Smith, J. A., P. Sturdevant-Rees, M. L. Baeck, and M. C. Larsen (2005), Tropical cyclones and the flood hydrology of
Puerto Rico, Water Resour. Res., 41, W06020, doi:10.1029/2004WR003530.
Some of the largest unit discharge flood peaks in the stream gaging records of the
U.S. Geological Survey (USGS) have occurred in Puerto Rico. Many of these flood peaks
are associated with tropical cyclones. Hurricane Georges, which passed directly over the
island on 21–22 September 1998, produced record flood peaks at numerous USGS
stations in Puerto Rico. The hydrology and hydrometeorology of extreme flood response
in Puerto Rico are examined through analyses of rainfall, based on Weather Surveillance
Radar–1988 Doppler (WSR-88D) radar reflectivity observations and USGS rain gage
observations and discharge from USGS stream gaging stations. Peak rainfall
accumulations of more than 700 mm occurred in the central mountain region of the island.
The largest unit discharge flood peaks, however, were located in the eastern portion of
the island in areas with smaller storm total rainfall accumulations but markedly larger
rainfall rates at 5–60 min timescale. Orographic precipitation mechanisms played an
important role in rainfall distribution over the island of Puerto Rico. Amplification of
rainfall accumulations was associated with areas of upslope motion. Elevated low-level
cloud water content in regions of upslope motion played an important role in the
maximum rainfall accumulations in the central mountain region of Puerto Rico. The
largest unit discharge flood peaks, however, were produced by a decaying eye wall
mesovortex, which resulted in a 30–45 min period of extreme rainfall rates over the
eastern portion of the island. This storm element was responsible for the record flood peak
of the Rı´o Grande de Lo´iza. The role of terrain in development and evolution of the
eye wall mesovortex is unclear but is of fundamental importance for assessing extreme
flood response from the storm. Hydrologic response is examined through analyses of
rainfall and discharge from five pairs of drainage basins, extending from east to west over
the island. These analyses point to the importance of short-term rainfall rates for extreme
flood response. The hydrologic response of Puerto Rico is compared with two other
extreme flood environments, the central Appalachians and Edwards Plateau of Texas.
These analyses suggest that the high rainfall environment of Puerto Rico is linked to the
development of a hydraulically efficient drainage system.