Authors: Carlos Ramos Scharron*, University of Texas - Austin, Abby Guidry, Environmental Science Institute
Topics: Geomorphology, Hazards, Risks, and Disasters, Water Resources and Hydrology
Keywords: hurricane, sediment budget, erosion, tropics, Caribbean
Session Type: Paper
Start / End Time: 11:10 AM / 12:25 PM
Room: Plaza Court 7, Sheraton, Concourse Level
Presentation File: No File Uploaded
Most domestic water demand in Puerto Rico (PR) is supplied through a series of reservoirs, yet sediments currently occupy about 30% of the entire water storage capacity of the island. Inadequate dredging schedules and high sediment yield rates (~1,100 Mg km-2 yr-1) are to blame. With a sediment yield of 3,170 Mg km-2 yr-1, the headwaters of Río Yauco draining towards the Lucchetti Reservoir (LR) are distinguished as having the highest yield rates in the island. About 35% of the areas upstream of LR are active cropland, mostly coffee farms. Surface erosion from active farms and unsurfaced access roads upstream from the LR amount to only about 17% of its long-term annual accumulation rate. Even though landslides dominate the sediment budgets of other areas in PR, their importance are yet unknown in its coffee growing region. Landslide scar polygon geodatabases are being developed based on aerial photography taken immediately following Hurricane María in 2017. Preliminary maps suggest an average landslide density of ~70 scars per km2, which denuded about 2% of the entire contributing area. The areal extent of each mapped landslide in combination with the elevation differences between two LiDAR-based elevation models (2016 and 2017 post-María) are being used to generate a locally-derived area-to-volume power law relationship that will aid in estimating the contribution of tropical cyclones in the sediment budget of the watershed. The results will aid in guiding erosion control management decisions focused on reservoir sedimentation for this and other similar watersheds in PR.