Heavy summer rains are coming to a small town along the Mississippi River, but the mayor (Joseph O’Brien) is in denial. “Aw, c’mon,” he tells a concerned farmer (Jonathan Rayson) who would like to see the levee shored up. “The river’s never come anywhere near the top.”

Famous last words. Since Peter Mills and Cara Reichel’s musical is titled “The Flood,” there’s little doubt that the fictional burg of Meyerville, Ill., is in for a dousing, if not a Hurricane Katrina-style apocalypse.

Inspired by the devastating Midwest floods of 1993 and in the works since 2000, “The Flood” can’t be blamed for being upstaged by last year’s Gulf Coast deluge. What this eager, accomplished show can be rapped for, though, is that it manages to get nearly everything right, except the most crucial bit: its substance.

Directed with sweep and flow by Ms. Reichel, and performed by an able, ingratiating cast of 23, “The Flood” plays like a demonstration-model American musical. As soundly constructed as Kanae Heike’s woodsy, modular set, the show has an alternately soothing and majestic score that evokes the free-ranging Americana of Stephen Flaherty and Lynn Ahrens (“Ragtime”).

But this can’t make us care a whit about the show’s cookie-cutter characters: the aforementioned farmer and his indecisive schoolteacher fiancée (Catherine Porter); the glad-handing mayor and his hothead teenage son (Matt DeAngelis); or the son’s sweet, bland girlfriend (Jamie Davis).

Her family is marginally more interesting: Her dad, helpfully named Ezekiel (Drew Poling), has long prophesied the river’s rise to deaf ears, and her mildly retarded sister (Jennifer Blood) is ominously overfond of the water, personified by a rag-covered, melisma-purring A’lisa D. Miles.

Is the besieged Meyerville the show’s true lead character? Anatevka it’s not; this white-bread outpost makes Mayberry look positively outré. Bet the church choir sounds great, though.