The floods of September 6, 1960, were the greatest known on many streams in eastern Puerto Rico. There were 117 lives lost, 30 persons missing, and 136 injured. Total damage was estimated in excess of $7 million. Several thousand persons were forced from their homes by the floods as 484, houses were destroyed and more than 3,600 others were. damaged. All main highways and most secondary roads were impassable for a short period during the floods and damage to them was heavy.
Following the passage of Hurricane Donna off the northeast coast, rains of very high intensity fell over parts of the eastern half of the island, beginning about 9 p.m. September 5. By dawn September 6, rains totaling more than 10 inches over a large area produced floods in every river basin from the Rio Grande de Manati eastward. Flood discharges on the Rio Humacao, Rio Turabo, and Rio Valenciano were the greatest known and rank high among the notable floods on streams that drain from 6 to ]5 square miles.
An outstanding feature of the floods was the unusually high magnitude of peak discharges--9 of the 24 peak discharges determined had Myers ratings greater than 80 percent.