable spirit of the Roberts family, and of New Orleans herself.

Sean P. Means can be reached at movies@sltrib.com or 801-257-8602.