How did convicts (prisoners) play a
role in the Flood of 1927?

They were used as labor to built levees and floodways to prevent future flood.

Explanation:

The states often used prisoners as labors for both government project or they can put them on hire as labors for private companies. This method will resulted in lower cost since they do not necessarily have to pay the convicts for their work.

Flood of 1927 was regarded as the most destructive flood in american history. The flood caused suffering for around 630,000 citizens.  In order to prevent this from happening again, the federal government initiated one of the largest infrastructure building project in American history. They initiated the project to  built levees and flood ways along the Mississippi river.

Convicts made up the vast majority of workers that were used in that government project.