Abstract

Hurricane María was an extreme atmospheric event that impacted Puerto Rico in 2017. As a result of the passage of hurricane María over the island more than 70,000 landslides were triggered, with the highest density of mass wasting found in the mountainous center of the island. This area is highly susceptible to slope failure given the local soils that form as a result of continuous tropical chemical weathering of the bedrock material. Copious amounts of sediment from these soils were mobilized and transported by the landslide-triggering event. The results of our study reveal the soil types that are most susceptible to mass wasting loss in order to better understand their susceptibility to failure and contribution to sedimentation across the rugged interior of the island. A preliminary analysis of area volume scaling statistics for thousands of landslide sites in the important Lago Dos Bocas basin reveals that Hurricane María likely liberated at least 1.7 million cubic meters of mostly superficial sediment in the lake’s contributing area (not including the Caonillas sub-basin). In an effort to determine the efficiency of the fluvial system to transport these sediments during and after the catastrophic hurricane event, bathymetric surveying was carried out in Lago Dos Bocas, where much of the sediment is hypothesized to have been deposited. This reservoir is a vital piece of infrastructure in the island as it supplies water to the San Juan metropolitan area. Based on the 2021 bathymetric survey and the historical data, the excess sediment deposition to the reservoir related to Hurricane María is estimated at approximately 2.1 million cubic meters. When compared with data from 1999-2010, this volume represents the equivalent of 18 years of background sedimentation. At present, the reservoir capacity loss since construction is at 64%. These analyses are pertinent to understand how the local sediment budget has been affected and to re-calculate the useful life of the reservoir and highlight the vulnerability of Caribbean infrastructure systems, given the forecasted likelihood of increased tropical cyclone activity in the years to come.