The electromechanical sirens that authorities in Venice activate to warn residents of flood emit threatening wails reminiscent of air attack warnings and do not convey the gravity of the threat, and do not reach isolated or distant areas. For these reasons, a study was initiated to address the possibility of replacing the sirens with a loudspeaker stystem that would provide more uniform coverage as well as information about the tide level. First, the current alert system was analyzed using off-the-shelf acoustic simulation software and a specially designed visualization tool. Second, a form of constraint logic programming was used to determine the optimal placement of loudspeahers in Venice. Third, the alert sounds were created for the demanding listening environment. Finally, the alert signals were iteratively validated and redesigned using human testing.