The frequency and distribution of recent landslides in three montane tropical regions of Puerto Rico

Abstract

Landslides are common in steep mountainous areas of Puerto Rico where mean annual rainfall and the frequency of intense storms are high. Each year, landslides cause extensive damage to property and occasionally result in loss of life. Average population density is high, 422 peoplerkm 2 , and is increasing. This increase in population density is accompanied by growing stress on the natural environment and physical infrastructure. As a result, human populations are more vulnerable to landslide hazards. The Blanco, Cibuco, and Coamo study areas range in surface area from 276 to 350 km 2 and represent the climatologic, geographic, and geologic conditions that typify Puerto Rico. Maps of recent landslides developed from 1:20,000-scale aerial photographs, in combination with a computerized geographic information system, were used to evaluate the frequency and distribution of shallow landslides in these areas. Several types of landslides were documentedrainfall-triggered debris flows, shallow soil slips, and slumps were most abundant. Hillslopes in the study area that have been anthropogenically modified, exceed 128 in gradient, are greater than 300 m in elevation, and face the east-northeast, are most prone to landsliding. A set of simplified matrices representing geographic conditions in the three study areas was developed and provides a basis for the estimation of the spatial controls on the frequency of landslides in Puerto Rico. This approach is an example of an analysis of the frequency of landslides that is computationally simple, and therefore, may be easily transferable to other settings. q

A spheroidal weathering model coupling porewater chemistry to soil thicknesses during steady-state denudation

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Logistic regression applied to natural hazards: rare event logistic regression with replications

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Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach

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