Plot and watershed-scale impacts of unpaved roads for runoff and sediment production in Culebra, Puerto Rico

Authors: Preston McLaughlin*, University of Texas - Austin
Topics: Water Resources and Hydrology, Physical Geography, Coastal and Marine
Keywords: Unpaved Roads, Puerto Rico, Hydrogeomorphology, GIS
Session Type: Paper
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Marshall North, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Terrigenous sediment delivery into tropical coastal waters from land development is a key stressor influencing the global decline of coral reef ecosystems, and Caribbean reefs are amongst the most affected. Higher turbidity of coastal waters from sediment loading rates can result in smothering, bleaching, reduced photosynthetic activity, and increased risk of disease for coral colonies. The small Puerto Rican municipality of Isla de Culebra has experienced significant rates of development since the 1990’s, which has been correlated with the continuous decline in health of coral reefs surrounding the island. This presentation focuses on quantifying runoff, and sediment production rates for unpaved road and undisturbed surfaces at the plot (3 m^2), and watershed (1 km^2) scales. Forty-seven rainfall simulations were conducted in bounded plots to collect this data. In addition, drainage points along approximately 8 kilometers of unpaved road were pinpointed while field mapping our areas of interest in Culebra. We will be extrapolating the rainfall simulation data to the road segment, and watershed scale using hydrological modeling techniques in ArcGIS. Once we have calculated infiltration capacity curves for both surface types, we can then determine which actual rainfall events produced overland runoff within the last 2 years. Pinpointing road segments that are producing the most overland runoff will be the next step in this analysis. This information will be greatly useful in determining if nearby detention ponds are large enough to effectively collect all suspended sediment being carried through overland runoff.

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