Three and a half years is a long time to grapple with the kind of anguish that weighs on writer John Biguenet, and he admits to loathing every step of the process. But he can’t bring himself to let it go. He says his work is not finished.

With the May staging of his latest play, the Robert Hunter Distinguished Professor at Loyola University may be two-thirds of the way through articulating what the flood of 2005 did to his city.

The drama, called “Shotgun,” is the second in a three-play cycle that Biguenet undertook during the months following New Orleans’ disastrous tangle with Hurricane Katrina. The cycle began with his “Rising Water,” staged at Southern Rep Theatre in 2007. He says the project arose from a need to tell the story of how the city suffered as a result of negligence and bungling by people charged with protecting it.

Before Katrina, the O. Henry Award-winning author had begun working on a new play to follow on Southern Rep’s successful staging of his first dramatic script, an adaptation of his short story, “The Vulgar Soul.” But in the weeks following the hurricane and subsequent failure of local floodwalls, Biguenet — whose Lakeview home was among the flood’s casualties — began chronicling for The New York Times the wrenching losses and heartbreaks he saw all around him. “I was just so outraged and furious,” he says. His feelings eventually led him toward a new play.

“Four months into the flood I began to write about, in a fictional way, what I had been writing about for the Times,” he says. He told Southern Rep’s then-Artistic Director Ryan Rilette that he had an idea for a play about a couple trapped in their attic as the flood waters rose.

“Stop everything else and write it,” Rilette told him.

With help from a commission award from the nonprofit alliance National New Play Network, Biguenet worked on the play through 2006. Early the next year, the story of a married couple forced by a flash flood to face their destiny and themselves on the rooftop of their home, unfolded on Southern Rep’s stage and became the best-selling play in the theater’s history.

Biguenet already was laying plans for where he would go with the second installment of his “Rising Water” cycle. It was about that time that actor Lance Nichols, who had appeared in another post-Katrina play called “The Breach,” met Biguenet and suggested: “Why don’t you write something for me?”

In a surprising response, Biguenet said he’d give the idea some thought.

“I really forgot about it after that,” Nichols recalls. “Then last fall Southern Rep Artistic Director Aimée Hayes called and said, ‘We’re going to do this play that John Biguenet wrote for you.’ ”

In “Shotgun,” Nichols plays the role of Dexter, a black man displaced by the flood and forced to move in with his daughter, whose shotgun house remained dry. The daughter rents the other half of her double house to a white man and his teenage son who also lost their home in the flood.

“I had Lance in mind from the beginning,” Biguenet says.

He knew, also, that he would again use local architecture as a dramatic element and a means of containing the interactions of characters in conflict. In “Rising Water” the setting was an attic and rooftop. In “Shotgun,” the constraining structure is the distinctively local house.

“The architecture gives that sense of people living under same roof but with a wall running between them,” Biguenet says. “They try to live together under one roof, but it’s at the very moment when (New Orleans Mayor Ray) Nagin makes his ‘chocolate city’ speech. I think from then until today the sense of racial tension here is greater than at any time in my life.”

Like other local actors who have been cast in post-Katrina dramas, Nichols says his own experiences help enrich his role. “Being born here and having been displaced by Katrina for over a year, I can relate to Dexter’s feeling of not having a place to go back to.”

He says the play also reaches beyond black-and-white issues to human fears of losing power over one’s situation. “When you have been in a certain type of environment all your life and suddenly that is no longer available to you, there’s a sense of not being in control.”

Nichols is pleased to have a chance to work with a director he knows from a previous production. Valerie Curtis-Newton, artistic director at Seattle’s Hansberry Project and head of the directing program at the University of Washington, is directing “Shotgun.”

As the cast went into rehearsals for the production, Biguenet was at work on part three of his Katrina cycle, tentatively entitled “Mold,” along with a novel about the flood and post-Katrina New Orleans. The projects force him to relive on a daily basis the torturous details of the 2005 flood and the  tangle of emotions that have characterized life in the city ever since. He says he looks forward to putting it all behind him, but a tall stack of 2005 and 2006 newspapers that he keeps next to his office desk is a reminder that he has more to do.

“I didn’t want to write any plays, and I hated every minute of this,” he says. “I still hate it. And now I’m writing a novel about it and I hate that too. It’s so awful to live with the details of this stuff and keep those newspapers. But there are so many horrifying stories I didn’t include in the play that I will include in the novel.”

Biguenet believes it’s a writer’s responsibility to raise questions that help the broader community focus attention on important issues.

“Just as I had to try to give an accurate picture of what happened on August 29, 2005, I’ve got to bring the news to the rest of the country that this thing isn’t over for us,” he says. •

“Shotgun” by John Biguenet, directed by Valerie Curtis-Newton, starring Rus Blackwell, Kenneth Brown Jr., Donna Duplantier, Alex Lemonier and Lance E. Nichols. May 6-31, Southern Rep Theatre, 333 Canal Place (third floor), New Orleans; Box office: 504.522.6545,