Water Resources of the Caribbean
A rainfall intensity-duration threshold for landslides in a humid-tropical environment, Puerto RicoMatthew C. Larsen1 and Andrew Simon2 1U.S. Geological Survey GSA Center 651 Federal Drive Guaynabo, Puerto Rico 00965-5703, USA 2U.S. Geological Survey, Nashville, Tennessee, USA AbstractExtensive landslide damage to roads and reservoirs is common on the mountainous islands of the Caribbean basin. The landslides typically are triggered by factors such as heavy rainfall, seismic activity, or construction. The leading cause of landslides in Puerto Rico is intense and/or prolonged rainfall. Storms that triggered numerous (tens to hundreds) landslides occurred in Puerto Rico at an average rate of 1.2 per year between 1959 and 1991. A rainfall intensity/duration threshold for landsliding in the central mountains of Puerto Rico, where mean annual rainfall generally exceeds 2,000 mm, is delimited by the response to 263 storms that occurred between 1959 and 1991. Thirty six of the 263 storms produced rainfall that resulted in numerous landslides. A threshold fitted to the lower boundary of the field defined by landslide-triggering storms is expressed as
I = 91.46 D -0.82where I is rainfall intensity in mm/h, and D is duration in hours. For storms that had durations of up to 10 h, landsliding did not occur until rainfall intensity was as much as three times as high as the rainfall intensity reported as sufficient to trigger landsliding in temperate regions. As storm durations approach 100 h, the rainfall conditions necessary to initiate landsliding in Puerto Rico converge with those defined for temperate regions. A rainfall threshold provides government agencies and managers of large development projects with an important tool for hazard prediction in landslide-prone regions. A comparison of the Puerto Rico threshold with landslide and rainfall-intensity/duration data from other humid-tropical regions indicates that the threshold developed for Puerto Rico may be applicable to other environments with comparable topographic and climatologic characteristics. Larsen, M. C., and Simon, Andrew, 1992, A rainfall intensity-duration threshold for landslides in a humid-tropical environment, Puerto Rico [abs] Geological Society of America: Abstracts with programs, vol. 24, no. 7, p. A234. |
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