A DREDGE BROKE free of its anchor in a gale and crashed into the only bridge to Hatteras Island, N.C., Friday, and the span collapsed an hour later. Thousands of residents had no way on or off the island except ferries . . . USING THE BLOODY bandages from his twice-slashed wrist as a noose, a man on trial for attempting to kill a police officer tried Thursday for a third time in as many days to commit suicide in a Manhattan courthouse. A corrections officer noticed Dennis Rogha, 28, hanging from the bars of his holding cell on the seventh floor of the courthouse. The guard quickly sliced the noose of bandages and called an ambulance. The prisoner is in stable condition Friday and awaiting a psychiatric evaluation.