Torres-Sierra H.

THE RAINFALL-TRIGGERED LANDSLIDE AND FLASH FLOOD DISASTER IN NORTHERN VENEZUELA, DECEMBER 1999

Larsen M.C., Wieczorek G.F., Eaton L.S., Torres-Sierra H. (2001) – The rainfall-triggered landslide and flash-flood disaster in northern Venezuela, December 1999. Proceedings of the Seventh Federal Interagency Sedimentation Conference, Reno, NV, IV, 9-16.

Abstract: 
A combination of climatologic, geologic, and demographic factors makes the Caribbean coast of Venezuela in the state of Vargas highly susceptible to episodic debris flows and flash floods. An extremely steep, tectonically active mountain front forms the boundary with a tropical sea. Easterly tradewinds can force moist air masses upslope and precipitate large rainfall volumes, creating conditions for high-magnitude debris flows and flash floods. The population of several hundred thousand people that reside at the base of the mountains is inevitably vulnerable to hydrologic disasters that seem to recur once or twice per century. The flash flood-debris flow process combination is highly destructive in populated areas. Without careful planning of human settlements, the impacts of these types of disasters are likely to increase in the future.

NATURAL HAZARDS ON ALLUVIAL FANS: THE DEBRIS FLOW AND FLASH FLOOD DISASTER OF DECEMBER 1999, VARGAS STATE, VENEZUELA

Larsen, M.C., Wieczorek, G. F., Eaton, L.S., and Torres-Sierra, H., 2001, Natural hazards on alluvial fans: the debris flow and flash flood disaster of December 1999, Vargas state, Venezuela: in W.F. Sylva (ed.), Proceedings of the Sixth Caribbean Islands Water Resources Congress, Mayagüez, Puerto Rico, February 22 and 23, 2001, unpaginated CD

Abstract: 
Large populations live on or near alluvial fans in locations such as Los Angeles, California, Salt Lake City, Utah, Denver, Colorado, and lesser known areas such as Sarno, Italy, and Vargas, Venezuela. Debris flows and flash floods occur episodically in these alluvial fan environments, and place many communities at high risk during intense and prolonged rainfall. In December 1999, rainstorms induced thousands of landslides along the Cordillera de la Costa, Vargas, Venezuela. Rainfall accumulation of 293 mm during the first 2 weeks of December was followed by an additional 911 mm of rainfall on December 14 through 16. Debris flows and floods inundated coastal communities resulting in a catastrophic death toll of as many as 30,000 people. Flash floods and debris flows caused severe property destruction on alluvial fans at the mouths of the coastal mountain drainage network. In time scales spanning thousands of years, the alluvial fans along this Caribbean coastline are dynamic zones of high geomorphic activity. Because most of the coastal zone in Vargas consists of steep mountain fronts that rise abruptly from the Caribbean Sea, the alluvial fans provide practically the only flat areas upon which to build. Rebuilding and reoccupation of these areas requires careful determination of hazard zones to avoid future loss of life and property.
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