Water Resources of the Caribbean
Landslides triggered by Hurricane Hugo in eastern Puerto Rico, September 1989
Matthew C. Larsen and Angel J. Torres-Sánchez
U.S. Geological Survey, GSA Center, Suite 400-15, 651 Federal Drive, Guaynabo, Puerto Rico, 00965-5703, USA
On the morning of September 18, 1989, a category-four hurricane struck eastern Puerto Rico with a sustained wind speed in excess of 46 m/s. The 24-h rainfall accumulation from the hurricane ranged from 100 to 339 mm. Average rainfall intensities ranging from 34 to 39 mm/h were calculated for 4 and 6 h periods, respectively, at a rain gage equipped with satellite telemetry, and at an observer station.
The hurricane rainfall triggered more than 400 landslides in the steeply
sloping, highly dissected mountains of eastern Puerto Rico. Of these
landslides, 285 were mapped from aerial photography which covered 6474 ha.
Many of the mapped landslides were on northeast- and northwest-facing slopes
at the eastern terminus of the mountains, nearest the hurricane path. The
surface area of individual landslides ranged from 18 m2 to 4500 m2, with a
median size of 148 m2. The 285 landslides disturbed 0.11% of the land
surface in the area covered by aerial photographs. An approximate denudation
rate of 164 mm/1000 y was calculated from the volume of material eroded by
landsliding and the 10-y rainfall recurrence interval.
Larsen, M. C., and Torres-Sánchez, A. J., 1992, Landslides triggered by Hurricane Hugo in eastern Puerto Rico, September 1989: Caribbean Journal of Science, vol. 28, no. 3-4, p. 113-125.