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WFO San Juan Flood Safety Awareness

"The Hydrology of Puerto Rico is unique due to topography.  In the mountains, slopes are steep and the soil is thin.  Very little water infiltrates the soil surface, so runoff quickly turns creeks and streams into raging torrents.  Since Puerto Rico's 70 drainage basins are small, rivers rise quickly downstream and inundate the coastal plains.  In effect, almost all of these floods can be considered flash floods since the crest occurs with 6 hours following the heavy rainfall" - excerpt form the Natural Disaster Survey Report - Puerto Rico Flash Floods January 5-6, 1992

Basins in the U.S. Virgin Islands consist almost exclusively of what are locally referred to as "guts", which are dry stream beds. Even the largest drainages are dry for extended periods, filling up only during heavy rains.

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